Analysis of bias and ART enrollment for a point-of-care CD4/CD4% analyzer

Abstract

Point-of-care technologies are a cornerstone for effective HIV care of patients in resource poor settings. They greatly reduce loss to follow up as the patients receive their results immediately and obtain appropriate treatment and other care. There are 593,000 people in urgent need of antiretroviral therapy in Zimbabwe for whom point-of-care technology may be a benefit. The PointCare NOW device was evaluated in order to assess systematic errors between it and conventional flow cytometry and haematology devices, such as the Becton Dickinson FACS Calibur Single Platform and the Sysmex XT-1800i. There being no calibration method for CD4 count on any platform, large systematic errors could affect therapy enrollment decisions. Specimens were collected from 104 patients from the Harare Central Hospital Opportunistic Infection clinic by venipuncture using EDTA tubes. Three samples were automatically excluded as unsuitable for analysis by the PointCare NOW internal control software flag system; for a rejection rate of 2.9%. No other samples were excluded. Each device performed within manufacturer's replicate precision specifications for all parameters. There was a small but statistically insignificant difference in mean absolute CD4 cell count (+8.6 cells/ μl), mean CD4% (+0.76%) and mean total lymphocyte count (+0.054×103 cells/μl) between the PointCare NOW and the central laboratory systems. There was a small but statistically significant difference in mean total white cell count (+0.28×103 cells/μl) and mean total haemoglobin (-0.74g/dl) measurements and Sysmex XT1800i. We compare two methods for qualifying patients for therapy and show that there was no statistically significant difference between PointCare NOW and FACSCalibur qualifications for either method. One method uses a conventional sharp cut-off and the other uses a newer idea based on patient variability. Our results indicate that the systematic errors determined in our study would not produce disparity in therapy enrollment action taken for a patient receiving results from a PointCare NOW and a FACSCalibur. Our study was completed in 2011 and when compared to other studies carried out in 2009, it suggests that there have been improvements in the PointCare NOW systematic error performance. © 2013 Gumbo P, et al.