External Quality Assessment on CD4 + T-Cell count using In-house Proficiency Testing Panels for CD4 count Laboratories in Addis Ababa, Ethiopia.
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Date
2013-03
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Addis Abeba University
Abstract
Back ground: A CD4+ T-cell count External Quality Assessment (EQA) program is
important for the evaluation of performance of CD4 count laboratories.
Objective: The purpose of the present study is to assess the quality of CD4 count laboratory
performance using in-house Proficiency Testing (PT) panels that perform routine CD4 counts in
Addis Ababa, Ethiopia.
Methods: Voluntary sampling technique was employed and 20, 23, and 25 laboratories were
participated in trials 1, 2, 3 respectively. In-house prepared fresh whole blood samples both with
68 “normal” and 68 “low” CD4 count materials were sent according to WHO guidelines to
participating laboratories. The percentage and absolute counts of CD4+ T-lymphocytes were
done using their routine procedures. The data were analyzed using Microsoft Excel
, sigma plot
version 12.3, and Graph Pad® Prism version 5 for each trial, for each participant which included;
the trimmed mean, standard deviation (SD), the percent coefficient of variation (%CV), the
residual, and the standard deviation index (SDI) values for both the absolute counts and
percentages of CD4+ lymphocytes (%CD4). Feedback was provided to each respective
participant within one month of result submission in each trial.
Results: Most participating laboratories produced results that were within 2SD of the mean
(Mean ± 2SD). The average inter-laboratory precision (trimmed %CV) was 10.87% and 5.14%
for CD4 absolute counts and CD4% of Lymphocytes respectively. For the normal level CD4
EQA material, the trimmed mean %CV (between-laboratory precision) was 9.59% and 3.23%
for CD4 absolute counts and %CD4 respectively. For the low level CD4 EQA material, the
trimmed mean %CV (between-laboratory precision) was 12.15% and 7.05% for CD4 absolute
counts and %CD4 respectively. The percentage outlier rate of absolute CD4+ counts and % CD4
for all trials were 4.3% and 4.1% respectively.
Conclusion: CD4 EQA program using In-house PT panels was found to help facilities in early
identifying their gaps with regard to their CD4 count performance. In-house prepared PT panels
was helpful in avoiding the challenges encountered during participation in external EQA
providers like the high cost, transportation problem, feedback delay, CD4 laboratory coverage.
TM
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Keywords
CD4 + T-Cell