Rapid diagnostic tests for malaria: past, present and future

Abstract

Prompt and accurate diagnosis of malaria is part of an effective disease management (1) , because if not treated malaria can quickly become life-threatening, whereas false positives increase treatment costs and drug-induced resistance, giving a wrong idea of therapeutic efficacy. Since the symptoms of malaria are nonspecific, the observation of clinical features alone might not be enough and should be confirmed with a parasitological analysis. Microscopic examination of Giemsa-stained thin and/or thick blood smears remains the conventional approach for diagnosis (2). The sensitivity of this relatively inexpensive method is excellent, allowing the detection of as few as 5 parasites per µL of blood, and permitting also the determination of the infecting species and of the developmental stage of circulating parasites. In addition, smears provide a permanent record for quality assessment of the diagnosis. However, microscopy requires considerable expertise learned through extended training, the procedure is labor-intensive and time-consuming, and the variability in stains and in techniques used to collect and process blood affects slide interpretation (3). Finally, routine clinical microscopy cannot reliably detect very low parasitemias (<5 parasites/µL) or sequestered parasites, and mixed infections are often missed, especially when Plasmodium malariae and Plasmodium ovale are present, as their densities are often low relative to Plasmodium falciparum (