New Delhi, July 20: Indias health ministry has issued an unprecedented warning against the use of blood tests to detect antibodies to tuberculosis widely used in the private health care sector despite abundant evidence that they are unreliable and may endanger patients lives.
The health ministry plans to circulate its advisory against the tests to medical associations across India amid concerns that about 1.5 million patients suspected to be infected by TB are taking the unnecessary tests each year on recommendations of private practitioners.
Indias decision to warn the public about the blood tests for active TB disease follows a scientific review by the World Health Organisation (WHO) and a similar first-ever negative policy advisory from the WHO urging countries to ban the blood tests.
Its sad that such tests with no predictive value at all are so widely used in our private sector, said Ashok Kumar, the head of the TB division in the health ministry. The tests are considered unreliable as they lead to unacceptably high levels of false positive and false negative results.
False positive results would mean patients may be treated and become exposed to medications and their risks without reason, while false negative results may lead to patients with TB being denied the treatment they urgently need, Kumar said.
The WHO, which had commissioned a rigorous 12-month long analysis of the blood tests for active TB disease, has said that there is overwhelming evidence to confirm the earlier observations about the unreliability of the tests.
These tests are almost exclusively used in developing countries where regulatory mechanisms are weak and where there is a market fuelled by ignorance and financial incentives for companies and distributors that sell the tests, doctors who recommend them and pathological laboratories that offer them, said Madhukar Pai, associate professor of epidemiology at McGill University in Montreal, Canada, who had generated a part of the evidence that led to the advisory from the WHO.
Patients are the only losers in this game, Pai told The Telegraph in a telephone interview. The tests used in India typically cost several hundred rupees, but their misleading results could lead to patients being wrongly diagnosed.
Indias TB control programme estimates that about 1.9 million people get active TB disease in the country each year. About 1.5 million of these patients are diagnosed and treated by the TB control programme, but many of even this set of patients first approach private doctors.
But the WHO as well as national TB control officials have been worried that private doctors in developing countries recommend the unreliable blood tests to anyone with suspicious symptoms — from patients with prolonged cough to women with infertility problems.
The antibodies to TB that these tests look for do not in any way reflect the true status of the active disease, said Pai. For reliable diagnosis, you need to actually see the bacteria, grow the bacteria, or confirm their presence through tests that look for their genes, he said.
A senior WHO official said the WHO is calling for a ban on the use of the blood tests to diagnose TB in the best interests of patients. A blood test for diagnosing active TB is bad practice — test results are inconsistent, imprecise and put patients lives in danger, Mario Raviglione, director of WHOs Stop TB department said in a statement issued from Geneva today.
The WHO said there are at least 18 of these blood tests in the market today. Most of these are manufactured in Europe and North America, although the tests have not been approved by any recognised regulatory agency. The Indian Academy of Paediatrics has also recommended against the use of antibody TB tests for diagnosis of active disease.
The WHO also said that blood tests that look for inactive TB infection — also called dormant TB — are currently under review.