A-381 Laboratory-based Reflexive Algorithm for Identification of Falciparum and Non-Falciparum-Species and its Clinical Utility in the Diagnosis of Malaria in Southern Ghana

Abstract

Abstract Background Malaria presents a public health menace to millions of people in LMICs, killingmore than 600 000 people with the highest number in children living in sub-Saharan Africa.Laboratory testing provides the basis for >70% of clinical decisions, although their accessibilityand affordability are limited in LMICs and results in syndromic diagnosis and self-medication.The National Malaria Control Program guidelines specify that healthcare facilities perform RapidDiagnostic Testing (RDT) or microscopy for the diagnosis of malaria. This “one size fits all”approach has the unfortunate potential of resulting in a higher number of false positives and falsenegatives. Although Plasmodium falciparum is the predominant species in Ghana, emergingevidence suggests that non-falciparum species (P. vivax, P. ovale, P. malariae, and P. knowlesi)contribute to morbidity and mortality, and complicates the diagnosis and treatment for a subset ofpatients. The rationale for this study is the development of a reflexive, stratified diagnosticapproach that combines the use of RDTs and Microscopy/NAAT for the identification offalciparum and non-falciparum species in malaria endemic areas. Method Venous blood was collected from participants and five different RDTs on the Ghanaianmarket were used to screen the blood for the presence of malaria parasites along with microscopyand the LAMP method. The diagnostic performance of the RDTs was evaluated by utilizingmicroscopy as the gold standard. For microscopy, a volume of 6 µL and 2 µL of the blood sampleswere pipetted onto labeled frosted- end slides for the preparation of thick and thin blood films,respectively. Lastly, DNA was extracted from venous blood (QIAamp DNA Mini Kit, Qiagen,Germantown, MD, USA) and analyzed using a modified version of the Nested Malaria PCR assaythat can identify the five species of the Plasmodium parasite including P. knowlesi. Results Preliminary data from results from 71 participants showed an overall sensitivity of 90%for the identification of Plasmodium infection among all the RDTs examined in this investigation.The Wondfo® One Step Malaria HRP2/pLDH (P.f/Pan) test was the only RDT that passed theWHO recommended specificity of 90% when compared to microscopy. The WHO recommends aminimum sensitivity of 95%; however, none of the five RDTs utilized in this study met thisrequirement. Conclusion Although microscopy remains the gold standard for the identification of Plasmodiumspp for malaria diagnosis, it is becoming increasing popular for most healthcare facilities in LMICsto use RDTs for screening of the huge patient numbers that present with febrile illness. From ourpreliminary results, we have shown that positive cases by RDTRs are usually confirmed positiveby microscopy while most RDT negatives are false negatives by microscopy. Our combinatorialapproach with the molecular testing assay using LAMP increases the specificity of the testingprocess that guides treatment for malaria patients.