title: Flow rate calibration II: a clinical evaluation study using PanLeucoGating as a single-platform protocol.
abstract: BACKGROUND
  CD4(+) T-lymphocyte enumeration is vital for monitoring disease progression in individuals positive for the human immunodeficiency virus (HIV), and as a result, there is a need to develop cost-effective protocols that provide accuracy, precision, and affordability. Recently, PanLeucoGating has been shown to fulfill these requirements; however, although comparable to state-of-the-art single-platform protocols (SP), there is still a requirement for an accurate total white cell count. To overcome this limitation, we recently developed a flow-rate based calibration method that enables the PanLeucoGating protocol to be used as a SP approach, and in this study show that this approach can be used for CD4(+) T-lymphocyte enumeration.
  
  
  METHODS
  A total of 113 HIV samples were analyzed using three protocols: (a) state-of-the art SP bead-based method (MultiSet; predicate protocol), (b) PanLeucoGating protocol used as a dual-platform (DP) approach, and (c) the newly developed flow rate-based SP approach. We demonstrate that flow rate calibration can be achieved easily and that the method is highly comparable to the state-of-the-art SP method.
  
  
  RESULTS
  A high correlation was observed between the predicate protocol and the SP PanLeucoGating approach over the whole range of CD4 counts tested (r(2) = 0.9928; bias 8 cells/microl), including the clinically relevant range (e.g., 0-200 CD4 cells/microl; bias 0 cells/microl). For batched samples, the cost of providing a CD4(+) T-lymphocyte count was reduced to approximately US $1.
  
  
  CONCLUSIONS
  The SP PanLeucoGating is a cost-effective approach to CD4(+) T-lymphocyte enumeration that maintains accuracy and precision.
authors.affiliation: UK NEQAS for Leucocyte Immunophenotyping, Royal Hallamshire Hospital, Sheffield, United Kingdom.
authors.forename: Ian
authors.initials: I
authors.lastname: Storie
authors.forename: Alex
authors.initials: A
authors.lastname: Sawle
authors.forename: Liam
authors.initials: L
authors.lastname: Whitby
authors.forename: Karen
authors.initials: K
authors.lastname: Goodfellow
authors.forename: Vivian
authors.initials: V
authors.lastname: Granger
authors.forename: John T
authors.initials: JT
authors.lastname: Reilly
authors.forename: David
authors.initials: D
authors.lastname: Barnett
mesh_terms: D000818:Animals; D018791:CD4 Lymphocyte Count / Q000191:economics / Q000379:methods*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000821:virology; D002138:Calibration; D005069:Evaluation Studies as Topic; D005434:Flow Cytometry / Q000191:economics / Q000379:methods*; D015658:HIV Infections / Q000503:physiopathology; D006801:Humans; D011786:Quality Control; D012680:Sensitivity and Specificity