Accuracy and acceptability of VISITECT CD4 Advanced Disease compared to PIMA CD4

Abstract

CD4 testing is the first step of the advanced HIV disease (AHD) care package. The semi-quantitative VISITECT CD4 Advanced Disease (Accubio Limited, VISITECT) is increasingly used but has variable reported performance. We compared VISITECTs diagnostic accuracy and acceptability with PIMA CD4 (Abbott, PIMA) at point-of-care within the AHD care package. Mixed-methods study embedded in a community-based TB case-finding trial in South Africa. Following a VISITECT batch recall (April 2023), a sample of trial participants with HIV (PWH) received VISITECT and PIMA testing in parallel on one venous blood sample. Sensitivity, specificity and positive and negative predictive values (PPV, NPV) were calculated. We conducted in-depth-interviews with PWH, focus group discussions with nurses, and participant observations with nurse/PWH pairs. Among 609 included PWH, 76 (12.5%) were found to have ≤200 cells/µl on VISITECT versus 28 (4.8%) on PIMA. The sensitivity, specificity, PPV and NVP of VISITECT were 89.3% [95%CI 71.8-97.7%], 91.2% [95%CI 88.6-93.4%], 32.9% [95%CI 22.5-44.6%] and 99.4% [95%CI 98.4-99.9%] compared to PIMA, respectively. Three VISITECT results (0.05%) were false negative (CD4 counts: 16, 82, 175 cells/µl) and 51 (8.4%) false positive (median CD4 counts: 563, IQR: 382-739 cells/µl). PWH and public sector nurses believed that point-of-care CD4 tests improve access to CD4 counts. Study nurses preferred PIMA to VISITECT in terms of accuracy, duration, user-friendliness, and yielding a numeric CD4 result. Compared to PIMA, VISITECT had a good diagnostic accuracy but low PPV, and was less acceptable for study nurses. VISITECT’s role should be further evaluated.