External Quality Assessment on CD4+ T-Cell Count Using in-House Proficiency Testing Panels for CD4 Count Laboratories in Addis Ababa, Ethiopia

Abstract

BACKGROUND: CD4+ T-cell count External Quality Assessmentprogram is important for the evaluation of performance of CD4count laboratories. The aim of this study was to assess the qualityof CD4count laboratory performance using in-house Proficiencytesting panels that perform routineCD4 counts in Addis Ababa,Ethiopia, 2013/14.

METHODS: Participating laboratories were 20, 23 and 25 in trials1, 2 and 3, respectively. In-house prepared fresh whole bloodsamples both with “normal” and “low” CD4 values were sent toparticipating laboratories. Percentage and absolute counts ofCD4+ T-lymphocytes were done using their routine procedures.Data were analyzed for each trial including trimmed mean,standard deviation (SD), percent coefficient of variation (%CV),residual, and standard deviation index (SDI) values for bothabsolute counts and percentages of CD4+ lymphocytes (%CD4).RESULTS: Most participating laboratories produced results thatwere within 2SD of the mean. Average inter-laboratory precision(trimmed %CV) was 10.87% and 5.14% for CD4 absolute countsand %CD4, respectively. For normal material, the trimmed mean%CV was 9.59% and3.23% for CD4 absolute counts and %CD4,respectively. For low material, the trimmed mean % CV was12.15% and 7.05% for CD4 absolute counts and %CD4respectively. BDFACSCountTM users showed the best accuracyand precision as evidenced by longitudinal analysis.
CONCLUSION: This study was found to help facilities in earlyidentifying their gaps with regard to their CD4 count performanceand in avoiding the challenges encountered during participationin external EQA providers like the high cost, transportationproblem, feedback delay and CD4laboratory coverage.