**3.1. Concepts from the natural history of disease**

The pre-chemotherapy literature documented the natural history of tuberculosis in children. Unfortunately, clinicians and researchers have limited access to these important studies as they were conducted before 1950 and are not included in modern electronic databanks. Since the discovery of safe and effective antituberculosis treatment, conducting studies on the natural history of disease became unethical and therefore these historic disease descriptions remain invaluable today. The pre-chemotherapy literature provides a strong body of evidence; multiple studies monitored large cohorts of children for prolonged periods of time and carefully documented the development of disease after primary infection with Mycobacterium tuberculosis. A critical review of the natural history of disease identified three central concepts that are important to consider when addressing current and/or future challenges in the field of childhood tuberculosis: (1) the need for accurate case definitions, (2) the importance of risk stratification, and (3) the diverse spectrum of disease pathology, which necessitates accurate disease classification (Marais et al., 2004).

#### **3.2. Challenge of case definition**

Accurate case definition revolves mainly around the ability to differentiate primary infection from active disease. Primary infection is believed to occur when a previously uninfected child inhales a single infectious aerosol droplet, which may contain fewer than five bacilli that penetrate into a terminal airway. A localized pneumonic process, referred to as the primary parenchymal (Ghon) focus, results at the site of organism deposition. For the first 4–6 weeks, unrestrained multiplication occurs within the Ghon focus and bacilli drain via local lymphatics to the regional lymph nodes and beyond. The upper lobes drain to ipsilateral–paratracheal nodes, whereas the rest of the lung drains to perihilar and subcarinal nodes, with dominant lymph flow from left to right (Marais et al., 2006). The Ghon complex is represented by both the Ghon focus, with or without some overlying pleural reaction, and the affected regional lymph nodes (Marais et al., 2006).

Occult dissemination frequently occurs during this early proliferative phase before cellmediated immunity is fully activated. Bacteriologic cultures collected at this time may be positive; Wallgren demonstrated in the 1930s that M. tuberculosis is sometimes recovered from recently infected children who are not diseased. Therefore, with active contact tracing and aggressive screening that includes the collection of mycobacterial cultures in asymptomatic children it is not unexpected to find some positive cultures in recently infected children who are not diseased. This illustrates the overlap that exists between recent primary infection and case definitions of disease that rely exclusively on bacteriology. It is important to consider this overlap when case definitions are formulated for research purposes, particularly within the contact setting, although it is less relevant in everyday practice where there is no reason to obtain cultures from completely asymptomatic children.

within a community, Marais et al., 2005) including multi-drug resistant (MDR) (Schaaf et al.,

**3. Challenges presented by paediatric TB in the field of diagnosis and**

The pre-chemotherapy literature documented the natural history of tuberculosis in children. Unfortunately, clinicians and researchers have limited access to these important studies as they were conducted before 1950 and are not included in modern electronic databanks. Since the discovery of safe and effective antituberculosis treatment, conducting studies on the natural history of disease became unethical and therefore these historic disease descriptions remain invaluable today. The pre-chemotherapy literature provides a strong body of evidence; multiple studies monitored large cohorts of children for prolonged periods of time and carefully documented the development of disease after primary infection with Mycobacterium tuberculosis. A critical review of the natural history of disease identified three central concepts that are important to consider when addressing current and/or future challenges in the field of childhood tuberculosis: (1) the need for accurate case definitions, (2) the importance of risk stratification, and (3) the diverse spectrum of disease pathology, which necessitates accurate

Accurate case definition revolves mainly around the ability to differentiate primary infection from active disease. Primary infection is believed to occur when a previously uninfected child inhales a single infectious aerosol droplet, which may contain fewer than five bacilli that penetrate into a terminal airway. A localized pneumonic process, referred to as the primary parenchymal (Ghon) focus, results at the site of organism deposition. For the first 4–6 weeks, unrestrained multiplication occurs within the Ghon focus and bacilli drain via local lymphatics to the regional lymph nodes and beyond. The upper lobes drain to ipsilateral–paratracheal nodes, whereas the rest of the lung drains to perihilar and subcarinal nodes, with dominant lymph flow from left to right (Marais et al., 2006). The Ghon complex is represented by both the Ghon focus, with or without some overlying pleural reaction, and the affected regional

Occult dissemination frequently occurs during this early proliferative phase before cellmediated immunity is fully activated. Bacteriologic cultures collected at this time may be positive; Wallgren demonstrated in the 1930s that M. tuberculosis is sometimes recovered from recently infected children who are not diseased. Therefore, with active contact tracing and aggressive screening that includes the collection of mycobacterial cultures in asymptomatic children it is not unexpected to find some positive cultures in recently infected children who are not diseased. This illustrates the overlap that exists between recent primary infection and

2006) and extensively drug resistant (XDR) strains.

380 Tuberculosis - Current Issues in Diagnosis and Management

**3.1. Concepts from the natural history of disease**

disease classification (Marais et al., 2004).

**3.2. Challenge of case definition**

lymph nodes (Marais et al., 2006).

**treatment**

Uncomplicated hilar adenopathy remains the most common disease manifestation in children and is usually regarded as the hallmark of primary tuberculosis. However, the prechemother‐ apy literature documented transient hilar adenopathy in the majority (50–60%) of children after recent primary pulmonary infection, of whom only a few progressed to disease (Marais et al., 2004). The natural history of disease illustrates that progression to disease is indicated by the onset of persistent, nonremitting symptoms, referred to as the breakpoint of clinical significance whereas the complete absence of symptoms usually indicates good organism containment (Marais et al., 2004). By convention, asymptomatic hilar adenopathy is currently treated as active disease, although early experience with isoniazid alone demonstrated that one-drug therapy was sufficient in these cases. In terms of pathophysiology, microbiology, and natural history, asymptomatic hilar adenopathy is more indicative of recent primary infection than active disease (Marais et al., 2004).

This indicates that radiologic signs should be interpreted with caution in the absence of clinical data. The entity of so-called asymptomatic tuberculosis, where the case definition rests exclusively on radiographic criteria, is a case in point. High-resolution computed tomography is the most sensitive tool available to detect hilar adenopathy (Andronikou et al., 2004), as demonstrated by the fact that in children with recent M. tuberculosis infection and a normal chest radiograph, prominent intrathoracic nodes are frequently demonstrated by highresolution computed tomography. Particular caution is required when interpreting the relevance of these radiologic signs in the absence of clinical data. It is important to point out that there is no role for high-resolution computed tomography in the evaluation of asympto‐ matic, immune-competent children exposed to M. tuberculosis.

