Why malaria test kit results is sometimes wrong —Experts

Even as Nigeria works towards eliminating malaria, experts in a new study have warned against total reliance on malaria rapid diagnostic test (RDT) for malaria diagnosis, saying the kit for its quick diagnosis in some few cases can give false negative results.

In a study, researchers had evaluated RDTs performance in malaria testing and found it has limitations when there is the deletion of two genes in Plasmodium falciparum, the malaria-causing germ.

They had compared malaria tests results using RDTs with that using a microscope, the gold standard for malaria diagnosis, and found it actually gave false negative results.

The study, a part of a prospective cohort study, had pooled 66 samples comprising false negative (31) and true positive (35) and found about two of every 10 will give a false negative even when the disease is present.

The study, presented at the iResearch 2018 of the College of Medicine, University of Ibadan, was the first to report deletion of two genes in Plasmodium falciparum, the malaria-causing germ, in Nigeria.

It was part of a prospective cohort study evaluating the consequences of restricting artemisinin-based combination therapy (ACT), the recommended medicine for the treatment of P. falciparum malaria in children South West, Nigeria

The study, which involved Funwei Roland David; Christian N, Bolaji; Falade Catherine; Velavan P and Olusola O, said if those genes are deleted in any Plasmodium, then the RDT will not pick malaria.

It said: “due to such a false malaria test result, the person will deny ACT, the antimalarial drug based on WHO recommendation that only those that test positive for malaria should be treated.”

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The researcher said a larger study to the distribution of Plasmodium falciparum with gene deletion indifferent geopolitical areas is therefore required.

Mr Roland Funwei, speaking on the sidelines of the workshop, said “It is a major challenge. Peru and recently Eritrea had a high percentage of gene deletion and so a high percentage of false negatives. In that case, they had withdrawn the use of RDT and advise the use of alternative methods of malaria testing.”

Professor Catherine Falade said “what has worried us as clinicians are the false negatives, not the false positives. Malaria is so treatable and if somebody has malaria and because RDT missed it and it is not treated, it can progress, get worse and become cerebral malaria and that was part of what informed this study.”

Even though the distribution of Plasmodium falciparum with gene deletion is low, she said, the finding is crucial to Nigeria’s malaria eradicating programme and the development of an improved malaria diagnostic test.

She added: “So we need a further refinement of the RDTs. Of course, when malaria parasite density is low, malaria rapid diagnostic test (RDT) will not detect malaria even when there is no gene deletion in Plasmodium falciparum.”