The impact of a CD4 external quality assessment programme for Southern Africa and Africa

Aggett, Hazel Margaret
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Background: The aim was to review the first twenty trials of the regional CD4 AFREQAS scheme. This scheme was implemented to raise awareness of the need for quality laboratory testing and to continually improve and maintain a high standard of CD4 enumeration used in support of treatment programmes. The overall performance from 2002 to 2006 (Trials 1-20) is reported. Methods: Commercial stabilised CD4 external quality assessment (EQA) material, both with normal and low CD4 values were shipped across 20 trials. Data was analysed for each trial, for each participant which included; the trimmed mean, standard deviation, the percent coefficient of variation, the residual, and the standard deviation index (SDI) values for both the CD4 absolute counts (CD4 abs counts) and CD4 lymphocyte percentages (CD4%Ly). Individual laboratory SDI values across 20 trials were analysed according to CD4 methods. The cumulative pooled SDI data across 20 trials of subgroups of users, using similar methods were analysed. The overall performance of Southern African networks and Grant supported networks were assessed. Results: Overall CD4 AFREQAS between-laboratory precision (trimmed %CV) was 11.9% and 10.8% for CD4 abs counts and CD4%Ly respectively. For the respective CD4 abs counts and CD4%Ly where normal value material was shipped, trimmed %CV of 10.9% and 8.1% were observed, and in low value shipments trimmed %CV of 14.2% and 17.0% were observed. The cumulative CD4 abs counts SDI analysis showed the best between-laboratory precision amongst BDS FACSCount™ and Panleucogating (PLG-CD4) users (both SD (SDI) =<1.2 and %CV of <9%). Single platform algorithm based systems (BDS TruCOUNT™ MultiSET™) and volumetric systems (Partec®) showed poorer between-laboratory precision (both SD (SDI) =>2 and %CV of >13%). These two systems had more outliers and no submission results than the BDS FACSCount™ and PLG-CD4 users. With respect to the African and Grant supported networks, the CD4 AFREQAS scheme has highlighted a number of factors that have contributed to poor performance which are lack of training and poor service delivery. Investment in additional technical training by the service providers and improved service delivery will improve the quality of CD4 testing in Africa. Conclusion: From the inception of CD4 AFREQAS, significant advances have been made in the quality control and monitoring of participating national and African laboratories offering CD4 testing. CD4 AFREQAS has provided a platform for improving the reproducibility of CD4 reporting both within and between laboratories in South Africa and Africa. With ongoing teaching through participant feedback evaluation, and dedicated training programmes, as well facilitating the use of standardised laboratory protocols necessary to contain costs, and maintain high standards of CD4 testing, there has been a huge impact on establishing excellent CD4 service delivery.
MSc (Med), Molecular Medicine and Haematology, Faculty of Health Sciences, University of the Witwatersrand, 2009