Résumé
Background
Absolute CD4+ T-lymphocyte counts are used in the initiation and monitoring of antiretroviral therapy in HIV-infected patients: with the increase number of HIV infected patient and the reduce number of heath care system in rural zones, HIV monitoring in resource-constrained settings demands affordable and reliable CD4+ T lymphocytes enumeration methods. We evaluated a simple PIMA POC which is a dedicated system for enumeration that uses immunomagnetic and immunofluorescent technologies. The instrument was designed to be a low-cost, yet reliable and robust one. In this study, we assessed the correlation between most representative flow cytometry instruments present in Cameroon instead of CyFlow from PARTEC, FACSCount, and FACSCalibur both from Becton Dickinson.
Methods
CD4 surface markers on lymphocytes was measured on samples collected in EDTA tubes from 268 patients aged from 1 to 65 years old in three different health care structures. HIV infected patients are coming from CIRCB, Day Hospital of Hopital Central de Yaounde (HCY) and Hopital General de Yaounde (HGY). After inform consent, samples were collected and 101 samples were tested with the FACSCalibur, 60 samples were tested with the CyFlow and 107 samples were tested with the FACSCount flow cytometers. All these samples were tested by different technician with PIMA POC present in all these health care structures and the correlation and agreement were analyzed using linear regression and Bland–Altman analysis.
Results
The PIMA POC system has excellent precision, accuracy and linearity for CD4+ T lymphocytes enumeration. Good correlations were obtained between the PIMA POC system and other single platform methods. Bland–Altman plots showed interchangeability between the three machines. Absolute CD4+ T-lymphocyte values obtained from the PIMA system correlated well with Cyflow, FACSCount, and FACSCalibur method (r2 varies from 0.88 to 0.968,
P
< 0.0001). The comparison between values obtained from PIMA with CYFLOW, FACSCount, and FACSCalibur give
P
= 0.17,
P
= 0.5 and
P
= 0.6 respectively meaning that there is not significant differences between values obtained with PIMA and other flow machines.
Conclusion
This POC PIMA system is a simple and reliable system for enumeration of absolute CD4+ T-lymphocytes. Having one PIMA system easy to use, should reduce the cost and thus increase access to CD4 testing for HIV infected patients in resource-constrained countries. POC CD4 may also alleviate testing burdens at traditional central CD4 laboratories, hence improving test access in both rural and urban environments. This will reduce also the loss of follow up.