Abstract:
Background: CD4+ 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.
Methods: In 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 500cells/μl.
Results: Phase I: POC sensitivity and specificity were 93.0% and 84.1% at 500cells/μl,
respectively. Phase II: Good agreement was observed for venous POC results from both
lay-counselors (concordance correlation coefficient (CCC)=0.873, bias -86.4cells/μl) and
laboratory technicians (CCC=0.920, bias -65.7cells/μl). Capillary POC had good
correlation: lay-counselors (CCC=0.902, bias -71.2cells/μl), laboratory technicians
(CCC=0.918, bias -63.0cells/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.
Conclusions: Pima™ 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 resourcelimited settings.