title: A North American multilaboratory study of CD4 counts using flow cytometric panLeukogating (PLG): a NIAID-DAIDS Immunology Quality Assessment Program Study.
abstract: BACKGROUND
  The global HIV/AIDS pandemic and guidelines for initiating anti-retroviral therapy (ART) and opportunistic infection prophylaxis demand affordable, reliable, and accurate CD4 testing. A simple innovative approach applicable to existing technology that has been successfully applied in resource-challenged settings, PanLeukogated CD4 (PLG), could offer solutions for cost saving and improved precision.
  
  
  METHODS
  Day-old whole blood from 99 HIV+ donors was simultaneously studied in five North-American laboratories to compare the performance of their predicate methods with the dual-platform PLG method. The predicate technology included varying 4-color CD45/CD3/CD4/CD8 protocols on different flow cytometers. Each laboratory also assayed eight replicate specimens of day-old blood from 10 to 14 local donors. Bias and precision of predicate and PLG methods was studied between- and within-participating laboratories.
  
  
  RESULTS
  Significantly (P < 0.0001) improved between-laboratory precision/coefficient of variation (CV%) was noted using the PLG method (overall median 9.3% vs. predicate median CV 13.1%). Within-laboratory precision was also significantly (P < 0.0001) better overall using PLG (median 4.6% vs. predicate median CV 6.2%) and in 3 of the 5 laboratories. PLG counts tended to be 11% smaller than predicate methods (P < 0.0001) for shipped (median of predicate-PLG = 31) and local specimens (median of predicate-PLG = 23), both overall and in 4 of 5 laboratories (median decreases of 4, 16, 20, and 21% in shipped specimens); the other laboratory had a median increase of 5%.
  
  
  CONCLUSIONS
  Laboratories using predicate CD4 methods similar to those in this study could improve their between-laboratory and their within-laboratory precision, and reduce costs, by switching to the PLG method after adequate training, if a change (usually, a decrease) in CD4 counts is acceptable to their health systems.
authors: Human Vaccine Institute, Duke University Medical Center, Durham, USA. thomas.denny@duke.edu
authors: Thomas N
authors: TN
authors: Denny
authors: Rebecca
authors: R
authors: Gelman
authors: Michele
authors: M
authors: Bergeron
authors: Alan
authors: A
authors: Landay
authors: Lee
authors: L
authors: Lam
authors: Raul
authors: R
authors: Louzao
authors: Frank F
authors: FF
authors: Mandy
authors: John
authors: J
authors: Schmitz
authors: Thomas
authors: T
authors: Spira
authors: Cindy
authors: C
authors: Wilkening
authors: Deborah K
authors: DK
authors: Glencross
mesh_terms: D015982:Bias; D001772:Blood Cell Count; D018791:CD4 Lymphocyte Count / Q000379:methods* / Q000592:standards*; D005434:Flow Cytometry / Q000379:methods*; D006801:Humans; D007753:Laboratories; D007962:Leukocytes / Q000166:cytology; D009656:North America; D011785:Quality Assurance, Health Care; D013048:Specimen Handling