Serological tests for the diagnosis of active tuberculosis: relevance for India

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.