Evaluation of a dry format reagent alternative for CD4 T-cell enumeration for the FACSCount system: a report on a Moroccan-Canadian study.

BACKGROUND: Efforts to improve alternative CD4 T-cell counting methods are critical to accelerate the implementation of HIV antiretroviral therapy in resources limited regions. Substituting liquid format reagents to eliminate cold-chain transportation and refrigerated storage with dry format reagents contributes to higher efficiency supply management solution especially for laboratories at remote locations. ReaMetrix has developed dry format reagent kits compatible with the FACSCount system, a dedicated flow cytometer for T-cell subset enumeration widely used in resource limited settings. A dual site collaborative study was designed to compare T-cell subsets using both the new dry format ReaMetrix reagent and the original BD Biosciences liquid reagents. METHOD: A total of 167 HIV positive samples prepared with Rea T Count (ReaMetrix) and FACSCount (BD Biosciences) reagents were analyzed using FACSCount Systems. To compare both methods, Bland-Altman, Pollock, Scott % similarity and correlation coefficient statistical analysis was applied. Immuno-Trol served as an assay processing control and quality indicator of interlaboratory and intralaboratory variation. RESULTS: The mean bias and limits of agreement for CD4 T-cell measurements between Rea T Count and FACSCount reagents were -16 cells/microl (-4.6%) and -74 to +43, respectively. The correlation obtained was 0.988 with a similarity of 97.9%. Between laboratory variation data was very good with %CV below 10%. CONCLUSION: The introduction of dry reagents permits the elimination of cold-chain transportation and the on-site refrigerated storage without compromise to assay quality. The substitution of dry reagents facilitates easier supply management practice that will assure wider access to quality HIV treatment.

QASI, an international quality management system for CD4 T-cell enumeration focused to make a global difference.

BACKGROUND: A significant worldwide mobilization effort to treat people with HIV disease began in 2003. Most guidelines for initiating antiretroviral therapy require reliable and reproducible CD4 T-cell counting. Therefore, any effort that improves global availability of quality managed assessment schemes for CD4 T-cell enumeration is a positive achievement for the clinical management of AIDS on a worldwide scale. METHODS: The Canadian QASI-Quality Management System (QMS) has been in operation for over a decade. More recently, QMS has fine-tuned its strategy to optimize its global impact in the fight against the HIV/AIDS pandemic. Three modifications were implemented: (1) introduction of skills and knowledge transfer workshops pertaining to the initiation of national quality management programs for CD4 counting, (2) introduction of a road map to establish domestic EQAP for countries that are ready, and (3) introduction of a statistical analysis package which permits continuous monitoring of global impact of the QASI-QMS. RESULTS: Based on QASI-QMS distribution of specimens over four consecutive participation cycles, there was decreased interlaboratory variation for both low and medium CD4 T-cell levels. After three cycles of consecutive participation, there is an average of 38 and 26% error reduction reported for the mid and low CD4 levels, respectively. CONCLUSION: The program improvements mentioned earlier appear to have had a profound effect with regard to enhancing the performance of laboratories participating in the QASI-QMS. Specifically, there is a significant reduction in interlaboratory variability of CD4 T-cell counts resulting from continuous participation in the QASI-QMS.

Evaluation of stabilized blood cell products as candidate preparations for quality assessment programs for CD4 T-cell counting.

BACKGROUND: Exceptionally robust cell preparations are needed for quality assessment programs (QAPs) such as the International Program for Quality Assessment and Standardization for Immunological Measures (QASI) relevant to HIV/AIDS. A suitable product must withstand environmental stress related to transportation for a minimum of 6 days. The two objectives of this study are (1) to evaluate the performance of various commercial preparations with multicenter participation and (2) to evaluate the robustness of stabilized blood cell products. METHODS: Phase 1: The performance of stabilized blood cell products was evaluated in a multicenter QAP utilizing various staining procedures and flow cytometers. Absolute cell enumeration was achieved using single-platform T-cell subset methodology. Phase 2: The robustness of stabilized blood cell products was evaluated by monitoring T-cell subset values from samples stored at 4 degrees C, 22 degrees C, and 37 degrees C for up to 10 days. RESULTS: The largest interlaboratory variation in both absolute and relative T-cell values was 16% in samples with CD4 levels > or =400 cells per microliter and 21% in samples with CD4 levels <400 cells per microliter. Six preparations retained their phenotypic expression for 7 days at 4 degrees C and 22 degrees C. However, only two preparations remained stable for 4 days at 37 degrees C. CONCLUSION: Some stabilized cell preparations are more robust and therefore more suitable for quality assessment purposes.