Diagnostic performance of an ultrasensitive HRP2-based malaria rapid diagnostic test kit used in surveys of afebrile people living in Southern Ghana

Abstract

Background: The Alere™ Malaria Ag P.f Ultra-sensitive RDT (UsmRDT) kit is an HRP2-based malaria rapid diagnostic test (RDT) with enhanced sensitivity relative to the SD Bioline Malaria Ag P.f RDT (mRDT) kit. However, the diagnostic performance of the UsmRDT kit has not been evaluated in Ghana.

Methods: A total of 740 afebrile participants aged between 3 and 88 years old were recruited from the Central and Greater Accra Regions of Ghana during the off-peak malaria season. Axillary body temperature was measured, and a volume of 1 ml venous blood was drawn from each participant. Prior to separating the blood into plasma and packed cell pellets via centrifugation, the blood was spotted onto one UsmRDT and one mRDT kit and also used to prepare thick and thin blood smears as well as filter paper blood spots. Plasmodium falciparum specific polymerase chain reaction (PCR) was performed on gDNA extracted from 100 µl of the whole blood.

Results: The overall positivity rate for microscopy, PCR, UsmRDT and mRDT kit were 20.4%, 40.8%, 31.3% and 30.8%, respectively. Overall, the UsmRDT identified 9.3% (28/302) more PCR positive samples than the mRDT kits. All samples that were negative by the UsmRDT kit were also negative by the mRDT kit. Overall, the sensitivity and specificity of the UsmRDT was 73% (221/302) and 89% (388/436), respectively, while that for the mRDT kit was 58% and 90%, respectively.

Conclusion: Although the UsmRDT kit was not as sensitive as PCR at detecting asymptomatic P. falciparum carriage, it correctly identified P. falciparum in 9.3% of the study participants that were not captured by the mRDT kit. In malaria endemic settings, the UsmRDT would provide an added advantage by identifying more asymptomatic P. falciparum carriers than the mRDT kit for targeted treatment interventions.

Keywords: Asymptomatic; Sensitivity; Specificity; Ultrasensitive RDT.

Fig. 1

A map of Ghana highlighting the study sites. The map was created by Mr. Richard Adade, GIS & Remote Sensing Unit, Department of Fisheries using shapefiles from the Survey Department of the Ghana Statistical Services and ArcMap GIS v10.5

Fig. 2

Prevalence of asymptomatic individuals. a Age categorized prevalence of P. falciparum in Obom and Simiw by the different diagnostic methods. b Prevalence of P. falciparum prevalence in pregnant women from Ewim and non-pregnant women of the same age group from Simiw and Obom (combined) by the different diagnostic tests. PCR: P. falciparum species PCR; micro: microscopy; UsmRDT: ultra-sensitive Alere™ Malaria Ag P.f RDT kit and mRDT, SD Bioline Malaria Ag P.f RDT kit

Fig. 3

Detection of P. falciparum by different diagnostic methods. All samples were grouped into sets belonging to PCR, UsmRDT (ultra-sensitive Alere™ Malaria Ag P.f RDT kit) and mRDT (SD Bioline Malaria Ag P.f RDT kit positive samples)