Evaluation of point-of-care Alere Pima CD4 test for low CD4 cell counts test in Uganda

Advanced HIV Disease (AHD) remains a significant concern globally, particularly in resource-limited settings. The introduction of point-of-care (POC) CD4 testing, specifically the PIMA analyser, has emerged as a potential solution for managing AHD care. This study aimed to evaluate the performance of the PIMA analyser in identifying patients with CD4 counts ≤ 200 cells/µL, which is crucial for timely AHD diagnosis and management. A cross-sectional study was conducted at Mildmay Uganda between April and July 2015, involving 302 HIV-positive adult patients. CD4 counts were measured using both the PIMA analyser (with capillary blood) and FACSCalibur flow cytometry (with venous blood) as the gold standard. The study calculated sensitivity, specificity, positive and negative predictive values, and likelihood ratios for the PIMA analyser at the CD4 threshold of ≤ 200 cells/µL. The study included 110 participants (62.73% female, 37.27% male) with a median age of 39 years. At the ≤ 200 cells/µL threshold, the PIMA analyser demonstrated a sensitivity of 55.56% (95% CI 21.20-86.30%), specificity of 98.02% (95% CI 93.03-99.76%), positive predictive value of 71.43% (95% CI 36.01-91.74%), and negative predictive value of 96.12% (95% CI 92.26-98.09%). The positive and negative likelihood ratios were 28.06 (95% CI 6.31-124.66) and 0.45 (95% CI 0.22-0.94), respectively. Bland-Altman analysis showed a slight negative bias of -0.1636 (95% CI - 194.8-194.5) for the PIMA analyser compared to FACSCalibur. The study found lower sensitivity for the PIMA analyser at the ≤ 200 cells/µL threshold compared to previous studies, which reported sensitivities around 96%. However, the high specificity and negative predictive value suggest good performance in correctly identifying individuals above the threshold and ruling out low CD4 counts. The discrepancy in sensitivity warrants further investigation, considering factors such as sample size, population characteristics, operator training, and environmental conditions. Despite the lower sensitivity, the PIMA analyser's portability and rapid results still offers potential benefits for decentralized AHD care in resource-limited settings.