External Quality Assessment on CD4+ T-cell count

Back ground: CD4+ T-cell count External Quality Assessment program is important for the evaluation of performance of CD4 count laboratories. The aim was to assess the quality of CD4 count laboratory performance using in-house Proficiency Testing panels that perform routine CD4 counts in Addis Ababa, Ethiopia, 2013/14.Methods: Participating laboratories were 20, 23, and 25 in trials 1, 2, 3 respectively. In-house prepared fresh whole blood samples both with normal and low CD4 values were sent to participating laboratories. Percentage and absolute counts of CD4+ 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 both absolute counts and percentages of CD4+ lymphocytes (%CD4). Results: Most participating laboratories produced results that were within 2SD of the mean. Average inter-laboratory precision (trimmed %CV) was 10.87% and 5.14% for CD4 absolute counts and %CD4 respectively. For normal material, the trimmed mean %CV was 9.59% and 3.23% for CD4 absolute counts and %CD4 respectively.