**5. Conclusion**

films [15]. The findings on chest CT which could represent an active disease or disease complications include features suggestive of consolidation, fibrosis, cavitations and honey combing [15]. Similarly, the chest CT provides a clearer view of extra-pulmonary involvement of *Mycobacterium tuberculosis* infection. For example a "tree in bud" appearance on chest CT sufficiently represents active disease which may not be discernible on x-ray films [15]. Despite, the added advantage of chest CT over chest x-ray, microbiological test for *Mycobacterium tuberculosis* is essential

Tuberculin skin test for the latent tuberculosis is an ancient molecular investigation that still reserves a place in clinical practice [30]. A major drawback of tuberculin skin test is its inability to differentiate the latent tuberculosis from an active disease. This diagnostic drawback has a therapeutic and prognostic implication. Line probe assay and Cephid GeneXpert System are the other advanced molecular investigations that have enabled detection of drug resistant tuberculosis [30]. Cephid GeneXpert System has been recommended as the first choice tuberculosis investigation especially among suspected cases of multidrug resistant disease [34, 35]. This decision may have been predicated on the suitability of Cephid GeneXpert System for use in resource limited environment due to its adequate sensitivity, specificity and the minimal technical knowhow for its operation

[34, 35]. However, this guideline should be cautiously recommended for developing

Lipoarabinomannan (LAM) assay in urine has been commercially available for over 20 years but its deployment for use in tuberculosis diagnostics is slow [36]. This molecular investigation is a point-of-care assay that enables detection of LAM which is a mycobacterial cell wall glycolipid antigen [36, 37]. Lipoarabinomannan assay in urine has enabled diagnosis of disseminated tuberculosis especially in pauci-bacillary state and among HIV patients. A meta-analytic study has reported a

nations because they may not cope with its financial implication.

sub-optimal sensitivity for LAM assay in urine [38]. However, subsequent

this molecular investigation improved its sensitivity, specificity and cost-

improvement in LAM assay in urine by way of development of strip test version of

Immunological investigations for active tuberculosis include nucleic acid amplification tests and bacteriophage-based tests. These immunological investigations have allowed detection of nucleic acid sequence of *Mycobacterium tuberculosis* and assisted in genetic finger typing [28–30]. In furtherance, immunological methods of *Mycobacterium tuberculosis* diagnosis provide an opportunity for the infective organism speciation (MicroSeq 500 system, AccuProbe assay) and drug sensitivity test [30]. Worthy of mention in the deployment of immunological investigation for multidrug resistance evaluation are assessment of the rpoB gene mutation for rifampicin resistance, the inhA gene and the katG gene mutation for low and high

In contrast to smear microscopy/culture, nucleic acid amplification test has a greater positive predictive value (>95%), increase specificity and ability for rapid confirmation of infection [15]. Nevertheless, the smear microscopy/culture still has relevance in modern clinical practice because of its high sensitivity and utility when

drug sensitivity test of second line anti-tuberculosis is required [15].

for a definitive diagnosis.

*Healthcare Access - Regional Overviews*

*4.3.3 Molecular methods*

effectiveness.

**108**

*4.3.4 Immunological methods*

level isoniazid resistance, respectively [30, 39].

In conclusion, there is need to complement and replace where necessary the conventional tuberculosis diagnostics with advanced cutting-edge microbiological, imaging, molecular and immunologic investigations for prompt and adequate diagnosis. The diagnostic and therapeutic advantages of advanced methods of mycobacteria detection call for its speedy deployment to priority areas to enhance accuracy and efficiency of clinical evaluation. The cost of procurement and maintenance of this advanced methods of tuberculosis diagnosis maybe beyond the reach of the health care systems of nations with high burden by tuberculosis. Hence, the reason why donor funding is crucial in provision and maintenance of advanced molecular and immunological tuberculosis diagnostics in high disease burden areas especially in sub-Saharan Africa [40, 41].
