Laboratory Evaluation of the VISITECT® Advanced Disease Semi-quantitative Point-of-care CD4 Test.

BACKGROUND: Advanced HIV disease (AHD; CD4 counts <200 cells/µL) remains common in many low- and middle-income settings. An instrument-free point-of-care test to rapidly identify patients with AHD would facilitate implementation of the World Health Organization (WHO) recommended package of care. We performed a laboratory-based validation study to evaluate the performance of the VISITECT® CD4 Advanced Disease assay in Botswana. SETTING: A laboratory validation study. METHODS: Venous blood samples from people living with HIV having baseline CD4 testing in Gaborone, Botswana, underwent routine testing using flow cytometry, followed by testing with the VISITECT® CD4 Advanced Disease assay by a laboratory scientist blinded to the flow cytometry result with a visual read to determine if the CD4 count was below 200 cells/µL. A second independent investigator conducted a visual read blinded to the results of both flow cytometry and the initial visual read. The sensitivity and specificity of the VISITECT® for detection of AHD were determined using flow cytometry as a reference standard, and inter-rater agreement in VISITECT® visual reads assessed. RESULTS: 1053 samples were included in the analysis. The VISITECT test correctly identified 112/119 samples as having a CD4 count <200 cells/µL, giving a sensitivity of 94.1% (95% confidence interval [CI] 88.3-97.6%) and specificity of 85.9% (95% CI 83.5-88.0%) compared to flow cytometry. Inter-rater agreement between the two independent readers was 97.5%, Kappa 0.92 (p<0.001). CONCLUSIONS: The VISITECT® CD4 Advanced Disease reliably identified individuals with low CD4 counts and could facilitate implementation of the WHO recommended package of interventions for AHD