In reality, differences in patient selection may result in the use of different functional case definitions even though the definitions appear similar on paper. In non-endemic areas where active contact tracing is diligently enforced, more children with transient radiologic signs indicative of recent primary infection will be identified, and those with active disease will be diagnosed at an earlier, less advanced stage. Active contact tracing is rarely enforced in endemic areas and children usually present to health care facilities with suspicious symptoms and more advanced disease (Marais et al., 2006). Unlike asymptomatic contacts in which visible radiologic signs probably indicate recent primary infection only, radiologic signs in sympto‐ matic children indicate active disease. From a research perspective it is important to be aware of these differences, as inconsistent case definitions may confound the scientific interpretation of results. In everyday practice, distinguishing between the signs and symptoms of recent primary infection and active disease is less relevant in high-risk children (less than 3 years of age and/or immune compromised) in whom infection frequently progresses to disease, sometimes with rapid disease progression.

#### **3.3. Problems of risk stratification**

The natural history of disease demonstrates that age is the most important variable that determines the risk to progress to disease after primary M. tuberculosis infection in immunecompetent children (Marais et al., 2004). Infants are at the highest risk (Marais et al., 2004) and the risk drops but stays appreciable in the second year of life, to reach its lowest level in children infected between 5 and 10 years of age (Marais et al., 2004). Children with human immuno‐ deficiency virus (HIV) infection and/or other forms of immune compromise, such as severe malnutrition, seem to experience a similar high risk as the very young (less than 2 years of age), immune-immature children (Marais et al., 2004). The vast majority (more than 95%) of children who progress to disease do so within 12 months of primary infection and, therefore, it seems prudent to categorize all children less than 3 years of age and/or immune-compro‐ mised children as high-risk. Because of the frequency and rapidity with which disease progression may occur, exposure to and/or infection with M. tuberculosis warrants treatment intervention in this high-risk group (Marais et al., 2004).

only as children enter into puberty (Marais et al., 2004). It is important to remember that children with adult-type disease are frequently sputum smear–positive and that they do contribute to disease transmission (Cegielski and McMurray, 2004), particularly in congregate

Peadiatric Tuberculosis: Is the World Doing Enough?

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383

Complications that arise from affected lymph nodes are most common in children less than 5 years old, because of exuberant lymph node enlargement and small airway size (Marais et al., 2004). Extraluminal compression results when the airway is encircled by enlarged lymph nodes and associated inflammatory edema (Marais et al., 2004). Intraluminal obstruction results from polyps or granulomatous tissue that develops secondary to inflammatory changes in the bronchial wall, or when caseous material is deposited into an airway after lymph node eruption (Marais et al., 2004). Radiologic signs vary from segmental or lobar hyperinflation with partial obstruction and a check-valve effect (Marais et al., 2004), to segmental or lobar collapse with total obstruction and resorption of distal air (Marais et al., 2004). The pathology that results from the aspiration of caseous material is influenced by the dose and virulence of the bacilli aspirated. The pathology may range from transient parenchymal consolidation, resulting from a pure hypersensitivity response to dead bacilli and/or toxic products, to an expansile pneumonic process with progressive caseating pneumonia in the affected segment or lobe (Marais et al., 2004). Expansible caseating pneumonia frequently leads to parenchymal

Thus, cavitary disease in children may result from three distinct pathologic processes: (1) poor containment at the site of organism deposition (very young and/or immune-compromised children); (2) aspiration of live bacilli when a diseased lymph node erupts into an airway, with destructive caseating pneumonia in the distal segment or lobe (children less than 5 year of age); and (3) adult-type disease (mainly children greater than 10 year of age). The fact that immune-competent children 5 to 10 yr of age experience the lowest risk to progress to disease after primary infection with M. tuberculosis is an interesting immunologic phenomenon that is poorly understood. A better understanding of age-related differences in the immune response to M. tuberculosis may provide important insight into immune correlates of disease

Disseminated disease occurs predominantly in very young (immune-immature) and/or immune-compromised children, such as the HIV-infected or severely malnourished (Pai et al., 2004; Shingadia and Chen, 2004). These children have suboptimal cellular immune responses and demonstrate poor containment of the organism, both within the regional lymph nodes and at the multiple sites of occult dissemination. TB meningitis (TBM) is the most dangerous

Diagnostic difficulties pose the greatest challenge to childhood TB management (Marais and Pai, 2007). There are diagnostic complications because: (i) TB can mimic many common child‐ hood diseases, including pneumonia, generalized bacterial and viral infections, malnutrition,

complication of disseminated disease, occurring in 20 to 30% of cases (Chen, 2004).

settings such as schools.

destruction and cavity formation.

and protection.

**3.5. Challenges in diagnosis**

*3.5.1. Overview of diagnostic challenges*

Immune-competent children of at least 3 years of age are at low risk of progression to disease after primary infection. However, as the vast majority of children in endemic areas become infected after 2 to 3 years of age, these low-risk children still contribute a significant percentage to the total disease burden. In addition, although these children are at low risk to progress to disease, latent infection with M. tuberculosis does pose the risk of future reactivation of the disease. In non-endemic areas, where transmission rates are low and eradicating the pool of latent infection is an achievable aim, the provision of preventive therapy to these low-risk children is warranted. In endemic areas, where the majority of disease in immune-competent adults results from ongoing transmission and not from reactivation (Saiman et al., 2001), the provision of preventive therapy after exposure and/or infection becomes less relevant. The major diagnostic challenge in this low-risk group is the differentiation between latent infection and active disease (Marais et al., 2004). Fortunately, active disease is accompanied by persis‐ tent, non-remitting symptoms and disease progression is slow, which provides a window of opportunity for symptom-based diagnosis (Marais et al., 2004).

