Abstract
False-negative results for Plasmodium falciparum histidine-rich protein (HRP) 2–based rapid diagnostic tests (RDTs) are increasing in Eritrea. We investigated HRP gene 2/3 (pfhrp2/pfhrp3) status in 50 infected patients at 2 hospitals. We showed that 80.8% (21/26) of patients at Ghindae Hospital and 41.7% (10/24) at Massawa Hospital were infected with pfhrp2-negative parasites and 92.3% (24/26) of patients at Ghindae Hospital and 70.8% (17/24) at Massawa Hospital were infected with pfhrp3-negative parasites. Parasite densities between pfhrp2-positive and pfhrp2-negative patients were comparable. All pfhrp2-negative samples had no detectable HRP2/3 antigen and showed negative results for HRP2-based RDTs. pfhrp2-negative parasites were genetically less diverse and formed 2 clusters with no close relationships to parasites from Peru. These parasites probably emerged independently by selection in Eritrea. High prevalence of pfhrp2-negative parasites caused a high rate of false-negative results for RDTs. Determining prevalence of pfhrp2-negative parasites is urgently needed in neighboring countries to assist case management policies.
Highlights
False-negative results for Plasmodium falciparum histidine-rich protein (HRP) 2–based rapid diagnostic tests (RDTs) are increasing in Eritrea
We investigated P. falciparum lacking pfhrp2 and pfhrp3 in Eritrea to determine whether pfhrp2/pfhrp3 deletions were a cause of false-negative results for histidine-rich protein 2 (HRP2)-based RDTs and to describe origins of parasites
Since malaria RDTs became available in the 1990s, growth in the number of tests, manufacturers, and volumes sold has been exponential [25,26]
Summary
False-negative results for Plasmodium falciparum histidine-rich protein (HRP) 2–based rapid diagnostic tests (RDTs) are increasing in Eritrea. All pfhrp2negative samples had no detectable HRP2/3 antigen and showed negative results for HRP2-based RDTs. pfhrp2negative parasites were genetically less diverse and formed 2 clusters with no close relationships to parasites from Peru. The RDTs involved were from 10 lots that had passed testing at a WHO–Foundation for Innovative New Diagnostics lot-testing laboratory To address this issue, the Ministry of Health (MOH) conducted exploratory investigations at 12 health facilities located in 4 regions of Eritrea and used different brands of RDTs. Results showed an overall falsenegative result rate of 80% (41/50) for microscopically confirmed cases of P. falciparum malaria [6]. On the basis of these findings, the MOH recalled the RDTs and investigated P. falciparum–specific parasite factors, such as presence of P. falciparum lacking HRP2, as a primary cause
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