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. 2016 Jul 7;11(7):e0157546.
doi: 10.1371/journal.pone.0157546. eCollection 2016.

Evaluation of the FACSPresto, a New Point of Care Device for the Enumeration of CD4% and Absolute CD4+ T Cell Counts in HIV Infection

Azure Tariro Makadzange  1   2 , Carola Bogezi  2 , Kathryn Boyd  2 , Anesu Gumbo  2 , Dorinda Mukura  3 , Allen Matubu  3 , Chiratidzo Ellen Ndhlovu  2
Affiliations

Evaluation of the FACSPresto, a New Point of Care Device for the Enumeration of CD4% and Absolute CD4+ T Cell Counts in HIV Infection

Azure Tariro Makadzange et al. PLoS One. .

Abstract

Introduction: Enumeration of CD4+ T lymphocytes is important for pre-ART disease staging and screening for opportunistic infections, however access to CD4 testing in resource limited settings is poor. Point of care (POC) technologies can facilitate improved access to CD4 testing. We evaluated the analytical performance of a novel POC device the FACSPresto compared to the FACSCalibur as a reference standard and to the PIMA, a POC device in widespread use in sub-Saharan Africa.

Method: Specimens were obtained from 253 HIV infected adults. Venous blood samples were analyzed on the FACSPresto and the FACSCalibur, in a subset of 41 samples additional analysis was done on the PIMA.

Results: The absolute CD4 count results obtained on the FACSPresto were comparable to those on the FACSCalibur with low absolute (9.5cells/μl) and relative bias (3.2%). Bias in CD4% values was also low (1.06%) with a relative bias of 4.9%. The sensitivity was lower at a CD4 count threshold of ≤350cells/μl compared with ≤500cells/μl (84.9% vs. 92.8%) resulting in a high upward misclassification rate at low CD4 counts. Specificity at thresholds of ≤350cells/μl and ≤500cells/μl were 96.6% and 96.8% respectively. The PIMA had a high absolute (-68.6cells/μl) and relative bias (-10.5%) when compared with the FACSCalibur. At thresholds of ≤350cells/μl and ≤500cells/μl the sensitivity was 100% and 95.5% respectively; specificity was 85.7% and 84.2% respectively. The coefficients of repeatability were 4.13%, 5.29% and 9.8% respectively.

Discussion: The analytic performance of the FACSPresto against the reference standard was very good with better agreement and precision than the PIMA. The FACSPresto had comparable sensitivity at a threshold of 500 cells/μl and better specificity than the PIMA. However the FACSPresto showed reduced sensitivity at low CD4 count thresholds.

Conclusion: The FACSPresto can be reliably used as a POC device for enumerating absolute CD4 count and CD4% values.

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Conflict of interest statement

Competing Interests: BD Biosciences provided regents and test kits and servicing of instruments for the FACSCalibur and FACSPresto. They did not provide an direct grant funding to the project or investigators. They had no role in the design, data analysis or decision to publish. They had no role in reviewing or approving the final manuscript. The authors have no competing interests to declare. There are no employment, consultancy, patents, products in development or marketed products to declare. This did not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Figures

Fig 1
Fig 1. Comparison between FACSPresto and FACSCalibur.
Passing-Bablok regression plot comparison of (a) absolute CD4 count and (c) CD4% values obtained from FACSPresto with the FACSCalibur as reference standard. The solid line represents the regression line and dashed line the 95%CI. Pollock plots indicating %mean bias between (b) absolute CD4 count and (d) CD4% values obtained on FACSPresto compared with those obtained on the FACSCalibur. The solid line represents the mean bias, the dashed line represents mean bias ±1.96SD.
Fig 2
Fig 2. Comparison between PIMA and FACSCalibur and FACSPresto.
(a) Passing-Bablok regression plot comparison of absolute CD4 count between PIMA and FACSCalibur; (b) Pollock plot indicating %mean bias between PIMA and FACSCalibur
See this image and copyright information in PMC

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