#### **3.4. Difficulties in classifying disease diversity**

Childhood tuberculosis is often reported as a single disease entity, although it represents a diverse spectrum of pathology (Marais et al., 2004), and one of the obstacles has been the lack of standard descriptive terminology. Accurate disease classification is important, because of its prognostic significance and to facilitate scientific communication and optimal case man‐ agement. Within the Ghon focus, containment is usually successful, but disease progression may result from either poor or "excessive" containment. Poor containment and unrestrained organism proliferation may cause progressive parenchymal damage, with ultimate break‐ down of the Ghon focus. Infants (Dinnes et al., 2007) and HIV-positive children (Pai et al., 2004), who have poor cell-mediated immune responses, are most vulnerable to this type of cavitation. In contrast, immune-competent adolescents seem to mount an "excessive" (dam‐ aging) immune response in an attempt to contain the organism. The exact immune mechanisms underlying adult-type disease remain uncertain, but it is a striking observation that it emerges only as children enter into puberty (Marais et al., 2004). It is important to remember that children with adult-type disease are frequently sputum smear–positive and that they do contribute to disease transmission (Cegielski and McMurray, 2004), particularly in congregate settings such as schools.

Complications that arise from affected lymph nodes are most common in children less than 5 years old, because of exuberant lymph node enlargement and small airway size (Marais et al., 2004). Extraluminal compression results when the airway is encircled by enlarged lymph nodes and associated inflammatory edema (Marais et al., 2004). Intraluminal obstruction results from polyps or granulomatous tissue that develops secondary to inflammatory changes in the bronchial wall, or when caseous material is deposited into an airway after lymph node eruption (Marais et al., 2004). Radiologic signs vary from segmental or lobar hyperinflation with partial obstruction and a check-valve effect (Marais et al., 2004), to segmental or lobar collapse with total obstruction and resorption of distal air (Marais et al., 2004). The pathology that results from the aspiration of caseous material is influenced by the dose and virulence of the bacilli aspirated. The pathology may range from transient parenchymal consolidation, resulting from a pure hypersensitivity response to dead bacilli and/or toxic products, to an expansile pneumonic process with progressive caseating pneumonia in the affected segment or lobe (Marais et al., 2004). Expansible caseating pneumonia frequently leads to parenchymal destruction and cavity formation.

Thus, cavitary disease in children may result from three distinct pathologic processes: (1) poor containment at the site of organism deposition (very young and/or immune-compromised children); (2) aspiration of live bacilli when a diseased lymph node erupts into an airway, with destructive caseating pneumonia in the distal segment or lobe (children less than 5 year of age); and (3) adult-type disease (mainly children greater than 10 year of age). The fact that immune-competent children 5 to 10 yr of age experience the lowest risk to progress to disease after primary infection with M. tuberculosis is an interesting immunologic phenomenon that is poorly understood. A better understanding of age-related differences in the immune response to M. tuberculosis may provide important insight into immune correlates of disease and protection.

Disseminated disease occurs predominantly in very young (immune-immature) and/or immune-compromised children, such as the HIV-infected or severely malnourished (Pai et al., 2004; Shingadia and Chen, 2004). These children have suboptimal cellular immune responses and demonstrate poor containment of the organism, both within the regional lymph nodes and at the multiple sites of occult dissemination. TB meningitis (TBM) is the most dangerous complication of disseminated disease, occurring in 20 to 30% of cases (Chen, 2004).

#### **3.5. Challenges in diagnosis**

**3.3. Problems of risk stratification**

382 Tuberculosis - Current Issues in Diagnosis and Management

intervention in this high-risk group (Marais et al., 2004).

opportunity for symptom-based diagnosis (Marais et al., 2004).

**3.4. Difficulties in classifying disease diversity**

The natural history of disease demonstrates that age is the most important variable that determines the risk to progress to disease after primary M. tuberculosis infection in immunecompetent children (Marais et al., 2004). Infants are at the highest risk (Marais et al., 2004) and the risk drops but stays appreciable in the second year of life, to reach its lowest level in children infected between 5 and 10 years of age (Marais et al., 2004). Children with human immuno‐ deficiency virus (HIV) infection and/or other forms of immune compromise, such as severe malnutrition, seem to experience a similar high risk as the very young (less than 2 years of age), immune-immature children (Marais et al., 2004). The vast majority (more than 95%) of children who progress to disease do so within 12 months of primary infection and, therefore, it seems prudent to categorize all children less than 3 years of age and/or immune-compro‐ mised children as high-risk. Because of the frequency and rapidity with which disease progression may occur, exposure to and/or infection with M. tuberculosis warrants treatment

Immune-competent children of at least 3 years of age are at low risk of progression to disease after primary infection. However, as the vast majority of children in endemic areas become infected after 2 to 3 years of age, these low-risk children still contribute a significant percentage to the total disease burden. In addition, although these children are at low risk to progress to disease, latent infection with M. tuberculosis does pose the risk of future reactivation of the disease. In non-endemic areas, where transmission rates are low and eradicating the pool of latent infection is an achievable aim, the provision of preventive therapy to these low-risk children is warranted. In endemic areas, where the majority of disease in immune-competent adults results from ongoing transmission and not from reactivation (Saiman et al., 2001), the provision of preventive therapy after exposure and/or infection becomes less relevant. The major diagnostic challenge in this low-risk group is the differentiation between latent infection and active disease (Marais et al., 2004). Fortunately, active disease is accompanied by persis‐ tent, non-remitting symptoms and disease progression is slow, which provides a window of

Childhood tuberculosis is often reported as a single disease entity, although it represents a diverse spectrum of pathology (Marais et al., 2004), and one of the obstacles has been the lack of standard descriptive terminology. Accurate disease classification is important, because of its prognostic significance and to facilitate scientific communication and optimal case man‐ agement. Within the Ghon focus, containment is usually successful, but disease progression may result from either poor or "excessive" containment. Poor containment and unrestrained organism proliferation may cause progressive parenchymal damage, with ultimate break‐ down of the Ghon focus. Infants (Dinnes et al., 2007) and HIV-positive children (Pai et al., 2004), who have poor cell-mediated immune responses, are most vulnerable to this type of cavitation. In contrast, immune-competent adolescents seem to mount an "excessive" (dam‐ aging) immune response in an attempt to contain the organism. The exact immune mechanisms underlying adult-type disease remain uncertain, but it is a striking observation that it emerges

