title: Evaluation of TruCount absolute-count tubes for determining CD4 and CD8 cell numbers in human immunodeficiency virus-positive adults. Site Investigators and The NIAID DAIDS New Technologies Evaluation Group.
abstract: A single-platform technology that uses an internal bead standard and three-color flow cytometry to determine CD4 and CD8 absolute counts was evaluated for reproducibility and agreement. Values obtained using TruCount absolute-count tubes were compared to those obtained using a two-color predicate methodology. Sixty specimens from human immunodeficiency virus type 1-infected donors were shipped to five laboratories. Each site also analyzed replicates of 14 human immunodeficiency virus type 1-infected local specimens at 6 h and again at 24 h. The interlaboratory variability was significantly less with TruCount (median difference in percent coefficient of variation [%CV] between the two methods was -8% and -3% for CD4 and CD8, respectively) than with the predicate method. Intralaboratory variability was smaller, with a median difference in %CV of -1% for both CD4 and CD8 with 6-h samples and -2% and -3% for CD4 and CD8, respectively, with 24-h samples. Use of TruCount for shipped samples resulted in a median CD4 count change of 7 cells (50th estimated percentile) when all laboratories and CD4 strata were combined. For on-site samples, the median CD4 count change was 10 CD4 cells for 6-h samples and 2 CD4 cells for 24-h samples. Individual site biases occurred in both directions and cancelled each other when the data were combined for all laboratories. Thus, the combined data showed a smaller change in median CD4 count than what may have occurred at an individual site. In summary, the use of TruCount decreased both the inter- and intralaboratory variability in determining absolute CD4 and CD8 counts.
authors.affiliation: Department of Medicine/Infectious Diseases, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA. cschnizl@iupui.edu
authors.forename: C T
authors.initials: CT
authors.lastname: Schnizlein-Bick
authors.forename: J
authors.initials: J
authors.lastname: Spritzler
authors.forename: C L
authors.initials: CL
authors.lastname: Wilkening
authors.forename: J K
authors.initials: JK
authors.lastname: Nicholson
authors.forename: M R
authors.initials: MR
authors.lastname: O'Gorman
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000175:diagnosis* / Q000276:immunology*; D000328:Adult; D016516:CD4-CD8 Ratio / Q000379:methods*; D005434:Flow Cytometry / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D015497:HIV-1; D006405:Hematology / Q000379:methods / Q000592:standards; D006801:Humans; D007755:Laboratories, Hospital / Q000592:standards; D015203:Reproducibility of Results; D013048:Specimen Handling