Field evaluation of PIMA point-of-care CD4 testing in Rakai, Uganda

Ronald M. Galiwango, Lawrence Lubyayi, Richard Musoke, Sarah Kalibbala, Martin Buwembo, Jjingo Kasule, David Serwadda, Ronald H. Gray, Steven J. Reynolds, Larry W. Chang

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Objective: To assess the accuracy of PIMA Point-of-Care (POC) CD4 testing in rural Rakai, Uganda. Methods: 903 HIV positive persons attending field clinics provided a venous blood sample assessed on site using PIMA analyzers per manufacturer's specifications. The venous samples were then run on FACSCalibur flow cytometry at a central facility. The Bland-Altman method was used to estimate mean bias and 95% limits of agreement (LOA). Sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) were calculated for a CD4 threshold of <350 and <500 cells/uL for antiretroviral eligibility. Results: There was a high correlation between PIMA and FACSCalibur CD4 counts (r = 0.943, p<0.001). Relative to FACSCalibur, the PIMA POC CD4 had negative mean bias of -34.6 cells/uL (95% LOA: -219.8 to 150.6) overall. The dispersion at CD4<350 cells/uL was 5.1 cells/uL (95% LOA: -126.6 to 136.8). For a threshold of CD4<350 cells/uL, PIMA venous blood had a sensitivity of 88.6% (95%CI 84.8-92.4%), specificity of 87.5% (95%CI 84.9-90.1%), NPV of 94.9% (95%CI 93.1-96.7%), and PPV of 74.4% (95%CI 69.6-79.2%). PIMA sensitivity and PPV significantly increased to 96.1% and 88.3% respectively with increased threshold of 500 cells/uL. Conclusions: Overall, PIMA POC CD4 counts demonstrated negative bias compared to FACSCalibur. PIMA POC sensitivity improved significantly at a higher CD4 threshold of 500 than a 350 cells/uL threshold.

Original languageEnglish (US)
Article numbere88928
JournalPloS one
Issue number3
StatePublished - Mar 10 2014

ASJC Scopus subject areas

  • General


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