Performance Evaluation of RDT, Light Microscopy, and PET-PCR for Detecting P. Falciparum Malaria Infections in the 2018 Zambia National Malaria Indicator Survey

Abstract BackgroundZambia continues to advance on the path to elimination with significant reductions in malaria morbidity and mortality. Crucial components that have contributed to progress thus far and are necessary for achieving the national malaria elimination goals include properly identifying and treating all malaria cases through accurate diagnosis. This study sought to compare and assess the diagnostic performance of RDTs and LM with PET-PCR as the gold standard using 2018 MIS data across Zambia to better understand diagnostic accuracy metrics and how these vary across a transmission gradient. MethodsCross-sectional samples collected in a nationally representative survey from 7 provinces in Zambia were tested for the presence of malaria parasites by light microscopy (LM), rapid diagnostic test (RDT) and the gold standard PET-PCR. Diagnostic performance was assessed including sensitivity, specificity, negative- and positive-predictive values across a wide malaria transmission spectrum. Diagnostic accuracy metrics were measured, and statistically significant differences were calculated between test methods for different outcome variables. ResultsFrom the individuals included in the MIS, the overall prevalence of P. falciparum malaria was 32.9% by RDT, 19.4% by LM, and 23.2% by PET-PCR. Herein, we compared RDT and LM diagnostic performance against gold standard PET-PCR and found that LM had higher diagnostic accuracy than RDTs (91.3% vs 84.6% respectively) across the transmission spectrum in Zambia. However, we found that the performance of both diagnostics was significantly reduced in low parasitemia samples. Consistent with previous studies, RDT diagnostic accuracy was predominantly affected by a high rate of false positives.ConclusionWhile LM performance is overall superior to RDTs, the additional requirements for its implementation such as high-quality staining, microscopes, and additional manpower, means that its application will remain at the health facility level. In contrast, while RDTs overestimate prevalence as they have a higher false positive rate, their ability to be rapidly deployed makes them an excellent community level tool. Overall, we found that the performance of both diagnostics was acceptable, and their use should be continued.