August 2011: Dr Mario Raviglione, Director of the Stop TB Department is calling for an end to using serological tests to diagnose tuberculosis, because it is now considered bad practice, as test results are imprecise, inconsistent and are putting patients’ lives in danger and impeding TB control efforts.

Why is it so difficult to test for active tuberculosis by detecting antibodies in the blood? Patients can have different antibody responses that suggest they have TB even though they do not. Antibodies can also develop against other organisms which could again give the false impression that an individual has TB. It is also complicated by the fact that different organisms share the same antigens, which make test results unreliable.

The World Health Organization’s Special Programme for Research and Training in Tropical Diseases (TDR) has been studying this issue for five years with its partners including the University of California San Francisco, McGill University and the University of Washington. Dr Andy Ramsay of TDR wonders whether governments will be encouraged to act and stop using poor TB diagnostics knowing that undiagnosed cases and mis-diagnosis of TB increases transmission of this disease which is spread by cough or sneeze, which infects the lungs.

Newly published studies indicate that there are two other methods that could be used to test for tuberculosis that would be more convenient and accessible for those in low- and middle-income countries.

One study suggests that a sputum collection scheme in which two samples are collected one hour apart followed by a morning specimen could identity smear-positive patients. This would be better for patients who currently have to return over a period of several days for samples to be taken and which many skip. The adoption of the “same-day” scheme could also help improve diagnosis of TB.

The other study shows that there is a more sensitive and faster tool than the traditional light microscopes to examine sputum: a light-emitting diode fluorescence microscope (of LED-FM). However, proper training is essential to maintain the same level of accuracy. Therefore, the WHO has recently recommended that conventional fluorescence microscopy be replaced by LED microscopy, and that LED microscopy be phased in as an alternative for conventional Ziehl-Neelsen light microscopy. 

Among ILEP Members who support TB work are the German Leprosy and Tuberculosis Relief Association, Damien Foundation Belgium, LEPRA Health in Action and FAIRMED, whilst there are other ILEP Members that help finance some of the anti-TB activities of other ILEP Members.

 

Categories: Technical information