title: Clinical Evaluation of the BD FACSPresto™ Near-Patient CD4 Counter in Kenya.
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.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT02396355.
authors.affiliation: Kenya Medical Research Institute/US CDC Research and Public Health Collaboration, Kisumu, Kenya.
authors.forename: Francis
authors.initials: F
authors.lastname: Angira
authors.affiliation: Kenya Medical Research Institute/US CDC Research and Public Health Collaboration, Kisumu, Kenya.
authors.forename: Benta
authors.initials: B
authors.lastname: Akoth
authors.affiliation: Kenya Medical Research Institute/US CDC Research and Public Health Collaboration, Kisumu, Kenya.
authors.forename: Paul
authors.initials: P
authors.lastname: Omolo
authors.affiliation: Kenya Medical Research Institute/US CDC Research and Public Health Collaboration, Kisumu, Kenya.
authors.forename: Valarie
authors.initials: V
authors.lastname: Opollo
authors.affiliation: BD Biosciences, 2350 Qume Drive, San Jose, California, United States of America.
authors.forename: Scott
authors.initials: S
authors.lastname: Bornheimer
authors.affiliation: BD Biosciences, 2350 Qume Drive, San Jose, California, United States of America.
authors.forename: Kevin
authors.initials: K
authors.lastname: Judge
authors.affiliation: BD Biosciences, 2350 Qume Drive, San Jose, California, United States of America.
authors.forename: Henok
authors.initials: H
authors.lastname: Tilahun
authors.affiliation: BD Biosciences, 2350 Qume Drive, San Jose, California, United States of America.
authors.forename: Beverly
authors.initials: B
authors.lastname: Lu
authors.affiliation: BD Biosciences, 2350 Qume Drive, San Jose, California, United States of America.
authors.forename: Imelda
authors.initials: I
authors.lastname: Omana-Zapata
authors.affiliation: US Centers for Disease Control and Prevention (CDC-Kenya), Kisumu, Kenya.
authors.forename: Clement
authors.initials: C
authors.lastname: Zeh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D018791:CD4 Lymphocyte Count / Q000379:methods*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D015658:HIV Infections / Q000097:blood* / Q000276:immunology; D006801:Humans; D007630:Kenya / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D055815:Young Adult