Commercial serological tests for the diagnosis of active tuberculosis in India

India accounts for one fifth of the global TB burden – a total of 9.2 million new cases and 1.7 million deaths every year1,2. There are two main components of effective TB control programme: the rapid and sensitive diagnosis of the disease and containment of its spread to the uninfected population. The sputum smear microscopy, still a backbone of TB diagnosis, is less sensitive and can miss half of the pulmonary TB cases. The conventional culture method which uses egg based medium (Lowenstein-Jensen, L-J) is time consuming and lacks desirable detection level. Liquid automated culture methods, such as Bactec-MGIT (BD, USA) and MB-Bact (Biomerieux, France) have highly improved detection rates, comparatively much faster (median detection time 10-24 days) but are costly requiring air handling and infection control measures1. Molecular methods such as polymerase chain reaction (PCR) and its modified versions have come as boon in the diagnosis of tuberculosis. Despite the limitation of detecting dead bacilli, PCR is rapid (report can be made available on the same day) and precise, depending on the gene sequences targeted and protocols used. These methods can be used on various clinical samples such as sputum, tissue biopsies, cerebrospinal and other body fluids, lymph nodes and other tissue aspirates, urine, faeces, etc1. In resource limited settings like India, tuberculosis detection rates are suboptimal mainly because the diagnosis is usually made by less sensitive tools such as sputum microscopy and chest X-rays. The poor detection rates lead to mismanagement of infectious cases and possibility of drug resistance development. However, non-availability of affordable, rapid and precise diagnostic tools at peripheral level have led to mushrooming of commercial serological tests2–4. Extensive reviews and meta-analyses have concluded that the presently available antibody detection based serological tests are no good for the diagnosis of tuberculosis while helpful for other diseases. In view of this, the WHO has recently issued an advisory2. This editorial provides an academic overview of the issue.