Laboratory-based performance evaluation of PIMA CD4+ T-lymphocyte count point-of-care by lay-counselors in Kenya

J Immunol Methods. 2017 Sep;448:44-50. doi: 10.1016/j.jim.2017.05.006. Epub 2017 May 18.


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 resource-limited settings.

Keywords: Alere PIMA; Point of care CD4 evaluation.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

  • CD4 Lymphocyte Count / instrumentation*
  • CD4 Lymphocyte Count / methods
  • Clinical Laboratory Techniques*
  • Community Health Workers*
  • Counselors*
  • Diagnostic Errors
  • Equipment Design
  • HIV Infections / blood
  • HIV Infections / diagnosis*
  • HIV Infections / immunology
  • HIV Infections / virology
  • HIV-1 / immunology*
  • Humans
  • Kenya
  • Observer Variation
  • Point-of-Care Systems*
  • Point-of-Care Testing*
  • Predictive Value of Tests
  • Reproducibility of Results