Assessment of two POC technologies for CD4 count in Morocco

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Abstract Background : In the era of “test and treat strategy”, CD4 testing remains an important tool for monitoring HIV-infected individuals. Since conventional methods of CD4 count measurement are costly and cumbersome, POC CD4 counting technique are more affordable and practical for countries with limited resources. Before introducing such methods in Morocco, we decided to assess their reliability. Methods : in this study 92 blood samples from HIV-infected patients, were tested by PIMA to generate absolute CD4 count and by FACSPresto to derive percentage and absolute CD4 count. Flow cytometry using FacsCalibur, was used as reference method for CD4 count comparison. Linear regression, Bland and Altman analysis were performed to assess correlation and agreement between POC methods and the reference method. In addition, sensibility and specificity, positive predictive value (PPV), negative predictive value (NPV) at 350 CD4 count threshold were also determined. Finally, because FACSPresto can also measure hemoglobin (Hb) concentration, 52 samples were used to compare FACSPresto against an automated hematology analyzer. Results : With PIMA technology, the coefficient of determination R 2 was 0.93. Regarding FACSPresto, R 2 was 0.93 and 0.96for absolute CD4 count and percentage CD4 count, respectively. Bland and Altman analysis displayed a mean bias of -32.3 cells/µl with a limit of agreement (LOA): -181.3 to116.8, for Pima. The mean bias for FACSPresto was -8.1 cells/µl with LOA:-158.2 to 142.0for absolute CD4 count and 0.2 with LOA:-3.8 to 4.3, for CD4 percentage. Moreover, with a threshold of 350 CD4 count, sensibility, specificity, PPV, NPV, were 98%, 87%, 89%, 86%, and 88%, 96%,93% and 92% for PIMA and FACSPresto, respectively. Finally, the hemoglobin measurement evaluation displayed an R 2 of 0.80 and a mean bias of-0.12 with a LOA between -1.75 and 1.51. Conclusion : When compared to the reference method, PIMA and FACSPresto have shown good performance, for CD4 counting. The introduction of such POC technology will speed up the uptake of patients in the continuum of HIV care, in our country.

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