Diagnostic tests for malaria underused in Zambia

Despite improvements in the ability to diagnose malaria, these diagnostic tests are often underused in Zambia, and patients with negative test results are often prescribed anti-malaria medications, according to a study in the May 23/30 issue of JAMA, a theme issue on malaria.

The recent introduction of the effective but expensive artemisinin-based (a type of medication) combination therapy for malaria throughout Africa has led to renewed interest in improving the accuracy of diagnosis. The use of rapid antigen-detection diagnostic tests (RDTs) has been proposed as an approach for reducing overtreatment of malaria. The most widely used method to confirm a diagnosis of malaria is microscopy, according to background information in the article.

Davidson H. Hamer, M.D., of the Boston University School of Public Health, Boston, and colleagues from the Zambian Ministry of Health, the Kenyan Medical Research Institute and University of Oxford, assessed the association between use of microscopy and RDT and the prescription of antimalarials in Zambia. The researchers conducted a survey, carried out between March and May 2006, of 104 government and mission health facilities in four districts in Zambia. At each facility, data were collected during one working day on ill outpatients treated at the facility.

An equipment survey in the four districts revealed that 17 percent of the 104 health facilities had functional microscopy; 63 percent had RDTs. Overall, 73 percent of health facilities had at least 1 type of malaria diagnostics available.

Of the 1,717 patients (of all ages) with fever (suspected malaria), 27.8 percent treated in health facilities with malaria diagnostics were tested and 44.6 percent had positive test results. Of patients with negative blood smear results, 58.4 percent were prescribed an antimalarials, as were 35.5 percent of those with a negative RDT result. Most patients with fever (72.6 percent) did not have any diagnostic procedure performed. Antimalarials were prescribed to 66 percent of these patients. About half of this group received artemether-lumefantrine (an artemisinin-based combination therapy).

In facilities with artemether-lumefantrine in stock, this antimalarial was prescribed to a large proportion of patients with fever with a positive diagnostic test result, but also to some with a negative diagnostic test result (blood smear, 30.4 percent; RDT, 26.7 percent).

“RDTs have been proposed as a cost-effective approach to reducing overtreatment of malaria; under current practice in Zambia, however, their use will not achieve this goal,” the authors write.

“Given the widespread increase of artemisinin-based combination therapy in sub-Saharan Africa for management of uncomplicated malaria, there is a need to limit inappropriate use of these expensive new combinations. The increasing body of evidence that a substantial proportion of febrile patients do not have malaria, especially in low to moderate transmission zones, emphasizes the need to educate health center staff on the rational use of artemisinin-based combination therapy, which will require strengthening the availability of malaria diagnostics and enhancing quality control measures so that health care providers will have confidence in the test results.”

“The RDT training program in Zambia needs to be restructured such that trainees are provided with clear instructions about how to respond to a negative test result. Without taking these steps, we may rapidly be confronted with widespread resistance of P falciparum to artemisinin-based combination therapy, and the lifespan of these highly effective new therapies will be reduced,” the authors conclude.-JAMA and Archives Journals