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Antibody blood tests not reliable enough: WHO

A recent report by the World Health Organisation (WHO) has advised against using serodiagnostic test, which is used commonly in India to diagnose tuberculosis (TB).

mumbai Updated: Mar 24, 2011 01:28 IST
Sonal Shukla

A recent report by the World Health Organisation (WHO) has advised against using serodiagnostic test, which is used commonly in India to diagnose tuberculosis (TB).

WHO’s Strategic and Technical Advisory Group for TB (STAG TB) in September 2010 recommended that the serodiagnostic test should not be used to diagnose active TB because of its poor performance and adverse impact of misdiagnosis in patients.

The study, reported in the January issue of The Lancet, a UK–based medical journal, stated that though no international guidelines recommend its use, scores of commercial serological tests for TB are being sold in India and this could worsen the TB epidemic in the country.

Most city doctors agree with the WHO report.

“Serological test, or antibody blood tests, are not sufficiently reliable to diagnose TB or rule it out with any accuracy,” said Dr Zarir Udwadia, consultant chest medicine, Hinduja Hospital.

Dr Camilla Rodrigues, consultant microbiologist, Hinduja Hospital, said that there is compelling evidence that these tests perform poorly in our setting and often give false positive results.

“Patients are then unnecessarily put on anti-TB treatment for months when it is sometimes not required,” she said.

Dr Madhukar Pai, a professor at McGill University, Montreal, and co-chair of the Stop TB Partnership's New Diagnostics Working Group, said in an e-mail that in India 1.5 million TB serological tests are done every year. “The market size of this undependable test is at least Rs 70 crore per year,” said Pai.

As TB is a rampant disease in India, anyone can get exposed to the TB bacilli. Serology Tests for TB, which only measures the antibodies against the infective organism, are marketed aggressively but may not reflect an active disease process, said doctors.

“Quite a few educated, uneducated people as well as doctors who are unaware of the efficacy of the serological test, approach us, worried about the fact that the test has come positive,” said Dr JM Joshi, professor and head of department- respiratory medicine, Nair Hospital.