There is a new diagnostic test for tuberculosis, but, while it's faster and more accurate than older methods, it may not make any difference to treatment outcomes, according to an early trial.
The GeneXpert MTB/RIF Assay test looks for the DNA markers of tuberculosis and can give an accurate result within two hours. This stands in stark contrast to traditional TB tests, which require trained lab technicians and are often inconclusive or slow.
Samples have to be cultured in a laboratory, and can take around eight weeks to produce a definitive result.
The new test, on the other hand, is fully automated, and simply involves slotting a cartridge into a machine. It is easy to use and, as well as diagnosing the patient, can show whether their particular strain of TB is drug-resistant.
Unfortunately, despite backing from the WHO and funding from the Global Fund to Fight AIDS, Tuberculosis and Malaria, the test is still expensive and requires a cool, sterile environment (impossible to obtain in many rural clinics).
Researchers from the University of Cape Town therefore conducted a trial in four African countries to assess the pros and cons. The findings were mixed. When diagnosed via GeneXpert, more TB patients were able to start treatment right away but, in the long term, they fared no differently from the control group.
"Considering these results, the substantial financial burden of the Xpert MTB/RIF rollout needs to be reassessed to see if it provides value for the cost," said Christian Wejse of Aarhus University, in a comment in The Lancet.
