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Diagnostic tests for active tuberculosis (TB) based on the detection of antibodies (serological tests) have been commercially available for decades, although no international guidelines have recommended their use. An estimated 1.5 million serological TB tests, mainly enzyme-linked immunosorbent assays, are performed in India alone every year, mostly in the private sector. The cost of serological tests in India is conservatively estimated at US $15 million (825 million) per year. Findings from systematic reviews on the diagnostic accuracy of serological tests for both pulmonary and extra-pulmonary TB suggest that these tests are inaccurate and imprecise. A cost-effectiveness modelling study suggests that, if used as a replacement test for sputum microscopy, serology would increase costs to the Indian TB control sector approximately 4-fold and result in fewer disability-adjusted life years averted and more false-positive diagnoses. After considering all available evidence, the World Health Organization issued a strong recommendation against the use of currently available commercial serological tests for the diagnosis of TB disease. The expanding evidence base continues to demonstrate that the harms/risks of serological tests far outweigh the benefits. Greater engagement of the private sector is needed to discontinue the use of serological tests and to replace these tests with WHO-endorsed new diagnostics in India. The recent ban on import or sale of TB serological tests by the Indian health ministry is a welcome step in the right direction. [ABSTRACT FROM AUTHOR]

Undiagnosed and mismanaged tuberculosis (TB) continues to fuel the global TB epidemic. Rapid, accurate and early diagnosis of TB is therefore a priority to improve TB case detection and interrupt transmission. Although considerable improvements have been made in TB diagnostics, there are two major gaps in the existing diagnostics pipeline: (1) lack of a simple accurate point-of-care test that can be used for rapid diagnosis at the primary care level; (2) lack of a biomarker (or combination of biomarkers) that can be used to identify latently infected individuals who will benefit most from preventive therapy. Currently available commercial serological (antibody detection) tests are inaccurate and do not improve patient outcomes. Despite this evidence, dozens of serological tests are sold and used in countries (e.g. India) with weak regulatory systems, especially in the private sector. Recognizing the threat posed by these suboptimal tests, a World Health Organization (WHO) Expert Group has strongly recommended against the use of serological tests for the diagnosis of pulmonary and extra-pulmonary TB. Another WHO Expert Group has discouraged the use of interferon-γ release assays for active pulmonary TB diagnosis in low- and middle-income countries. All existing tests for latent TB infection appear to have only modest predictive value and further research is needed to identify highly predictive biomarkers. Copyright © 2011 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Based on a systematic review, Madhukar Pai and colleagues conclude that none of the commercial immune-based tests for pulmonary tuberculosis so far evaluated perform well enough to replace sputum smear microscopy. [ABSTRACT FROM AUTHOR]