Diagnostic Performances of Non-Invasive Tests compared with Microscopy for Malaria Parasite Detection among Children in Nnewi, Southeast, Nigeria

Abstract

Current malaria diagnostic methods require blood collection, which may be associated with pain and the risk of transmitting blood-borne  pathogens, and often create poor compliance when repeated sampling is needed. This study determined the potential use of non- invasive methods (saliva and urine specimens) as alternative sample sources for the diagnosis of malaria infection using real-time polymerase Chain Reaction (qPCR) among children below five years in Nnewi, Anambra State, Nigeria. Biomarkers (18S rRNA) were  captured and concentrated from saliva and urine samples using a magnetic bead-based method. DNA recovered from the saliva and  urine samples was amplified using qPCR. The results revealed that, out of the 552 participants recruited in this study, the malaria prevalence based on blood microscopy was 55.1%. The prevalence of malaria among children based on the qPCR of saliva specimens was  343 (62.1%), out of which 301 (87.7%) were true positives (TP) and 42 (12.3%) were false positives (FP) when compared with microscopy.  Moreover, the prevalence of malaria among children based on qPCR of urine specimens was 269 (48.7%), of which 237 (88.1%) were true  positive (TP) and 32 (11.9%) were false positive (FP). When the qPCR method was compared to thick blood film-microscopy as the  reference standard, saliva qPCR had a sensitivity of 98.7%, specificity of 80.0%, positive predictive value (PPV) of 87.2%, and negative  predictive value (NPV) of 97.8%; urine qPCR had a sensitivity of 88.1%, specificity of 84.3%, PPV of 88.5%, and NPV of 83.8%. Saliva and  urine samples are therefore promising non-invasive approaches for malaria diagnosis, and their qPCR has a sensitivity comparable to   that of blood microscopy, despite the limitations of cost and turnaround time.