Evaluation of the Performance of Two Diagnostic Assays in Malaria Diagnosis in Mashonaland East Province, Zimbabwe, 2010

Introduction: Following the 2008 WHO in-vitro malaria RDT product testing study results, Paracheck RDT’s sensitivity was revealed to significantly drop to 55% at low parasite densities. This raised concerns among health workers on its diagnostic capabilities and possible public health implications resulting from its continued use? We therefore evaluated the diagnostic performance of Paracheck and SD Bioline (a yet to be evaluated kit) RDTs under operational settings in areas of different endemicity. Methods: Using an analytic cross-sectional study design, finger prick blood samples from 422 clinically diagnosed patients selected from Mudzi (high malaria burden) and Murewa (low malaria burden) districts were each tested for malaria using Paracheck and SD Bioline RDTs and Giemsa stain microscopy as gold standard. Parasitemias were calculated using WHO standard protocols. Main outcomes were test efficiency; sensitivity; specificity; PVP and NPV. Re-sults: Of eligible 390 blood slides prepared, microscopy detected malaria parasites in 125 (32.1%) with P. falciparum being predominant species (100%). Compared with microscopy, both Paracheck and SD Bioline RDTs performed fairly equally well and above WHO targets in Mudzi (high malaria burden), while in Murewa (low malaria burden) Paracheck and SD Bioline RDTs had sensitivities of 86.7% [69.5 - 100.0] and 86.7% [86.7 - 100.0]; specificities of 97.2% [94.1 - 100.0] and 90.7% [85.3 - 96.2]; test efficiencies of 95.9% [92.4 - 99.4] and 90.2% [85.0 - 95.5]; PVPs of 73.3% and 45.2%; and NPVs of 98.8% and 98.7% respectively. Sensitivities for Paracheck and SD Bioline RDTs reduced from 99.2% [97.7 - 100.0] at parasitemias above 1000/μl each to 33.3% [0.0 - 71.1] and 50.0% [10.0 - 90.0] respectively at parasitemias below 1000/μl with variations not statistically significant. Conclusion: Paracheck RDT remains the MOHCC’s preferred diagnostic alternative in areas where good quality microscopy is not available in Zimbabwe. SD Bioline RDT provides another diagnostic alternative especially in areas of high malaria burden. However performance of both kits at parasitemias below 1000/μl needs further investigation.