Rapid diagnostic tests for malaria effective as long as clinical responses are consistent

This authors of this study, published in The British Medical Journal point out that, although rapid diagnostic tests for malaria seem cost effective, the standard analyses of these tests do not take into account clinicians responses to the test results.

Working in Tanzania, they used a clinical trial of 2425 patients in three areas with varying levels of malaria transmission. They examined the relation between the level of response consistent with results of parasitological tests and the total costs resulting from the use of rapid diagnostic tests and microscopy. Previous studies in Zambia have found that where rapid diagnostic tests are used routinely in settings where microscopy is not available, antimalarials continued to be prescribed to over a third of patients who had negative test results. In Tanzania, a recent randomised trial of rapid diagnostic tests compared with blood slide testing found that in low transmission areas, over 90% of all antimalarials prescribed were given to patients with a negative test result, irrespective of the test method used. These levels of overprescribing extend also to patients with severe illness.

This study found that, at moderate levels of transmission, rapid diagnostic tests were more cost effective than microscopy and both were more cost effective than presumptive treatment, but only where the response was consistent with test results. They also found that microscopy becomes more cost beneficial than rapid diagnostic tests when its sensitivity under operational conditions approaches that of rapid diagnostic tests.