Operational accuracy and comparative persistent antigenicity of HRP2 rapid diagnostic tests for Plasmodium falciparum malaria in a hyperendemic region of Uganda

• Published in: Malaria Journal
• Main Authors: Odong George W, Tibenderana James K, Kyabayinze Daniel J, Rwakimari John B, Counihan Helen
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2008
• Subjects: Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/1475-2875-7-221; https://doaj.org/article/14d1d6fcbb7f4688b036b5f0579cdca4

Abstract Background Parasite-based diagnosis of malaria by microscopy requires laboratory skills that are generally unavailable at peripheral health facilities. Rapid diagnostic tests (RDTs) require less expertise, but accuracy under operational conditions has not been fully evaluated in Uganda. There are also concerns about RDTs that use the antigen histidine-rich protein 2 (HRP2) to detect Plasmodium falciparum , because this antigen can persist after effective treatment, giving false positive test results in the absence of infection. An assessment of the accuracy of Malaria Pf™ immuno-chromatographic test (ICT) and description of persistent antigenicity of HRP2 RDTs was undertaken in a hyperendemic area of Uganda. Methods Using a cross-sectional design, a total of 357 febrile patients of all ages were tested using ICT, and compared to microscopy as the gold standard reference. Two independent RDT readings were used to assess accuracy and inter-observer reliability. With a longitudinal design to describe persistent antigenicity of ICT and Paracheck, 224 children aged 6–59 months were followed up at 7-day intervals until the HRP2 antigens where undetectable by the RDTs. Results Of the 357 patients tested during the cross-sectional component, 40% (139) had positive blood smears for asexual forms of P. falciparum . ICT had an overall sensitivity of 98%, a specificity of 72%, a negative predictive value (NPV) of 98% and a positive predictive value (PPV) of 69%. ICT showed a high inter-observer reliability under operational conditions, with 95% of readings having assigned the same results ( kappa statistics 0.921, p < 0.001). In children followed up after successful antimalaria treatment, the mean duration of persistent antigenicity was 32 days, and this duration varied significantly depending on pre-treatment parasitaemia. In patients with parasite density >50,000/μl, the mean duration of persistent antigenicity was 37 days compared to 26 days for parasitaemia less than 1,000/μl (log rank 21.9, p < ...