Performance of rapid diagnostic tests, microscopy, and qPCR for detection of parasites among community members with or without symptoms of malaria in villages with high levels of artemisinin partial resistance in North-western Tanzania
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Background
Despite the implementation of different control interventions, infections in the communities (among asymptomatic and symptomatic individuals) still play a crucial role in sustaining malaria transmission. This study evaluated the performance of rapid diagnostic tests (RDTs), microscopy, and quantitative PCR (qPCR) in detecting malaria parasites among community members in five villages of Kyerwa district, Kagera region, an area where artemisinin partial resistance (ART-R) has been recently confirmed.
Methods
A community cross-sectional survey of asymptomatic and symptomatic participants (n=4454) aged ≥6 months was conducted in July and August 2023. Malaria infections were detected using RDTs, microscopy, and qPCR (using 18S RNA gene). Performance of RDTs and microscopy was assessed by sensitivity, specificity, and predictive values, using qPCR as the reference method. Factors affecting the accuracy of these methods were explored using a multivariate logistic regression model.
Results
The prevalence of malaria infections was 44.4% (n = 1979/4454), 32.1% (n = 1431/4454), and 39.8% (n = 1771/4454) by RDTs, microscopy, and qPCR, respectively. The prevalence of P. malariae and P. ovale mono-infection by microscopy was 0.2% (n = 7/4454) and 0.3% (n = 12/4454), while by qPCR was 0.4% (n = 16/4454) and 0.5% (n = 24/4454), respectively. The geometric mean parasite densities (GMPDs) by microscopy were 642 (95% confidence intervals (CI) = 570 - 723), 126 (95% CI = 98 - 162), and 124 (95% CI = 82 - 160) asexual parasites/µL; while by qPCR, the GMPDs were 1180 (95% CI = 1032 - 1349), 44 (95% CI = 32 - 61), and 50 (95% CI = 29 - 89) parasites/µL for P. falciparum, P. ovale spp , and P. malariae , respectively. The sensitivity and specificity of RDTs were 94.0% (95% CI = 92.8% - 95.1%) and 87.5% (95% CI = 86.2% - 88.7%), respectively; whereas those of microscopy were 74.6% (95% CI = 72.5% - 76.6%) and 95.2% (95% CI = 94.3% - 96.0%), respectively. The sensitivity of RDTs, and microscopy was low at very low parasitaemia (<100 parasite/μL), but increased significantly with increasing parasitaemia, reaching ≥99.6% at >10000 parasites/μL (p<0.001).
Conclusion
Higher prevalence of malaria was detected and the performance of RDTs and qPCR were comparable, but microscopy had lower performance. Higher sensitivity by RDTs compared to microscopy, indicate that RDTs are effective for detection of malaria infections for routine case management and surveillance of malaria in this area with confirmed ART-R; and can be utilized in the ongoing plans to develop a response to ART-R.
