Laboratory-based performance evaluation of PIMA CD4Â + T-lymphocyte count point-of-care by lay-counselors in Kenya

BackgroundCD4 + T-lymphocyte count testing at the point-of-care (POC) may improve linkage to care of persons diagnosed with HIV-1 infection, but the accuracy of POC devices when operated by lay-counselors in the era of task-shifting is unknown. We examined the accuracy of Alere's Pima™ POC device on both capillary and venous blood when performed by lay-counselors and laboratory technicians.MethodsIn Phase I, we compared the perfomance of POC against FACSCalibur™ for 280 venous specimens by laboratory technicians. In Phase II we compared POC performance by lay-counselors versus laboratory technicians using 147 paired capillary and venous specimens, and compared these to FACSCalibur™. Statistical analyses included Bland-Altman analyses, concordance correlation coefficient, sensitivity, and specificity at treatment eligibility thresholds of 200, 350, and 500 cells/μl.ResultsPhase I: POC sensitivity and specificity were 93.0% and 84.1% at 500 cells/μl, respectively. Phase II: Good agreement was observed for venous POC results from both lay-counselors (concordance correlation coefficient (CCC) = 0.873, bias − 86.4 cells/μl) and laboratory technicians (CCC = 0.920, bias − 65.7 cells/μl). Capillary POC had good correlation: lay-counselors (CCC = 0.902, bias − 71.2 cells/μl), laboratory technicians (CCC = 0.918, bias − 63.0 cells/μl). Misclassification at the 500 cells/μl threshold for venous blood was 13.6% and 10.2% for lay-counselors and laboratory technicians and 12.2% for capillary blood in both groups. POC tended to under-classify the CD4 values with increasingly negative bias at higher CD4 values.ConclusionsPima™ results were comparable to FACSCalibur™ for both venous and capillary specimens when operated by lay-counselors. POC CD4 testing has the potential to improve linkage to HIV care without burdening laboratory technicians in resource-limited settings.