#### *3.5.1. Overview of diagnostic challenges*

Diagnostic difficulties pose the greatest challenge to childhood TB management (Marais and Pai, 2007). There are diagnostic complications because: (i) TB can mimic many common child‐ hood diseases, including pneumonia, generalized bacterial and viral infections, malnutrition, and HIV (Marais and Pai, 2007); (ii) the absence of a practical reference test or gold standard (Marais et al., 2006); (iii) of the inability of child patients to expectorate sputum (Nelson and Wells, 2004) (iv) of the nonspecific clinical presentation (Nicol. et al., 2009); (v) of the lower ba‐ cillary load in children which is often smear negative (Detjen et al., 2007) (vi) confirmation by culture of Mycobacterium tuberculosis, usingthe gold standard of diagnosis in adult TB, rare‐ ly exceeds 30–40% sensitivity (although it may be considerably higher in children with ad‐ vanced disease) (Hesseling et al., 2002) even when using gastric aspirates, induced sputum, liquid media, and polymerase chain reaction (PCR) (Edwards et al., 2007); vii) distinguishing between recent primary infection and active disease is highly difficult (Gomez-Pastrana et al., 2001); viii) gastric aspirates continue to be the best specimens for testing for suspected pulmo‐ nary TB in children (Ling et al., 2011) with 30–40% sensitivity (Hesseling et al., 2002).

children with TB are never diagnosed or registered as cases of TB (Nelson and Wells, 2004). Furthermore, the consequences of missed diagnosis in children are severe, as untreated children have a high probability of developing active TB, usually within two years of infection

Peadiatric Tuberculosis: Is the World Doing Enough?

http://dx.doi.org/10.5772/54953

385

The difficulty to obtain samples for TB diagnosis in children has led researchers to create smart approaches as "la cuerda dulce" (sweet string), reported by Chow et al., (2006). They provide a technique which consists of a coiled nylon string inside a gel capsule. The string unravels through a hole in the end of the weighted capsule as it descends into the stomach and the capsule then dissolves in it, allowing the string to become coated with gastrointestinal secretions containing whatever pathogens are present. After about four hours, the capsule is passed in the feces. This methodology is well tolerated by children and is less invasive than

In addition to poor bacteriologic yields, the collection of bacteriologic specimens is often problematic. Two or three fasting gastric aspirates collected on consecutive days, usually requiring hospital admission, are routinely performed in young children who cannot cough up phlegm. A retrospective study from California compared the bacteriologic yield achieved in gastric aspirates collected from hospitalized and nonhospitalized children. Although the yield in hospitalized children was higher (percentage of positive cultures, 48 compared to 37%), this difference was not statistically significant, which suggests that hospitalization may not be a prerequisite for the collection of a good gastric aspirate specimen. Bronchoalveolar lavage, using flexible fiberoptic bronchoscopy, has additive value when used in combination with gastric lavage, but this technique is highly specialized and is unavailable in most endemic areas. In a study from Peru, midmorning nasopharyngeal aspiration was compared with early morning gastric aspiration; gastric aspiration provided a slightly better yield than nasophar‐ yngeal aspiration (38 compared to 30%), but the results were comparable (Nelson et al., 2004). Nasopharyngeal aspiration is minimally invasive, does not require hospitalization or fasting, and can be performed any time of the day. A study from South Africa demonstrated that a single specimen, using hypertonic saline–induced sputum collection, may provide the same yield as three gastric aspirate specimens (Corbett et al., 2003). However, the overall yield in this study remained poor (15% with one and 20% with three induced sputum specimens) and the technique has not been used outside the hospital setting. Additional studies are awaited to confirm the feasibility and diagnostic value of collecting induced sputum specimens in

Because of the difficulty in achieving bacteriologic confirmation, the diagnosis of childhood tuberculosis in non- endemic areas is usually based on (1) known contact with an adult index case (frequently within the household), (2) a positive tuberculin skin test (TST), and (3) suggestive signs on the chest radiograph. This triad provides a fairly accurate diagnosis in settings where exposure to M. tuberculosis is rare and well documented. However, its diagnostic accuracy is greatly reduced in endemic areas where exposure to M. tuberculosis is common and often undocumented, as exposure frequently occurs outside the household. Despite reservations about the specificity of the TST response after Bacille Calmette-Guérin (BCG) vaccination and/or exposure to environmental mycobacteria, a positive TST reaction

the gastrointestinal lavage (López Ávalos and Montes de Oca, 2012).

(López Ávalos and Montes de Oca, 2012).

primary health care settings.

Bacteriologic confirmation, the accepted gold standard, is of limited use in children because of the paucibacillary nature of their disease and poor bacteriologic yields. Sputum smear microscopy, often the only diagnostic test available in endemic areas, is positive in less than 10 to 15% of children with probable tuberculosis (Schaaf et al., 2006). However, the yield is high in children with adult-type disease and sputum smear microscopy has definite diagnostic value in older children (more than 10 year of age) (Cegielski and McMurray, 2004). Culture yields are also low; reported yields in children with probable tuberculosis are less than 30 to 40% (Schaaf et al., 2006). However, the bacteriologic yield depends on the specific intrathoracic disease manifestation. A study from South Africa reported a yield of 77% in children with advanced intrathoracic disease, whereas the yield in those with uncomplicated hilar adenop‐ athy was only 35% (odds ratio, 6.3; 95% confidence interval, 3.2–12.8) (Graham et al., 2001). This indicates the potential value of sensitive bacteriology-based diagnostic approaches, particularly in endemic areas where children frequently present with advanced disease.

Most children with TB are classified as smear-negative pulmonary TB (PTB) for the reasons mentioned above, which is an inappropriate term as a smear or culture has not usually been done. This leads to difficulties in determining the true extent of PTB in children in different areas and circumstances. Extrapulmonary TB (EPTB) accounts for up to 20–30% of the total caseload of TB in children, and the diagnosis is usually easier than PTB because of the characteristic clinical features like lymphadenopathy with or without scrofula, spinal deform‐ ity, disseminated disease, meningitis, effusions (pleural or pericardial), or painless ascite (Lewinsohn et al., 2004). The isolation of Mycobacterium tuberculosis takes several weeks. Consequently, the diagnosis of TB in children is often supported only by epidemiological, clinical, and radiographic findings in the presence of a positive tuberculin skin test (López Ávalos and Montes de Oca, 2012).

