ABSTRACT
A CD4 count External Quality Assessment (EQA) program is important for the clinical monitoring of persons infected with HIV/AIDS. The purpose of the present study was to evaluate the CD4 EQA performance program of the flow cytometer laboratories that perform routine CD4 counts for these patients in Thailand. Stabi-lized whole blood samples were sent to participating laboratories to determine the percentage and absolute counts of CD4+ T-lymphocytes using their routine procedures. The data were analyzed and reports sent to the participants within one month. Most participating laboratories produced results that were within two standard deviations (SD) of the mean, while the average inter-laboratory coefficients of variation were less than 8% for CD4+ T-lymphocytes. This program was found to improve the reliability of CD4+ T-lymphocyte determinations. This test is becoming in-creasingly important as Thailand and other Southeast Asian countries scale up their national programs that provide access to antiretroviral therapy for persons living with HIV/AIDS.
ABSTRACT
In Thailand, the cost of antiretrovirals has recently been reduced more than 10 fold. Likewise strategies for a cost reduction in laboratory monitoring are warranted. This study was designed to explore if the most expensive reagent in flow cytometry based CD4+ cell monitoring, the CD4+/CD8+ monoclonal antibodies, can be reduced without a loss of accuracy. Blood samples from 55 HIV seronegative (HIV-) and 76 HIV+ subjects were analyzed for %CD4+ and %CD8+ T cells using a two color monoclonal antibody panel (BD Biosciences, CA, USA) with 3 different amounts of the recommended reagents for staining: 1) standard, 2) half, and 3) one-fourth. A significant Spearman correlation of 0.987 was shown for the % CD4+ T cell test results for one half as well as one-fourth of the recommended amount compared to the standard staining according to the manufacturer's instruction (p < 0.0001). For the % CD8+ T cell test results, the correlation between the standard and the half or one-fourth reduced staining was 0.972 (p < 0.0001). Bland-Altman analysis showed no significant bias between the results from one half or one-fourth of the recommended amount versus the standard. The sensitivity and specificity of the two methods at the CD4+ T cell count cut-off of 200 cells/microl were 93% and 100%; and 96% and 99%, respectively. Our study indicates that a reduction of the reagents to half or one-fourth of the amount recommended by the manufacturer was still able to generate reliable results for CD4+ and CD8+ T cell counts. Such an approach will significantly reduce the cost of CD4+ monitoring for resource limited settings where a flow cytometer is available.