Diagnosis of tuberculosis: the experience at a specialized diagnostic laboratory

None of the tests we evaluated can accurately detect the presence or absence of Mycobacterium tuberculosis in all the samples and smear microscopy was found to be the most reliable assay in this study.The PCR assay could detect down to 2 pg of H37Rv DNA. Sensitivity, specificity was 0.40, 0.60 and 0.19, 0.81 for smear positive (n = 228) and negative samples (n = 235) respectively. In the MODS assay, sensitivity, specificity of 0.48, 0.52 and 0.38, 0.76 was observed for smear positive and negative samples. Sputum smear microscopy had sensitivity of 0.77 and specificity of 0.70.Despite the availability of effective and inexpensive therapy, tuberculosis (TB) is one of the leading causes of death from an infectious disease. It is believed that the clinical management of TB is made more difficult by the lack of a simple and effective diagnostic test. Correct and timely diagnosis of TB is very important to achieve higher compliance with the treatment, reduce transmission and to reduce the development of drug resistance.Along with the emergence of evidence based diagnosis approaches [1], a number of new technologies have been introduced [2]. These include light-emitting diode (LED)-based fluorescence microscopy [3], automated liquid culture systems such as BacT/ALERT MP [4], interferon-gamma release assays [5], etc.Recently published meta-analysis and reviews make us to believe that the future of TB diagnosis is bright. On the other hand, WHO and other organizations such as FIND (Geneva) perpetually call proposals for the development of simple and cost effective tests for TB diagnosis. This suggests that the current scenario is far from satisfactory and not all the claims made by the researchers and companies regarding the sensitivity and specificity etc. of the TB diagnostic tests are valid in actual 'field conditions'.We carried out an evaluation of relatively new TB diagnosis technologies. In addition to the direct sputum microscopy, we performed nucleic acid detection