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 isimportant for the evaluation of performance of CD4 count laboratories.
Objective: The purpose of the present study is to assess the quality of CD4 count laboratoryperformance 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 wereparticipated 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 toparticipating laboratories. The percentage and absolute counts of CD4+ T-lymphocytes weredone using their routine procedures. The data were analyzed using Microsoft Excel, sigma plotversion 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), theresidual, and the standard deviation index (SDI) values for both the absolute counts andpercentages of CD4+ lymphocytes (%CD4). Feedback was provided to each respectiveparticipant 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 CD4EQA 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, thetrimmed mean %CV (between-laboratory precision) was 12.15% and 7.05% for CD4 absolutecounts and %CD4 respectively. The percentage outlier rate of absolute CD4for all trials were 4.3% and 4.1% respectively.
Conclusion: CD4 EQA program using In-house PT panels was found to help facilities in earlidentifying their gaps with regard to their CD4 count performance. In-hoprepared PT panels was helpful in avoiding the challenges encountered during participation in external EQAproviders like the high cost, transportation problem, feedback delay, CD4 laboratory coverage. TM
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CD4 + T-Cell