title: An international multicenter performance analysis of cytomegalovirus load tests.
abstract: BACKGROUND
  Quantification of cytomegalovirus (CMV) load is central to the management of CMV infections in immunocompromised patients, but quantitative results currently differ significantly across methods and laboratories.
  
  
  METHODS
  The COBAS AmpliPrep/COBAS TaqMan CMV Test (CAP/CTM CMV test), developed using the first World Health Organization CMV standard in the calibration process, was compared to local assays used by 5 laboratories at transplant centers in the United States and Europe. Blinded plasma panels (n = 90) spiked with 2.18-6.7 log(10) copies/mL and clinical plasma samples from immunocompromised patients (n = 660) were tested.
  
  
  RESULTS
  Observed mean panel member concentrations by site and 95% confidence intervals (CIs) of the data combined across sites were narrower for CAP/CTM CMV test compared with local assays. The 95% CI in log(10) copies/mL of the combined data per panel member for CAP/CTM CMV test vs comparator assays was .17 vs 1.5 at 2.18 log(10) copies/mL; .14 vs .52 at 2.74 log(10) copies/mL; .16 vs .6 at 3.3 log(10) copies/mL; .2 vs 1.11 at 4.3 log(10) copies/mL; .21 vs 1.13 at 4.7 log(10) copies/mL; and .18 vs 1.4 at 6.7 log(10) copies/mL. In clinical specimens, constant and variable quantification differences between the CAP/CTM CMV test and comparator assays were observed.
  
  
  CONCLUSIONS
  High interlaboratory agreement and precision of CAP/CTM CMV test results across 5 different laboratories over 4 orders of magnitude suggest that this assay could be valuable in prospective studies identifying clinical viral load thresholds for CMV treatment.
authors.affiliation: Transplantation and Clinical Virology, Department Biomedicine (Haus Petersplatz), University of Basel, Switzerland. hans.hirsch@unibas.ch
authors.forename: Hans H
authors.initials: HH
authors.lastname: Hirsch
authors.forename: Irmeli
authors.initials: I
authors.lastname: Lautenschlager
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Pinsky
authors.forename: Laura
authors.initials: L
authors.lastname: Cardeñoso
authors.forename: Shagufta
authors.initials: S
authors.lastname: Aslam
authors.forename: Bryan
authors.initials: B
authors.lastname: Cobb
authors.forename: Regis A
authors.initials: RA
authors.lastname: Vilchez
authors.forename: Alexandra
authors.initials: A
authors.lastname: Valsamakis
mesh_terms: D003587:Cytomegalovirus / Q000235:genetics / Q000302:isolation & purification*; D003586:Cytomegalovirus Infections / Q000276:immunology*; D004279:DNA, Viral / Q000032:analysis*; D005060:Europe; D006801:Humans; D016867:Immunocompromised Host / Q000276:immunology; D011237:Predictive Value of Tests; D060888:Real-Time Polymerase Chain Reaction / Q000592:standards*; D012044:Regression Analysis; D015203:Reproducibility of Results; D014481:United States; D019562:Viral Load
chemical_list: D004279:DNA, Viral