The value of the classic diagnostic is based on: (1) exposure to an adult index case; (2) chronic respiratory symptoms that do not respond to broad-spectrum antibiotics; (3) documented weight loss or failure to thrive; (4) a positive tuberculin skin test (TST); (5) the presence of suggestive signs on the chest radiograph (CXR), which is greatly reduced in endemic areas where exposure to and/or infection with M. tuberculosis is common (Marais et al., 2006). These criteria are less helpful in endemic areas where a positive TST result is common and exposure to M. tuberculosis is often undocumented (Hesseling et al., 2002). For all these reasons, many children with TB are never diagnosed or registered as cases of TB (Nelson and Wells, 2004). Furthermore, the consequences of missed diagnosis in children are severe, as untreated children have a high probability of developing active TB, usually within two years of infection (López Ávalos and Montes de Oca, 2012).

and HIV (Marais and Pai, 2007); (ii) the absence of a practical reference test or gold standard (Marais et al., 2006); (iii) of the inability of child patients to expectorate sputum (Nelson and Wells, 2004) (iv) of the nonspecific clinical presentation (Nicol. et al., 2009); (v) of the lower ba‐ cillary load in children which is often smear negative (Detjen et al., 2007) (vi) confirmation by culture of Mycobacterium tuberculosis, usingthe gold standard of diagnosis in adult TB, rare‐ ly exceeds 30–40% sensitivity (although it may be considerably higher in children with ad‐ vanced disease) (Hesseling et al., 2002) even when using gastric aspirates, induced sputum, liquid media, and polymerase chain reaction (PCR) (Edwards et al., 2007); vii) distinguishing between recent primary infection and active disease is highly difficult (Gomez-Pastrana et al., 2001); viii) gastric aspirates continue to be the best specimens for testing for suspected pulmo‐

nary TB in children (Ling et al., 2011) with 30–40% sensitivity (Hesseling et al., 2002).

Bacteriologic confirmation, the accepted gold standard, is of limited use in children because of the paucibacillary nature of their disease and poor bacteriologic yields. Sputum smear microscopy, often the only diagnostic test available in endemic areas, is positive in less than 10 to 15% of children with probable tuberculosis (Schaaf et al., 2006). However, the yield is high in children with adult-type disease and sputum smear microscopy has definite diagnostic value in older children (more than 10 year of age) (Cegielski and McMurray, 2004). Culture yields are also low; reported yields in children with probable tuberculosis are less than 30 to 40% (Schaaf et al., 2006). However, the bacteriologic yield depends on the specific intrathoracic disease manifestation. A study from South Africa reported a yield of 77% in children with advanced intrathoracic disease, whereas the yield in those with uncomplicated hilar adenop‐ athy was only 35% (odds ratio, 6.3; 95% confidence interval, 3.2–12.8) (Graham et al., 2001). This indicates the potential value of sensitive bacteriology-based diagnostic approaches, particularly in endemic areas where children frequently present with advanced disease.

Most children with TB are classified as smear-negative pulmonary TB (PTB) for the reasons mentioned above, which is an inappropriate term as a smear or culture has not usually been done. This leads to difficulties in determining the true extent of PTB in children in different areas and circumstances. Extrapulmonary TB (EPTB) accounts for up to 20–30% of the total caseload of TB in children, and the diagnosis is usually easier than PTB because of the characteristic clinical features like lymphadenopathy with or without scrofula, spinal deform‐ ity, disseminated disease, meningitis, effusions (pleural or pericardial), or painless ascite (Lewinsohn et al., 2004). The isolation of Mycobacterium tuberculosis takes several weeks. Consequently, the diagnosis of TB in children is often supported only by epidemiological, clinical, and radiographic findings in the presence of a positive tuberculin skin test (López

The value of the classic diagnostic is based on: (1) exposure to an adult index case; (2) chronic respiratory symptoms that do not respond to broad-spectrum antibiotics; (3) documented weight loss or failure to thrive; (4) a positive tuberculin skin test (TST); (5) the presence of suggestive signs on the chest radiograph (CXR), which is greatly reduced in endemic areas where exposure to and/or infection with M. tuberculosis is common (Marais et al., 2006). These criteria are less helpful in endemic areas where a positive TST result is common and exposure to M. tuberculosis is often undocumented (Hesseling et al., 2002). For all these reasons, many

Ávalos and Montes de Oca, 2012).

384 Tuberculosis - Current Issues in Diagnosis and Management

The difficulty to obtain samples for TB diagnosis in children has led researchers to create smart approaches as "la cuerda dulce" (sweet string), reported by Chow et al., (2006). They provide a technique which consists of a coiled nylon string inside a gel capsule. The string unravels through a hole in the end of the weighted capsule as it descends into the stomach and the capsule then dissolves in it, allowing the string to become coated with gastrointestinal secretions containing whatever pathogens are present. After about four hours, the capsule is passed in the feces. This methodology is well tolerated by children and is less invasive than the gastrointestinal lavage (López Ávalos and Montes de Oca, 2012).

In addition to poor bacteriologic yields, the collection of bacteriologic specimens is often problematic. Two or three fasting gastric aspirates collected on consecutive days, usually requiring hospital admission, are routinely performed in young children who cannot cough up phlegm. A retrospective study from California compared the bacteriologic yield achieved in gastric aspirates collected from hospitalized and nonhospitalized children. Although the yield in hospitalized children was higher (percentage of positive cultures, 48 compared to 37%), this difference was not statistically significant, which suggests that hospitalization may not be a prerequisite for the collection of a good gastric aspirate specimen. Bronchoalveolar lavage, using flexible fiberoptic bronchoscopy, has additive value when used in combination with gastric lavage, but this technique is highly specialized and is unavailable in most endemic areas. In a study from Peru, midmorning nasopharyngeal aspiration was compared with early morning gastric aspiration; gastric aspiration provided a slightly better yield than nasophar‐ yngeal aspiration (38 compared to 30%), but the results were comparable (Nelson et al., 2004). Nasopharyngeal aspiration is minimally invasive, does not require hospitalization or fasting, and can be performed any time of the day. A study from South Africa demonstrated that a single specimen, using hypertonic saline–induced sputum collection, may provide the same yield as three gastric aspirate specimens (Corbett et al., 2003). However, the overall yield in this study remained poor (15% with one and 20% with three induced sputum specimens) and the technique has not been used outside the hospital setting. Additional studies are awaited to confirm the feasibility and diagnostic value of collecting induced sputum specimens in primary health care settings.

