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Published on: August 13, 2009
The Diagnostic Performance of the Visitect Advanced Disease Point-Of-Care CD4 Platform: A Pragmatic, Mixed-Methods,
Elizabeth Nalintya1, Preethiya Sekar2, Olive L Namakula1
1Infectious Diseases Institute, College of Health Sciences, Makerere University, Kampala, Uganda.
Background:
The Visitect CD4 Advanced Disease test (AccuBio, Alva, United Kingdom) is a rapid, semiquantitative assay that estimates CD4 results above or below 200 cells per microliter. We evaluated the performance of the Visitect CD4 assay in semiurban laboratories in Uganda.
Methods:
We performed a pragmatic laboratory validation of the Visitect CD4 platform in 4 routine HIV clinics in Uganda, nested within a cluster randomized trial evaluating an enhanced package of screening and treatment for persons with advanced HIV disease (NCT05085171). As part of the clinical trial, samples processed on the Visitect CD4 platform were confirmed using another CD4 testing method. We compared the diagnostic performance of the Visitect CD4 platform against the confirmatory method by evaluating the sensitivity, specificity, and positive and negative predictive values.
Results:
Of 1495 venous blood samples that were processed both by the Visitect CD4 test and another confirmatory CD4 platform at clinics in Kampala, Uganda, specificity was 81% [95% confidence interval (CI): 79% to 84%] and the positive predictive value was 69% (95% CI: 66% to 73%). There were no samples for which the Visitect test was >200 cells per microliter and the confirmatory test was ≤200 cells per microliter, resulting in a sensitivity of 100%. Among Visitect CD4 tests that were read as ≤200 cells per microliter with confirmatory results >200 cells per microliter, the median confirmatory CD4 result was 397 (IQR, 281-590) cells per microliter. Specificity varied by clinic ranging from 63% to 99%.
Conclusions:
Given variable specificity of the Visitect CD4 Advanced Disease platform, successful implementation will require consideration of clinic context and laboratory staffing.
