In a statement released last month, the WHO called for the end of commercial blood (serological) antibody-detection tests for diagnosing active tuberculosis (TB) .
The serological tests that works well for several other infectious diseases, antibody tests for TB are increasingly recognised to be inaccurate, inconsistent and of no clinical value.
The commercial serological tests are available in at least 17 of 22 countries with the highest burden of TB, including China, South Africa, Brazil, Indonesia, Nigeria, Kenya, Uganda, Afghanistan, Myanmar, Pakistan, the Russian Federation and the Philippines.
Regulation of diagnostics is weak in these countries, with the result that poorly performing tests can easily enter the market. Once there, the money to be made by stakeholders; doctors, laboratories, diagnostic companies and distributors, ensures that they are widely used, even without any policy or scientific evidence supporting such use.
But although most regulatory and guidance bodies have mechanisms in place to withdraw or ban ineffective or dangerous drugs and vaccines, there is little awareness of the consequences of poor diagnostic tests, and few safeguards in place to stop their use.
Yet misdiagnosis of TB can be harmful both to patients and to public health. For patients, it may include financial loss, unnecessary therapy (after false-positive results), or morbidity and mortality after false-negative tests fail to pick up the disease. From a public health perspective, every missed TB diagnosis may result in additional transmission.
Until recently, the TB community was not aware of the magnitude of the use, and therefore the potential misuse of serological tests.
The study found that, as an initial test for active TB among adults, serology results in more human suffering, secondary infections and false-positive diagnoses than the more conventional sputum-smear microscopy tests, while also increasing costs per patient.
Last month's statement issued by WHO, which is based on these two studies and additional advice from experts, concludes that "the quality of evidence for commercial serodiagnostic tests was very low, with harms/risks far outweighing any potential benefits ".
It therefore recommends that these tests "should not be used in individuals suspected of active pulmonary or extra-pulmonary TB, irrespective of their HIV status", although the WHO policy does not discourage research to develop improved or novel serological tests for TB.
It is now up to high-burden countries to implement the policy by tightening their regulations, and by educating doctors, laboratories and consumers on the need to prevent the continued misuse of such diagnostics.
WHO statement criticising serological TB testing
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