Malaria parasite found to produce false negative tests in children

According to a recent study by the University of North Carolina (UNC) at Chapel Hill, a particular malaria parasite affecting children in Africa is evading rapid diagnostic tests (RDT), threatening malaria eradication efforts.

Most RDTs rely on the detection of histidine-rich protein 2 (HRP2), an antigen specific to the plasmodium falciparum malaria parasite. The researchers said approximately 1 in every 15 children in the Democratic Republic of the Congo infected with that parasite is also infected by a pfhrp2-deleted mutant, producing a false-negative result when an RDT is used.

“This is the first nationwide study to demonstrate the presence and estimate the prevalence of malaria caused by pfhrp2-deleted P. falciparum in asymptomatic children,” Jonathan Parr, lead author of the study and UNC researcher, said. “Because most rapid diagnostic tests in the DRC are HRP2-based, they will fail to detect these parasites. Their spread would represent a serious threat to malaria elimination efforts.”

Samples were collected from children under the age of five during a health survey from 2013-2015 in the Congo, a nation with one of the highest malaria rates in the world. The UNC researchers focused on 783 samples with opposing rapid diagnostic tests and polymerase chain reaction (PCR) results. PCR testing produced a positive result for malaria whereas RDTs did not.

“We identified 149 P. falciparum isolates with a deletion of the pfhrp2 gene, representing a country-wide prevalence of 6.4 percent,” Parr said. “This proved that pfhrp2-deleted P. falciparum is a common cause of rapid diagnostic test negative, but PCR positive malaria test results among asymptomatic children in the Democratic Republic of the Congo. Surveillance for these deletions is needed and alternatives to HRP2-specific rapid diagnostic tests may be necessary.”

The research team published their findings in the Journal of Infectious Diseases and discussed them in greater detail at the American Society of Tropical Medicine and Hygiene’s annual conference.