Strong Cross‐Reactivity of Anti– <i>Plasmodium falciparum</i> <scp>pLDH</scp> Monoclonal Antibodies With <i>Plasmodium malariae</i> <scp>pLDH</scp> in the Abbott Bioline Malaria Ag P.f/P.f/P.v Rapid Diagnostic Test

OBJECTIVES: This study aimed to describe the cross-reactivity of the Abbott Bioline Malaria Ag P.f/P.f/P.v rapid diagnostic test, designed to detect Plasmodium falciparum and P. vivax, with other Plasmodium species, based on the detection of parasite lactate dehydrogenase enzymes. METHODS: Blood samples from 40 patients with positive thick and thin blood smear results were analysed: 10 infected with P. falciparum, 10 with P. vivax, 15 with P. malariae and five with P. ovale. Parasitemia was quantified as parasites/μL of blood. All samples were tested using the Abbott Bioline Malaria Ag P.f/P.f/P.v RDT, and species identification was confirmed by nested PCR. To compare test line intensities and assess potential nonspecific reactions, images of the RDT lines were analysed using ImageJ software. For statistical analyses, PCR was considered the gold standard. Sensitivity, specificity and accuracy were calculated using MedCalc 2026. Fisher's exact test was applied using GraphPad/Quick Calcs to compare the specificity of the anti-Pf-pLDH antibodies, with a significance level of 0.05 (p < 0.05). RESULTS: The RDT accurately detected all P. falciparum and P. vivax samples. However, 12 of 14 P. malariae samples yielded positive results on the T2 line, intended to be specific for Pf-pLDH, as did four P. ovale isolates. The specificity of the anti-Pf-pLDH monoclonal antibodies against P. malariae was only 14.29% (p < 0.05). ImageJ analysis showed that the T2 line signal intensity in P. malariae-infected samples exceeded that observed in P. falciparum-infected samples. CONCLUSIONS: This study provides the first evidence of cross-reactivity of anti-Pf-pLDH monoclonal antibodies in the Abbott Bioline Malaria Ag P.f/P.f/P.v RDT with P. malariae and P. ovale isolates. Moreover, highlights the imperative need to validate alternative biomarkers and novel point-of-care platforms, to enhance the rapid and accurate diagnosis of malaria, ensure species-specific treatment and ultimately support effective malaria control and elimination strategies.