Simpler approach to TB testing
Wednesday July 13th, 2011
Improved tests for tuberculosis can be used effectively in poorer countries, British researchers said today.
In 2008, nine million people developed tuberculosis (TB) and 1.7 million died from the disease. More than 90 per cent of cases were in low- and middle-income countries.
Dr Luis Cuevas of the Liverpool School of Tropical Medicine, UK, and colleagues looked at alternative approaches to diagnosis.
Most patients in are investigated by a method that needs a sputum specimen at one appointment, one produced the following morning, and one at the next appointment. This can be highly effective, but many patients do not return for their second visit.
The team examined whether schemes that collect specimens on only one day could be a viable alternative. They enrolled 6,627 patients in Ethiopia, Nepal, Nigeria and Yemen who were tested for tuberculosis due to a cough lasting more than two weeks.
A sputum collection scheme where two samples were collected one hour apart, followed by a morning specimen, identified just as many TB cases as the standard two-day scheme. Results also showed that testing the first two specimens alone identified most cases.
Writing in PLoS Medicine, the authors say: "The sensitivity and specificity of 'spot-spot-morning' are non-inferior to those of 'spot-morning-spot', with a higher proportion of patients submitting specimens. The scheme identifies most smear-positive patients on the first day of consultation."
They believe that this approach "has the potential to improve the diagnosis of pulmonary tuberculosis in Low and Middle-Income Countries".
"A single-visit diagnosis would represent a substantial opportunity to improve the delivery of TB services, particularly to the poor," they conclude.
The experts also showed that a faster laboratory test called light emitting-diode fluorescence microscopy (LED-FM) identified more cases than the standard smear microscopy test.
Cuevas, L. E. et al. LED Fluorescence Microscopy for the Diagnosis of Pulmonary Tuberculosis: A Multi-Country Cross-Sectional Evaluation. PLoS Med 8(7): e1001057.
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