Health & body · 2016
Were malaria parasites missing a diagnostic target found in two Ghanaian communities?
Yes. Researchers found Plasmodium falciparum parasites lacking 2 of pfhrp2 in samples from Accra and Cape Coast, though results varied by sample group and test method. of pfhrp2 can affect the accuracy of widely used -based rapid tests.
Details
Malaria rapid diagnostic tests (RDTs) are important for malaria management and control. In Ghana, PfHRP-2-based RDTs are the most widely used rapid tests for diagnosing malaria. Deletion of pfhrp2 in Plasmodium falciparum parasites affects the accuracy of these tests. Knowing the prevalence and distribution of parasites with this deletion is important for malaria control. The study aimed to identify and confirm the prevalence of pfhrp2-deleted P. falciparum circulating in different regions of Ghana.
Researchers used Chelex-100 to extract DNA from the membranes of used CareStart™ PfHRP-2 RDT kits and from dried blood blots on filter paper. They amplified exon 2 of the pfhrp2 and pfhrp3 genes using polymerase chain reaction (PCR), separated the products by agarose gel electrophoresis and visualized them under UV light.
Among PfHRP-2 RDT-positive samples, microscopy of blood smears detected parasites in 54/114 (47.4%) from Accra and 2/26 (7.7%) from Cape Coast. PCR detected parasites in 94/114 (82.5%) and 6/26 (23.1%) of the RDT-positive samples from Accra and Cape Coast, respectively. In Accra, pfhrp2 exon 2 was deleted in 18/54 (33.3%) of the microscopy-confirmed and 34/94 (36.2%) of the PCR-confirmed RDT-positive samples. In Cape Coast, no RDT sample confirmed to contain parasites by microscopy or PCR was negative on the pfhrp2 exon 2 PCR test.
In a survey of an additional 558 dried blood spot samples, 46/205 (22.4%) of PCR-positive samples from Accra and 44/110 (40%) from Cape Coast lacked pfhrp2 exon 2 and possibly the entire pfhrp2 gene.
The researchers concluded that many P. falciparum parasites lacking pfhrp2 exon 2 were present in two Ghanaian communities. They said continuous nationwide monitoring of the prevalence of pfhrp2-deleted parasites would be essential for malaria control. They also suggested that tests effective despite pfhrp2 deletion, such as the PfHRP-2/PfLDH combination RDT, could improve clinical malaria diagnosis in Ghana.
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