Because of the difficulty in achieving bacteriologic confirmation, the diagnosis of childhood tuberculosis in non- endemic areas is usually based on (1) known contact with an adult index case (frequently within the household), (2) a positive tuberculin skin test (TST), and (3) suggestive signs on the chest radiograph. This triad provides a fairly accurate diagnosis in settings where exposure to M. tuberculosis is rare and well documented. However, its diagnostic accuracy is greatly reduced in endemic areas where exposure to M. tuberculosis is common and often undocumented, as exposure frequently occurs outside the household. Despite reservations about the specificity of the TST response after Bacille Calmette-Guérin (BCG) vaccination and/or exposure to environmental mycobacteria, a positive TST reaction remains a fairly accurate measure of M. tuberculosis infection in immune-competent children. Current U.S. guidelines recommend the use of three different cutoff points to define a positive TST reaction. In endemic areas a positive TST is not uncommon in randomly selected healthy children (Jeena et al., 2002), which limits its diagnostic value. Consequently, the diagnosis of tuberculosis in children from endemic areas depends mainly on clinical features and the subjective interpretation of the chest radiograph (Marais et al., 2007). However, chest radiog‐ raphy is unavailable in many endemic areas and it has well-known limitations that may result in both under- and overdiagnosis of disease (Brent et al., 2007). Despite these limitations it provides an accurate diagnosis in the majority of symptomatic children with tuberculosis and the interpretation of the chest radiograph remains the most widely used diagnostic criterion in clinical practice (Palme et al., 2002).

symptoms, while the potential window for symptom-based diagnosis is limited by the rapidity with which disease progression may occur. Chest radiograph interpretation is complicated by HIV-related comorbidity and atypical disease presentation. These difficulties increase the potential diagnostic value of sensitive bacteriology-based approaches, to identify HIV-infected children with tuberculosis (Upham et al., 2002). However, as HIV-infected children are in the high-risk group the detection of M. tuberculosis infection is also highly relevant. Disease progression may occur soon (less than 12 months) after primary or reinfection, or latent infection may be reactivated at a later date because of a decline in immunity. The traditional TST has poor sensitivity to detect M. tuberculosis infection in HIV-infected children; 50% or less of HIV-infected children with bacteriologically confirmed tuberculosis are TST positive, despite using an induration size of at least 5 mm (Upham et al., 2002). This is a major limitation and development of a more reliable measure of infection will be valuable to identify HIVinfected children who may benefit from preventive chemotherapy; it may also provide

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LTBI, in children as in adults, lacks a diagnostic gold standard. The diagnosis is usually pursued after a documented household exposure, or to evaluate if chemoprophylactic therapy is indicated in the context of immunosuppression. In this setting, pre-existing MTB specific host immune responses are measured to confirm previous infection. Data in adults have confirmed that IGRA are more sensitive and specific than the TST (Pai et al., 2004; Ferrara et al., 2006) in this context. Preliminary data suggest IGRA also perform better in children but age-related data are still sparse. Longitudinal studies assessing their positive predictive value for the development of active TB are required in both TB-endemic and low-incidence countries, as the continued exposure in TB endemic settings might yield very different results, compared

There were an estimated 0.5 million adult cases of MDR-TB in 2007. By the end of 2008, 55 countries and territories had reported at least 1 case of extensively drug-resistant TB (WHO Report, 2009). Latest research reports published in The Lancet at the end of August 2012, indicate that researchers have found rates of both multi drug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) higher than previously thought and that they are threatening global efforts to curb the spread of TB. They contend that most international recommendations for TB control have been developed for MDR-TB prevalence of up to around 5 percent but that now the world faces a prevalence up to 10 times higher in some places, where almost half of the patients are transmitting MDR strains. The Researchers who studied rates of the disease in Estonia, Latvia, Peru, the Philippines, Russia, South Africa, South Korea, and Thailand are reported to have found that almost 44 percent of cases of MDR TB were also

Comprehensive studies on resistance to anti-TB drugs in children are lacking, because they are not included in global surveys. Surveillance of anti-TB drug resistance during 1995–2007

to the "one-off" exposure more typically encountered in non-endemic countries.

resistant to at least one second-line drug outline goes here (Dalton et al., 2012)

supportive evidence to establish a diagnosis of active tuberculosis.

*3.5.2. Challenges presented by diagnosis of latent infection in children*

**3.6. Challenges presented by drug resistance**

Various clinical scoring systems have been developed. A critical review of these clinical scoring systems concluded that they are limited by a lack of standard symptom definitions and adequate validation (Walls and Shingadia, 2007). Developing standard symptom definitions through consensus of expert opinion is a difficult and subjective exercise; better guidance may be provided by objectively measuring the potential diagnostic value of different symptom definitions. A community-based survey demonstrated that the poorly defined symptoms traditionally associated with tuberculosis (such as a cough greater than 3 weeks in duration) are frequently reported in a random selection of healthy children (Bryce et al., 2005). Of 1,397 children without tuberculosis, 253 (26.4%) reported a cough during the preceding 3 months and 66 (6.9%) reported a cough greater than 3 weeks in duration (Bryce et al., 2005). In addition, nearly 50% of children with visible hilar adenopathy on the chest radiograph (diagnosed with tuberculosis) reported no symptoms at all (Bryce et al., 2005). These observations demonstrate the limited diagnostic value of poorly defined symptoms and the need for improved symptom and case definitions. In a follow-on study the use of well-defined symptoms with a persistent, nonremitting character showed greatly improved diagnostic accuracy (Scot et al., 2008). However, the potential diagnostic value offered by the use of these well-defined symptoms requires further validation in a prospective, community-based study that includes children from all relevant risk groups. It is expected that symptom-based diagnostic approaches would have less value in high-risk children (less than 3 years of age and/or immune compromised) where disease progression may occur rapidly, emphasizing the need for preventive chemo‐ therapy and early diagnosis of disease in this group (Chintu, et al., 2002). Other diagnostic modalities may hold promise, but have not shown convincing results to date (WHO, 2006).

Serologic tests are currently unable to diagnose childhood tuberculosis with accuracy, and sputum-based polymerase chain reaction (PCR) tests have shown variable results and limited utility (WHO, 2007). Good results were reported with the use of a heminested PCR technique in Peru, but the study used uninfected children as the control group and therefore could not evaluate the ability of this novel PCR-based test to differentiate latent infection from active disease (Upham et al., 2006), which is important, as specific concerns have been raised regarding the specificity of PCR-based tests.

