Performance of the PointCare NOW System for CD4 Counting in HIV Patients Based on Five Independent Evaluations

Abstract

IntroductionPoint-of-care (POC) CD4 testing can improve access to treatment by enabling decentralization and reducing patient loss-to-follow-up. As new POC CD4 technologies become available, their performance should be assessed before widespread deployment. This study reports the findings of five independent evaluations of the PointCare NOW CD4 system.Materials/MethodsEvaluations were conducted in Southern Africa (Mozambique, South Africa) and North America (Canada, USA). 492 blood samples (55 from HIV-negative blood donors and 437 from HIV-infected patients, including 20 children aged between 12 and 59 months) were tested with both the PointCare NOW and reference flow cytometry instruments. Assessment of bias, precision and levels of clinical misclassification for absolute and percent CD4 count was conducted.ResultsPointCare NOW significantly overestimated CD4 absolute counts with a mean relative bias of +35.0%. Bias was greater in samples with CD4 counts below ≤350cells/µl (+51.3%) than in the CD4 >350cells/µl stratum (15.1%). Bias in CD4% had a similar trend with an overall relative mean bias of +25.6% and a larger bias for low CD4 stratum (+40.2%) than the higher CD4 stratum (+5.8%). Relative bias for CD4% in children was −6.8%. In terms of repeatability, PointCare NOW had a coefficient of variation of 11%. Using a threshold of 350cells/µl, only 47% of patients who qualified for antiretroviral therapy with reference CD4 testing, would have been eligible for treatment with PointCare NOW test results. This was 39% using a 200cells/µl threshold. Agreement with infant samples was higher, with 90% qualifying at a 25% eligibility threshold.ConclusionThe performance of the PointCare NOW instrument for absolute and percent CD4 enumeration was inadequate for HIV clinical management in adults. In children, the small sample size was not large enough to draw a conclusion. This study also highlights the importance of independent evaluation of new diagnostic technology platforms before deployment.

Analysis of Bias and ART Enrollment for a Point-of-Care CD4/CD4% Analyzer

“…In contrast with our 2011 study, an older 2009 study showed substantial bias for the PointCare NOW with central laboratory machines [14]. Our results suggest that improvements had been made in the PointCare NOW in the intervening time and should be noted.…”

“…Our study, where data was obtained in 2011, yielded systematic error, replicate precision, and enrollment classification results that were substantially better than those reported from a 2009 study [4] of the PointCare NOW machine. This suggested to us that improvements had occurred.…”

Compatibility of Stabilized Whole Blood Products with CD4 Technologies and Their Suitability for Quality Assessment Programs

“…SWBPs tested on the PointCare Now platform in the “patient” mode were not measurable for percentage or absolute CD4 counts [16], thus testing on this platform was terminated at this stage of the study.…”

HIV point-of-care diagnostics: meeting the special needs of sub-Saharan Africa

“…A peer-reviewed assessment of the Poincare NOW revealed low sensitivity; 53% and 61% of adult patients at the 350 and 200 cells/μL thresholds, respectively, were misclassified [34,46]. The CD4 POC PIMA analyzer (Alere, Inc.) evaluated in South Africa and in Zimbabwe, however, performed well compared to the standard protocol [33,35].…”