BACKGROUND: CD4+ T-cell count External Quality Assessment
program is important for the evaluation of performance of CD4
count laboratories. The aim of this study was to assess the quality
of CD4count laboratory performance using in-house Proficiency
testing panels that perform routineCD4 counts in Addis Ababa,
METHODS: Participating laboratories were 20, 23 and 25 in trials
1, 2 and 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% and3.23% for CD4 absolute counts and %CD4,
respectively. For low material, the trimmed mean % CV was
12.15% and 7.05% for CD4 absolute counts and %CD4
respectively. BDFACSCountTM users showed the best accuracy
and precision as evidenced by longitudinal analysis.