IMPACT OF LOW PARASITAEMIA ON THE SENSITIVITY OF P. FALCIPARUM PFHRP2-BASED RAPID DIAGNOSTIC TEST IN BENUE STATE NIGERIA

Abstract

Most reported sensitivities of P. falciparum specific malaria rapid diagnostic tests (RDTs) do not account for the integrity of the PfHRP2 gene that produces the HRP2 antigen in P. falciparum infections. However, low sensitivity of RDTs could be due to the deletion of this gene. This study aimed to determine the sensitivity and specificity of P. falciparum specific HRP2-based RDT, investigate levels of parasitaemia and deletion of HRP2 gene in the parasites. A total of 272 children aged 0-14 years were diagnosed for malaria using CareStart Pf HRP2 malaria RDT, microscopy and nested species-specific malaria PCR.  The level of parasitaemia, malaria species composition, and pfHRP2 gene integrity of false negative malaria RDTs were also determined. The sensitivity of the RDT was 43.3%, 95%CI (37.7-50.3) versus microscopy, and 51.0%, 95%CI (40.5-61.3) versus PCR used as reference tests. Out of 47 false negative malaria RDTs, 100% were positive by P. falciparum species specific PCR, and had intact PfHRP2 gene. The geometric mean parasitaemia of the false negative RDT parasites was 178 parasites/µl of blood versus 939 parasites/µl of blood in true positive cases. Thus, the low sensitivity of the Pf HRP2 malaria RDT was not due to deletion of the pfHRP2 gene or the presence of non HPR2 producing malaria species. It was likely due to the low parasitaemia observed among the P. falciparum parasites.