Efficacy of Histochemical Staining Techniques in the Detection of Plasmodium falciparum Histidine-Rich Proteins in Blood of Children with Malaria

Objective: Falciparum malaria predominates in sub-Saharan Africa and children below five years are the most vulnerable. Giemsa-stained microscopy is the gold standard in malaria diagnosis. Diagnosis with rapid diagnostic test (RDT) kit is also common and over 80% of available malaria RDT kits is Plasmodium falciparum histidine-rich protein 2-based (Pfhrp2). However, these histidine-rich protein 2-based kits have been observed to give false positive and negative results due to persistent antigenemia and low parasitaemia respectively. Thus, the methods of Pauly, Perls, and Means & Feeney were adopted to explore the advantage of using microscopy for specific detection of these histidine-rich proteins and their usefulness in detecting low parasitemia in children. Methods: Children aged 0-5 years (n=200) visiting three hospitals and private laboratories in Calabar were recruited. Whole blood samples were tested with CareStart Malaria HRP2-based kit, and blood films were made and stained with Giemsa, Pauly, Perls and Means & Feeney for microscopy. Results: The sensitivity and specificity were Giemsa (56.4%, 79.8%), Means & Feeney (52.5%, 77.8%), Perls (47.5%, 85.9), Pauly (45.5%, 86.9%), and RDT (23.8%, 96%). Pauly method had the highest area under the curve of 0.830 while RDT method had the lowest of 0.661. Among the positive cases low parasitemia detected by the histochemical methods was Perls 36 (75%), Pauly 32 (69.6%), and Means & Feeney 34 (64.2%), and for Giemsa method 40 (70.2%). Conclusion: Pauly method was the most accurate. All three methods were sensitive in detecting low parasitemia. These diagnostic methods are useful in malaria diagnosis in this endemic population. J Microbiol Infect Dis 2018; 8(2):55-60