title: Assessing immunophenotyping performance: proficiency-validation for adopting improved flow cytometry methods.
abstract: BACKGROUND
  The continuous improvement and evolution of immune cell phenotyping requires periodic upgrading of laboratory methods and technology. Flow cytometry laboratories that are participating in research protocols sponsored by the NIAID are required to perform "switch" studies to validate performance before methods for T-cell subset analysis can be changed.
  
  
  METHODS
  Switch studies were conducted among the four flow cytometry laboratories of the Multicenter AIDS Cohort Study (MACS), comparing a 2-color, lyse-wash method and a newer, 3-color, lyse no-wash method. Two of the laboratories twice failed to satisfy the criteria for acceptable differences from the previous method. Rather than repeating more switch studies, these laboratories were allowed to adopt the 3-color, lyse no-wash method. To evaluate the impact of the switch to the new method at these two sites, their results with the new method were evaluated within the context of all laboratories participating in the NIH-NIAID-Division of AIDS Immunology Quality Assurance (IQA) proficiency-testing program.
  
  
  RESULTS
  Laboratory performance at these two sites substantially improved relative to the IQA standard test results. Variation across the four MACS sites and across replicate samples was also reduced.
  
  
  CONCLUSIONS
  Although switch studies are the conventional method for assessing comparability of laboratory methods, two alternatives to the requirement of repeating failed switch studies should be considered: (1) test the new method and assess performance on the proficiency testing reference panel, and (2) prior to adoption of the new methods, use both the old and the new method on the reference panel samples and demonstrate that performance with the new method is better according to standard statistical procedures. These alternatives may help some laboratories' transition to a new and superior methodology more quickly than if they are required to attempt multiple, serial switch studies.
authors.affiliation: Department of Medicine, Cellular Immunology and Cytometry, University of California, Los Angeles, California, USA.
authors.forename: Lance E
authors.initials: LE
authors.lastname: Hultin
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Menendez
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Hultin
authors.forename: Beth D
authors.initials: BD
authors.lastname: Jamieson
authors.forename: Maurice R G
authors.initials: MR
authors.lastname: O'Gorman
authors.forename: Luann
authors.initials: L
authors.lastname: Borowski
authors.forename: Jose L
authors.initials: JL
authors.lastname: Matud
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Denny
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Margolick
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000175:diagnosis / Q000276:immunology; D000954:Antigens, Surface / Q000276:immunology; D015331:Cohort Studies; D005434:Flow Cytometry / Q000379:methods* / Q000639:trends; D006801:Humans; D016130:Immunophenotyping / Q000379:methods* / Q000592:standards / Q000639:trends; D015588:Observer Variation; D011237:Predictive Value of Tests; D011786:Quality Control; D015203:Reproducibility of Results; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000954:Antigens, Surface