**6. Immunological methods**

Immunodiagnostic tests can provide indirect evidence current or past infections of MTB. Ex‐ ception of tuberculin skin test, immunodiagnostic tests are of limited application due to cross reactivity and poor sensitivity.

#### **6.1. Detection of antibodies**

Although the detection of antibodies against MTB in the blood is a relatively simple and costeffective method, recent meta-analyses and systematic reviews concluded that commer‐ cial serological tests provided inconsistent results [23,24]. As the overall test performance and data quality of these assays were poor, the WHO currently recommends against their use for the diagnosis of pulmonary and extrapulmonary TB.

**8. The future of TB diagnostics**

**Concept phase Feasibility**


**phase**

colorimetric DST

Antibody detection Antigen detection

LFI sensitivity increase: Alternative quantitative fluorescence (LFI) sensitivity increase

as given Table 1 [28].

Reference laboratory level

Disrtict/peripheral level

Community level LFI sensitivity

gy has very promising.

ment of TB detection/read-out assays.

increase

**9. Assays being developed/evaluated**

The rapid technological evolution in the laboratory diagnosis of TB, especially in the ap‐ plication of molecular biology h as diminished the time required for identification and susceptibility testing. Continuous effort endeavor for increasing reproducibility, improv‐ ment of performance and cost containment. WHO founded an organisation (FIND-Foun‐ dation for Innovative New Diagnostics) for researching fast, relible and inexpensive tests

> **Devolapment phase**

Beta lactamase detection

**Table 1. WHO projects for TB diagnostic tests.** LAMP TB: Loop mediated isothermal amplification (LAMP) for TB

Another new approach to diagnosis of TB is biosensing technologies. Variety of portable, rapid, and sensitive biosensors with immediate "on-the-spot" interpretation have been de‐ veloped for MTB detection based on different biological elements recognition systems and basic signal transducer principles. Combination of nanotechnology and biosensing technolo‐

Transrenal DNA detection provides a challenging new target for molecular TB diagnosis. No commercial assays are currently available, largely due to the difficulties in the develop‐

Combined high-resolution melting (HRM) curve analysis using a closed-tube RT-PCR is po‐ tentially an ideal screening method with a positive predictive value (PPV) of 100% and neg‐

**Evaluation phase**



assay /2nd line drugs)

**Demonstration phase**

Laboratory Diagnosis of Tuberculosis – Latest Diagnostic Tools

http://dx.doi.org/10.5772/54248

147


**Implementation phase**

DST Rapid speciation Line probe assay (1st line drugs)

microscopy Xpert MTB/RIF

LAMP TB LED florecence

Antibodies against lipoarabinomannans, A60, 38Kd and 16 Kd are mostly studied [25].

### **6.2. Detection of antigens**

Lipoarabinomannan (LAM) was identified as a promising target for antigen detection for TB diagnosis due to its temperature stability and could be detected in urine. LAM-based assays are currently being developed by a number of commercial companies, and preliminary re‐ sults indicate their potential applicability in the rapid diagnosis of TB by detecting LAM in a variety of body fluids, including urine [26]. LAM-based assays are included in the WHO TB diagnosis re-tooling programme [27] and forma part of a Foundation for Innovative New Diagnostics (FIND) funded TB Project [19,28].

MTB antigen detection provides direct evidence of TB. Such as LAM, 65Kd, 14 Kd antigens were widely used. It is very quick and easy to perform. Main limitation is low sensitivity (detect high levels of antibody). It does not rule out TB in patients with poor antibody re‐ sponse as in HIV and malnutrition and not specific due to cross reactivity with other species of mycobacteria in the environment [26].