The diagnostic dilemma is even more pronounced in HIV-infected children. The specificity of symptom-based diagnostic approaches is reduced by the presence of chronic HIV-related symptoms, while the potential window for symptom-based diagnosis is limited by the rapidity with which disease progression may occur. Chest radiograph interpretation is complicated by HIV-related comorbidity and atypical disease presentation. These difficulties increase the potential diagnostic value of sensitive bacteriology-based approaches, to identify HIV-infected children with tuberculosis (Upham et al., 2002). However, as HIV-infected children are in the high-risk group the detection of M. tuberculosis infection is also highly relevant. Disease progression may occur soon (less than 12 months) after primary or reinfection, or latent infection may be reactivated at a later date because of a decline in immunity. The traditional TST has poor sensitivity to detect M. tuberculosis infection in HIV-infected children; 50% or less of HIV-infected children with bacteriologically confirmed tuberculosis are TST positive, despite using an induration size of at least 5 mm (Upham et al., 2002). This is a major limitation and development of a more reliable measure of infection will be valuable to identify HIVinfected children who may benefit from preventive chemotherapy; it may also provide supportive evidence to establish a diagnosis of active tuberculosis.

#### *3.5.2. Challenges presented by diagnosis of latent infection in children*

LTBI, in children as in adults, lacks a diagnostic gold standard. The diagnosis is usually pursued after a documented household exposure, or to evaluate if chemoprophylactic therapy is indicated in the context of immunosuppression. In this setting, pre-existing MTB specific host immune responses are measured to confirm previous infection. Data in adults have confirmed that IGRA are more sensitive and specific than the TST (Pai et al., 2004; Ferrara et al., 2006) in this context. Preliminary data suggest IGRA also perform better in children but age-related data are still sparse. Longitudinal studies assessing their positive predictive value for the development of active TB are required in both TB-endemic and low-incidence countries, as the continued exposure in TB endemic settings might yield very different results, compared to the "one-off" exposure more typically encountered in non-endemic countries.

#### **3.6. Challenges presented by drug resistance**

remains a fairly accurate measure of M. tuberculosis infection in immune-competent children. Current U.S. guidelines recommend the use of three different cutoff points to define a positive TST reaction. In endemic areas a positive TST is not uncommon in randomly selected healthy children (Jeena et al., 2002), which limits its diagnostic value. Consequently, the diagnosis of tuberculosis in children from endemic areas depends mainly on clinical features and the subjective interpretation of the chest radiograph (Marais et al., 2007). However, chest radiog‐ raphy is unavailable in many endemic areas and it has well-known limitations that may result in both under- and overdiagnosis of disease (Brent et al., 2007). Despite these limitations it provides an accurate diagnosis in the majority of symptomatic children with tuberculosis and the interpretation of the chest radiograph remains the most widely used diagnostic criterion

Various clinical scoring systems have been developed. A critical review of these clinical scoring systems concluded that they are limited by a lack of standard symptom definitions and adequate validation (Walls and Shingadia, 2007). Developing standard symptom definitions through consensus of expert opinion is a difficult and subjective exercise; better guidance may be provided by objectively measuring the potential diagnostic value of different symptom definitions. A community-based survey demonstrated that the poorly defined symptoms traditionally associated with tuberculosis (such as a cough greater than 3 weeks in duration) are frequently reported in a random selection of healthy children (Bryce et al., 2005). Of 1,397 children without tuberculosis, 253 (26.4%) reported a cough during the preceding 3 months and 66 (6.9%) reported a cough greater than 3 weeks in duration (Bryce et al., 2005). In addition, nearly 50% of children with visible hilar adenopathy on the chest radiograph (diagnosed with tuberculosis) reported no symptoms at all (Bryce et al., 2005). These observations demonstrate the limited diagnostic value of poorly defined symptoms and the need for improved symptom and case definitions. In a follow-on study the use of well-defined symptoms with a persistent, nonremitting character showed greatly improved diagnostic accuracy (Scot et al., 2008). However, the potential diagnostic value offered by the use of these well-defined symptoms requires further validation in a prospective, community-based study that includes children from all relevant risk groups. It is expected that symptom-based diagnostic approaches would have less value in high-risk children (less than 3 years of age and/or immune compromised) where disease progression may occur rapidly, emphasizing the need for preventive chemo‐ therapy and early diagnosis of disease in this group (Chintu, et al., 2002). Other diagnostic modalities may hold promise, but have not shown convincing results to date (WHO, 2006).

Serologic tests are currently unable to diagnose childhood tuberculosis with accuracy, and sputum-based polymerase chain reaction (PCR) tests have shown variable results and limited utility (WHO, 2007). Good results were reported with the use of a heminested PCR technique in Peru, but the study used uninfected children as the control group and therefore could not evaluate the ability of this novel PCR-based test to differentiate latent infection from active disease (Upham et al., 2006), which is important, as specific concerns have been raised

The diagnostic dilemma is even more pronounced in HIV-infected children. The specificity of symptom-based diagnostic approaches is reduced by the presence of chronic HIV-related

in clinical practice (Palme et al., 2002).

386 Tuberculosis - Current Issues in Diagnosis and Management

regarding the specificity of PCR-based tests.

There were an estimated 0.5 million adult cases of MDR-TB in 2007. By the end of 2008, 55 countries and territories had reported at least 1 case of extensively drug-resistant TB (WHO Report, 2009). Latest research reports published in The Lancet at the end of August 2012, indicate that researchers have found rates of both multi drug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) higher than previously thought and that they are threatening global efforts to curb the spread of TB. They contend that most international recommendations for TB control have been developed for MDR-TB prevalence of up to around 5 percent but that now the world faces a prevalence up to 10 times higher in some places, where almost half of the patients are transmitting MDR strains. The Researchers who studied rates of the disease in Estonia, Latvia, Peru, the Philippines, Russia, South Africa, South Korea, and Thailand are reported to have found that almost 44 percent of cases of MDR TB were also resistant to at least one second-line drug outline goes here (Dalton et al., 2012)

Comprehensive studies on resistance to anti-TB drugs in children are lacking, because they are not included in global surveys. Surveillance of anti-TB drug resistance during 1995–2007 among children from South Africa showed a significant increase in resistance to INH or RIF from 6.9% to 15.1% and an increase in multidrug resistance from 2.3% to 6.7% (Schaaf et al., 2009). Drug resistance among children has been documented in clinical trials of both pulmo‐ nary and extrapulmonary TB (Rekha and Swaminathan, 2007). Management of MDR-TB is a challenge, because it requires prolonged treatment for 24 months with second-line drugs, which are more toxic and expensive than first-line drugs. According to the 2006 WHO guidelines for programmatic management of MDR-TB, an optimal regimen should include a fluoroquinolone, an injectable (capreomycin, kanamycin, or amikacin), and at least 2 of the following drugs: cycloserine, thiomides, para-amino salicylic acid, and first-line agents other than INH and RIF (WHO, 2008). Experience with second-line TB drugs in children is limited; 38 children in Peru were treated with supervised, individualized regimens consisting of 5 drugs in the national program. Despite half of these children being anemic and malnourished, treatment was well tolerated and resulted in a 95% cure rate (Drobac et al., 2006).

