Survival analysis of diagnostic assays in Plasmodium falciparum malaria

Malaria Journal

Research

Melissa Phuong¹  Rachel Lau²  Filip Ralevski²  Andrea K. Boggild³ 

[1] Faculty of Health Sciences, McMaster University, Hamilton, Canada;Public Health Ontario Laboratories, Public Health Ontario, Toronto, Canada;Public Health Ontario Laboratories, Public Health Ontario, Toronto, Canada;Tropical Disease Unit, Division of Infectious Diseases, UHN-Toronto General Hospital, 200 Elizabeth Street, 13EN-218, M5G 2C4, Toronto, ON, Canada;Department of Medicine, University of Toronto, Toronto, Canada;

关键词: Plasmodium falciparum;    Malaria diagnosis;    PCR;    Rapid antigen detection test;   

DOI  :  10.1186/s12936-015-0882-1

 received in 2015-07-06, accepted in 2015-09-03,  发布年份 2015

来源: Springer

【 摘 要 】

BackgroundRapid diagnostic tests (RDT) and real-time PCR (qPCR) assays are sensitive for diagnosing malaria, but because they detect antigen and DNA, respectively, positivity may not reflect active infection. Performance characteristics of RDT and qPCR in Plasmodium falciparum positive specimens were evaluated over time to elucidate duration of positivity following conversion to microscopy negative.MethodsSpecimens from patients with at least one specimen that was positive for P. falciparum by microscopy, and at least one specimen that was negative for P. falciparum within a 1-month period were identified. Survival distributions of the diagnostic tests over time were compared. Performance characteristics for each test were calculated.ResultsNinety specimens were included, with 48 initially positive for P. falciparum, and 42 subsequently negative. Of 42 specimens that converted to microscopy-negative following an initial positive, 26 (61.9 %) and 41 (97.6 %) were positive by qPCR and RDT, respectively. Survival curves of microscopy versus qPCR, as well as microscopy vs RDT differed significantly (p = 0.0002 and p < 0.0001, respectively). Compared to microscopy, sensitivity of qPCR was 100.0 % (95 % CI 90.8–100.0 %), and that of RDT was 100.0 % (95 % CI 90.8–100.0 %).ConclusionsDue to slow clearance of circulating antigen and DNA from bloodstream, RDT and qPCR have low positive predictive value for clinically relevant asexual parasitaemia in post-treatment specimens. Thus, microscopy remains the only available malaria diagnostic that can reliably distinguish true asexual parasitaemia from prolonged clearance of antigen and nucleic acid in a convalescing patient.

【 授权许可】

CC BY   
© Phuong et al. 2015