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Clinical Trial
. 2016 Aug 2;11(8):e0157939.
doi: 10.1371/journal.pone.0157939. eCollection 2016.

Clinical Evaluation of the BD FACSPresto™ Near-Patient CD4 Counter in Kenya

Francis Angira  1 , Benta Akoth  1 , Paul Omolo  1 , Valarie Opollo  1 , Scott Bornheimer  2 , Kevin Judge  2 , Henok Tilahun  2 , Beverly Lu  2 , Imelda Omana-Zapata  2 , Clement Zeh  3
Affiliations
Clinical Trial

Clinical Evaluation of the BD FACSPresto™ Near-Patient CD4 Counter in Kenya

Francis Angira et al. PLoS One. .

Abstract

Background: The BD FACSPresto™ Near-Patient CD4 Counter was developed to expand HIV/AIDS management in resource-limited settings. It measures absolute CD4 counts (AbsCD4), percent CD4 (%CD4), and hemoglobin (Hb) from a single drop of capillary or venous blood in approximately 23 minutes, with throughput of 10 samples per hour. We assessed the performance of the BD FACSPresto system, evaluating accuracy, stability, linearity, precision, and reference intervals using capillary and venous blood at KEMRI/CDC HIV-research laboratory, Kisumu, Kenya, and precision and linearity at BD Biosciences, California, USA.

Methods: For accuracy, venous samples were tested using the BD FACSCalibur™ instrument with BD Tritest™ CD3/CD4/CD45 reagent, BD Trucount™ tubes, and BD Multiset™ software for AbsCD4 and %CD4, and the Sysmex™ KX-21N for Hb. Stability studies evaluated duration of staining (18-120-minute incubation), and effects of venous blood storage <6-24 hours post-draw. A normal cohort was tested for reference intervals. Precision covered multiple days, operators, and instruments. Linearity required mixing two pools of samples, to obtain evenly spaced concentrations for AbsCD4, total lymphocytes, and Hb.

Results: AbsCD4 and %CD4 venous/capillary (N = 189/ N = 162) accuracy results gave Deming regression slopes within 0.97-1.03 and R2 ≥0.96. For Hb, Deming regression results were R2 ≥0.94 and slope ≥0.94 for both venous and capillary samples. Stability varied within 10% 2 hours after staining and for venous blood stored less than 24 hours. Reference intervals results showed that gender-but not age-differences were statistically significant (p<0.05). Precision results had <3.5% coefficient of variation for AbsCD4, %CD4, and Hb, except for low AbsCD4 samples (<6.8%). Linearity was 42-4,897 cells/μL for AbsCD4, 182-11,704 cells/μL for total lymphocytes, and 2-24 g/dL for Hb.

Conclusions: The BD FACSPresto system provides accurate, precise clinical results for capillary or venous blood samples and is suitable for near-patient CD4 testing.

Trial registration: ClinicalTrials.gov NCT02396355.

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Conflict of interest statement

Competing Interests: S. Bornheimer, B. Lu, H. Tilahun, K. Judge and I. Omana-Zapata are employees of BD Biosciences. This does not alter the authors' adherence to PLOS ONE policies on sharing data and materials. The BD FACSPresto system is available as CE-IVD and FDA IVD marked product. The findings and conclusions in this article are those of the authors, and do not necessary represent the view of the US Centers for Disease Control and Prevention. Use of trade names is for identification purposes only and does not constitute endorsement by the US Centers for Disease Controls and Prevention or the Department of Health and Human Services.

Figures

Fig 1
Fig 1. Clinical Evaluation of the BD FACSPresto™ Near Patient CD4 Counter Flowchart.
The clinical evaluation of the BD FACSPresto was carried out at KEMRI/CDC and BD Biosciences comprised of the five sub-studies depicted in the flowchart. KEMRI/CDC evaluated the FACSPresto system using venous and capillary blood specimens from subjects attending to the clinic for routine visit. Two analytical sub- studies using normal blood and process control materials were completed at BD Biosciences.
Fig 2
Fig 2. Bland-Altman Plots for AbsCD4, %CD4 and Hb in Venous and Capillary Blood.
Bias results are illustrated in the Bland-Altman plots with limits of agreement for venous blood (2A, 2C and 2E) on the left side and for capillary blood (2B, 2D and 2F) on the right side. Biases for AbsCD4 are show in 2A and 2B; for %CD4 in 2C and 2D and hemoglobin in 2E and 2F. The x-axis displays the average (AbsCD4, %CD4 or Hb) and the y-axis is the difference (AbsCD4, %CD4 or Hb).
Fig 3
Fig 3. Comparison of Venous and Capillary Blood on the BD FACSPresto.
Comparison of venous and capillary Deming regression results are shown for AbsCD4 (A), %CD4 (B), and Hb (C) with R2 (%), intercept, and slope.
See this image and copyright information in PMC

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