Following Zambia’s decision to scale up the provision of new diagnostic tools in concert with improving malaria case-management with new, expensive ACT within a year, 63% of health facilities had RDTs available for use and over 73% of facilities had either RDTs or microscopy available for malaria diagnosis. However only 27% of febrile patients presenting to these facilities had a parasitological diagnostic test performed. When diagnostic tests were performed and reported as negative for P. falciparum
over 35% of patients were still prescribed an antimalarial. Malaria parasite prevalence rates in the study districts range from 15.6% in Chipata and 18.2% in Chingola, two districts with meso- and hyperendemic malaria, to 40.4% in Samfya, a hyperendemic district.(17
) While these data derive from a survey that was carried out in the dry season in 2004, a more recent nationwide survey carried out in the late rainy season showed similar findings with malaria parasite prevalence rates ranging from 8.6% in Southern Province (where Kalomo District is located) to 37.5% in Luapula Province (Samfya District).(18
) Given the high specificity of the RDTs used in the study district health centers, the prevalence of malaria in children is not high enough to warrant routinely treating all those with negative malaria diagnostic tests.
Among patients who had no parasitological diagnostic tests performed, 42% were prescribed AL. Although slightly fewer patients with negative microscopy or RDT results were provided with AL in health facilities where this drug was available, AL was nevertheless used in more than a quarter of all patients with negative diagnostic tests including a substantial portion of febrile older children and adults.
RDTs have been proposed as a cost-effective approach to reducing the over-treatment of malaria(5
); however, under current practice in Zambia, their use will not limit the overuse of expensive new treatments. Assuming an estimated cost of US$0.5 per RDT against the recently reduced price per adult treatment course of AL of US$1 per course, for every 1000 febrile patients with negative RDT results, the cost savings would only be $0.33 per patient or $330 per 1000 patients if 27% of patients with negative test results still received AL treatment as suggested by our findings. Given the additional costs associated with training of health care workers in RDT use and interpretation, it does not appear that the way these diagnostics are currently used is cost-effective.
Although the national malaria guidelines in Zambia recommend the use of malaria microscopy whenever possible, they state that the “presence of signs and symptoms of disease with negative blood smear does not preclude the diagnosis of malaria”.(19
) Similar ambiguous recommendations are also provided in malaria training manuals.(20
) None of the training materials or national guidelines in Zambia provides specific instructions on how to respond to negative RDT results. Although patients with negative RDT results were less likely to receive antimalarial treatment than those with negative blood smears, this difference was not statistically significant, possibly because the small numbers of patients in these groups resulted in our not having sufficient power to detect a difference. A recent randomized trial that compared the use of malaria microscopy to RDT in Tanzania found that slightly more than half of patients with negative blood smears or negative RDT results were prescribed an antimalarial.(16
) In many countries in Africa, there continues to be a clinical dogma that regards blood smear-negative results as “suspected” malaria.(1
) Our study and the study by Reyburn et al
) suggest that this clinical dogma is being extended to RDT results as well. Since the malaria parasite prevalence in the study districts is likely to be less than 50% during much of the calendar year, the routine treatment of negative RDT or blood smear results is not warranted. In the absence of a paradigm shift away from treatment of patients with negative blood smears towards the appropriate interpretation of RDTs, with specific guidelines on how to investigate fevers if the rapid test is negative, this new diagnostic intervention is unlikely to improve clinical management or result in the anticipated cost-savings from the misuse of expensive ACT in Africa.
Given the widespread scaling up of ACT in sub-Saharan Africa for the management of uncomplicated malaria, there is a clear need to limit the inappropriate use of these expensive new combinations. Given the increasing body of evidence that a substantial proportion of febrile patients do not have malaria, especially in low to moderate transmission zones(16
), efforts need to be undertaken to educate health center staff on the rational use of ACTs. This will require strengthening the availability of malaria diagnostics and enhancing quality control measures so that health care providers will have confidence in the malaria test results. As currently structured in Zambia, the RDT training program needs to be restructured such that trainees are provided with clear instructions as to how to respond to a negative test result. Without taking these steps, we may rapidly be confronted with widespread resistance of P. falciparum
to ACT and the lifespan of these highly effective new therapies will be greatly reduced.