Performance of rapid diagnostic tests, microscopy, and qPCR for detection of Plasmodium parasites among community members with or without symptoms of malaria in villages located in North-western Tanzania

BACKGROUND: Despite the implementation of different control interventions, Plasmodium parasite 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 Plasmodium parasites among community members in five villages of Kyerwa district, Kagera region in north-western Tanzania. METHODS: The study used samples and data collected during a community cross-sectional survey of asymptomatic and symptomatic participants (n = 4454) aged ≥ 6 months which was conducted in July and August 2023. Plasmodium parasites were detected using RDTs, microscopy, and qPCR (targeting 18S rRNA gene). The 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 determined using a multivariate logistic regression model. RESULTS: The prevalence of Plasmodium parasite infections among 4454 participants was 44.4%, 32.1%, and 39.8% by RDTs, microscopy, and qPCR, respectively. The prevalence of Plasmodium falciparum, Plasmodium malariae and Plasmodium ovale mono-infection by microscopy was 28.7%, 0.2%, and 0.3%, while by qPCR it was 35.3%, 0.4% and 0.5%, 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 for P. falciparum, P. ovale spp., and P. malariae, respectively. By qPCR, the GMPDs were 1180 (95% CI = 1032-1349) parasites/µL for P. falciparum, 44 (95% CI = 32-61) for P. ovale spp., and 50 (95% CI = 29-89) for P. malariae. 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 parasites/μL) but increased significantly with increasing parasitaemia, reaching ≥ 99.6% at > 10,000 parasites/μL (p < 0.001). CONCLUSION: High prevalence of Plasmodium parasites was detected, and the performance of RDTs and qPCR was comparable, but microscopy had lower performance. Higher sensitivity of RDTs compared to microscopy indicates that RDTs are effective for detection of infections caused by Plasmodium parasites in routine case management and surveillance in this area with confirmed artemisinin partial resistance (ART-R) and can be utilized in the ongoing plans to develop a response to ART-R.