title: Performance of FACSPresto Point-of-Care Instrument for CD4-T Cell Enumeration in Human Immunodeficiency Virus (HIV)-Infected Patients Attending Care and Treatment Clinics in Belgium and Tanzania.
abstract: BACKGROUND
  CD4 T-cell counts are widely used to assess treatment eligibility and to follow-up HIV-infected patients. The World Health Organization prequalification of in vitro diagnostics program conducted a performance evaluation of the FACSPresto (BD Biosciences), a new point-of-care instrument to measure absolute CD4-T cell (CD4) counts and percentages in venous and capillary blood samples from HIV-infected patients.
  
  
  METHODS
  Patients were recruited in Belgium (200 patients) and in Tanzania (247 patients). Venous blood samples were analyzed in two nearby reference laboratories. In addition, nurses/technicians collected a capillary blood sample by finger prick directly into a FACSPresto CD4 cartridge. Assay precision was assessed on fresh blood and on external quality control samples. Trueness (bias) was assessed by comparing results from FACSPresto with the reference (single-platform FACSCalibur). Clinical misclassification was measured at 200, 350 and 500 cells/μL thresholds.
  
  
  RESULTS
  Intra-assay precision was < 6%, and inter-assay < 8%. CD4 results from FACSPresto and reference method resulted in regression slopes of 0.99-1.11 using either venous or capillary blood. Correlation was better for venous than for capillary blood (minimum 0.97 vs 0.93 respectively). Capillary blood resulted in a larger bias than venous blood, with 24 and 83 cells/μL for absolute CD4 counts on capillary blood in Antwerp and Dar es Salaam respectively, vs 12 and 41 cells/μL on venous blood. Bias on CD4% was < 1% on both venous and capillary blood, and was proportionally better than for absolute CD4 counts. Clinical misclassification was in line with the average overestimation, showing a very good specificity, but sensitivity around 70-90%. The rejection rate was 11% on first reading, leading to 6% of all samples without final result after a second reading.
  
  
  CONCLUSIONS
  The FACSPresto performed very well on venous blood samples, and well on capillary blood samples.
authors.affiliation: Laboratory of Immunology, Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.
authors.forename: Géraldine
authors.initials: G
authors.lastname: Daneau
authors.affiliation: Department of Microbiology and Immunology, Muhimbili University of Health and Allied Sciences (MUHAS) Dar es Salaam, Tanzania.
authors.forename: Said
authors.initials: S
authors.lastname: Aboud
authors.affiliation: World Health Organisation (WHO), Geneva, Switzerland.
authors.forename: Irena
authors.initials: I
authors.lastname: Prat
authors.affiliation: World Health Organisation (WHO), Geneva, Switzerland.
authors.forename: Willy
authors.initials: W
authors.lastname: Urassa
authors.affiliation: Laboratory of Immunology, Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.|Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium.
authors.forename: Luc
authors.initials: L
authors.lastname: Kestens
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D023241:Antiretroviral Therapy, Highly Active; D001530:Belgium / Q000453:epidemiology; D001800:Blood Specimen Collection; D018791:CD4 Lymphocyte Count; D015496:CD4-Positive T-Lymphocytes / Q000473:pathology* / Q000821:virology; D005260:Female; D005434:Flow Cytometry; D006678:HIV / Q000302:isolation & purification / Q000472:pathogenicity*; D015658:HIV Infections / Q000097:blood* / Q000188:drug therapy / Q000453:epidemiology* / Q000821:virology; D006801:Humans; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems; D013636:Tanzania / Q000453:epidemiology; D014944:World Health Organization