(Kalantri et al., 2005). This represents laudable progress, particularly in the context of increas‐ ing drug resistance. Calorimetric culture systems such as the TK medium (Kocagoz et al., 2004) and electronic-nose technology (Fend et al., 2006) are also under investigation. Among adults MODS appears to be at least as sensitive as gold standard liquid culture methods (Moore et al., 2006), Data comparing its performance in children is more limited, but MODS has been evaluated in a paediatric hospital setting and found to be more sensitive than solid media in one study (Oberhelman et al., 2006). Data validating other new methods in paediatric speci‐ mens are also lacking, yet performance may be affected by the paucibacillary nature of childhood TB. The lowest limit of detection of TB by the electronic nose for example has been reported to be 104 CFU/ml of sputum for example which is just within the range of the expected bacillary burden in paediatric specimens (Fend et al., 2006). Validation of these assays on paediatric samples is a research priority (López Ávalos G G and Montes de Oca, 2012). The introduction of GeneXpert which includes use of integrated DNA extraction and amplification systems and utilizes real-time PCR (rt-PCR) technology to both diagnose TB and detect rifampicin resistance, has given a ray of hope with paediatric TB diagnosis and rifampicin

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The use of well-defined symptoms improves diagnostic accuracy of pulmonry tuberculo‐ sis (PTB) (Imaz et al., 2001). With clinical symptoms approach only, the status can be classified in two; suspected TB or probable TB. Two situations lead the clinician to sus‐ pect that a child has tuberculosis. The first is a history of chronic illness with clear symp‐ toms: cough and/or fever, weight loss or failure to thrive, an inability to return to normal health after measles or whooping cough, fatigue, and wheezing; second, is when one or more of the following: malnutrition, lymphadenopathy, chest signs, hepatomegaly and/or splenomegaly, meningeal signs, and/or ascites is/are observed. For probable TB, in addi‐ tion to suspected TB, the child presents with a positive TST, a suggestive radiological chest appearing as pleural effusion, caseation of biopsy material, poor response to 2 weeks of antibiotic treatment, and/or favourable response to antituberculous treatment

In pediatric TB, the most common symptoms are pulmonary parenchymal disease and intrathoracic adenopathy accounting for 60–80% of all cases. Among extrapulmonary mani‐ festations, lymphadenopathy is the most common (67%), followed by central nervous system involvement (13%), pleural (6%), miliary and/or disseminated TB (5%), and skeletal TB form (4%). Disseminated disease and TB meningitis are usually found in very young children who are below the age of 3 years, and/or HIV-infected children (Nelson et al., 2004). TB meningitis

resistance (Gordetsov et al., 2008).

**4.1. Classical diagnosis**

*4.1.1. Clinical symptoms approach*

**4. Diagnosis and treatment: Current state of affairs**

(weight gain and loss of signs) (Hesseling et al., 2002).

occurs when the child has contact with a suspected or confirmed case.

There is little published information on optimal treatment of latent TB infection in children in contact with patients with MDR-TB. In a 30-month follow-up of contacts of patients with MDR-TB, 5% of children who received appropriate chemoprophylaxis and 20% of those who did not receive prophylaxis developed disease (Schaaf et al., 2007). Regimens used included INH, PZA, and ethionamide or EMB. Currently, the best approach may be to perform a complete risk assessment and clinical evaluation and to individualize therapy, while keeping these children under close observation. Multicentric trials are urgently required to determine the most effective drug combinations and optimal duration of chemoprophylaxis for contacts of patients with MDR-TB.

TB is often not considered in the differential diagnosis in children, especially in low endemic settings. TB can mimic many common childhood diseases, including pneumonia, generalised bacterial and viral infections, malnutrition and HIV. However, the main impediment to the accurate diagnosis of active TB is the paucibacillary nature (containing just a few bacilli) of the disease in children. Younger children also produce smaller amounts of sputum, which is usually swallowed rather than expectorated. Bacteriological samples may be collected by conducting early morning gastric washings, a fairly unpleasant procedure that requires hospital admission and overnight-fast for up to three consecutive nights. Consequently bacteriological confirmation is the exception rather than the rule with only 10-15 % of sputum samples revealing acid fast bacilli (AFB) and culture remaining negative in around 70% of cases with probable TB (Zar et al., 2005). Without a definitive diagnosis treatment is therefore often initiated on clinical judgment, aided by algorithms based on exposure history, clinical features, chest x-ray (CXR) and TST (Marais et al., 2006). Several approaches have been taken to improve the diagnosis (Marais and Pai, 2007).

#### **3.7. Improving bacteriological detection and rapid resistance analysis**

Recent advances in bacteriological and molecular methods for the detection of MTB in patient samples aim to identify drug-resistance in parallel with detection of MTB. These include the Microscopic Observation Drug Susceptibility assay (MODS) (Moore et al., 2006), more sensitive PCR techniques (Sarmiento et al., 2003) or phage-based tests such as FASTPlaque (Kalantri et al., 2005). This represents laudable progress, particularly in the context of increas‐ ing drug resistance. Calorimetric culture systems such as the TK medium (Kocagoz et al., 2004) and electronic-nose technology (Fend et al., 2006) are also under investigation. Among adults MODS appears to be at least as sensitive as gold standard liquid culture methods (Moore et al., 2006), Data comparing its performance in children is more limited, but MODS has been evaluated in a paediatric hospital setting and found to be more sensitive than solid media in one study (Oberhelman et al., 2006). Data validating other new methods in paediatric speci‐ mens are also lacking, yet performance may be affected by the paucibacillary nature of childhood TB. The lowest limit of detection of TB by the electronic nose for example has been reported to be 104 CFU/ml of sputum for example which is just within the range of the expected bacillary burden in paediatric specimens (Fend et al., 2006). Validation of these assays on paediatric samples is a research priority (López Ávalos G G and Montes de Oca, 2012). The introduction of GeneXpert which includes use of integrated DNA extraction and amplification systems and utilizes real-time PCR (rt-PCR) technology to both diagnose TB and detect rifampicin resistance, has given a ray of hope with paediatric TB diagnosis and rifampicin resistance (Gordetsov et al., 2008).
