A validation study of microscopy versus quantitative PCR for measuring Plasmodium falciparum parasitemia

• Published in: Tropical Medicine and Health
• Main Authors: Emma Ballard, Claire Y. T. Wang, Tran Tinh Hien, Nguyen Thanh Tong, Louise Marquart, Zuleima Pava, Joel Tarning, Peter O’Rourke, James S. McCarthy
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2019
• Subjects: Microscopy; qPCR; Plasmodium falciparum; Validation; Arctic medicine. Tropical medicine; RC955-962; Arctic
• Online Access: https://doi.org/10.1186/s41182-019-0176-3; https://doaj.org/article/4afeeb3dcaf24a6c990582f9bc2838ae

Abstract Microscopy and 18S qPCR are the most common and field-friendly methods for quantifying malaria parasite density, and it is important that these methods can be interpreted as giving equivalent results. We compared results of quantitative measurement of Plasmodium falciparum parasitemia by microscopy and by 18S qPCR in a phase 2a study. Microscopy positive samples (n = 355; median 810 parasites/μL [IQR 40–10,471]) showed close agreement with 18S qPCR in mean log10/mL transformed parasitemia values by paired t test (difference 0.04, 95%CI − 0.01–0.10, p = 0.088). Excellent intraclass correlation (0.97) and no evidence of systematic or proportional differences by Passing–Bablok regression were observed. 18S qPCR appears to give equivalent parasitemia values to microscopy, which indicates 18S qPCR is an appropriate alternative method to quantify parasitemia in clinical trials.