Direct Comparison of Standard and Ultrasensitive PCR for the Detection of Plasmodium falciparum from Dried Blood Spots in Bagamoyo, Tanzania

Ultrasensitive PCR used in low-transmission malaria-endemic settings has revealed a much higher burden of asymptomatic infections than that detected by rapid diagnostic tests (RDTs) or standard PCR, but there is limited evidence as to whether this is the case in higher transmission settings. Using dried blood spots (DBS) collected among 319 schoolchildren in Bagamoyo, Tanzania, we found good correlation (Pearson's R = 0.995) between Plasmodium falciparum parasite densities detected by a DNA-based 18s rRNA real-time PCR (qPCR) and an RNA-based ultrasensitive reverse transcriptase (RT)-PCR (usPCR) for the same target. Whereas prevalence by usPCR was higher than that found by qPCR (37% versus 32%), the proportion of additionally detected low-density infections (median parasite density < 0.050 parasites/pL) represented an incremental increase. It remains unclear to what extent these low-density infections may contribute to the infectious reservoir in different malaria transmission settings.

Automated summary

Ultrasensitive PCR has shown a higher burden of asymptomatic malaria infections compared to RDTs or standard PCR in low-transmission endemic areas, with potential implications for the infectious reservoir. A study in Tanzania found good correlation between DNA-based qPCR and RNA-based usPCR in detecting Plasmodium falciparum parasite densities, indicating an incremental increase in low-density infections. The extent to which these low-density infections contribute to the infectious reservoir in different malaria transmission settings remains unclear.