Comparison of Malaria Rapid Diagnostic Tests at Health Facilities and Community Level in Siaya County Kenya
Oriedo, Zebedee Ezekiel
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Malaria remains a major public health problem affecting an estimated 40% of the world’s population and resulting in more than 650,000 deaths worldwide every year. The emergence and rapid spread of parasite resistance to affordable, easy to use and widely available anti-malarial drugs such as chloroquine and sulfadoxine-pyrimethamine (SP) has prompted many countries in endemic areas to switch to the more effective artemisinin-based combination therapies (ACTs). To mitigate against the emergence of resistance and improve patient care, the World Health Organization (WHO) recommends parasitological confirmation by microscopy or Rapid Diagnostic Tests (RDTs) before treatment. Malaria diagnosis by microscopy has many challenges including need for electricity, well trained staff and high quality reagents which are often lacking in areas where malaria is endemic. In such areas RDTs provide an alternative diagnostic method since they do not require highly trained personnel and can be performed by the community health workers. However, there is limited information in the performance characteristics (sensitivity, specificity, positive and negative predictive values) of RDTs when performed in health facilities or in the community. In this study, the performance characteristics of SD Bioline malaria Ag P.f/ pan RDT in a cross-sectional survey was compared to that from four health facilities in an area of high malaria transmission of Siaya County, western Kenya. Expert microscopy was used as a gold standard and factors affecting their accuracy were explored using statistical analysis software (SAS) version 9.2. A total of 1223 children below five years; 604 from cross sectional survey and 619 attending four health facilities (HFs), were included in the study. Sensitivity and specificity of RDTs in the cross sectional survey were 96.2% and 48.1% respectively giving positive predictive value 49.9 and negative predictive value of 99%. The health facility study had a sensitivity of 99.5% and specificity of 54.4% with positive predictive value and negative predictive value of 84% and 98% respectively. The difference in RDT sensitivity and specificity between cross sectional survey and at HFs was statistically significant (p=0.001). The health facility prevalence of Plasmodium spp. infection was 70.60% by microscopy and 83.68% by RDT while in the cross sectional survey the prevalence was 34.93 % by microscopy and 67.38 % by RDT. The result of this study showed that there was a difference in the performance characteristics of RDTs carried out in health facilities and at the cross sectional survey. However, when the analysis of sensitivity is based on parasite density, the performance of RDTs in both health facility study and during cross sectional survey is comparable to expert microscopy. Deployment of RDTs, coupled with supportive supervision can potentially reduce misdiagnosis of malaria as a result of either over diagnosis or under-diagnosis.