title: Conversion, correction, and International Scale standardization: results From a Multicenter External Quality Assessment Study for BCR-ABL1 testing.
abstract: BACKGROUND
  Monitoring BCR-ABL1 expression levels relative to clinically validated response criteria on the International Scale (IS) is vital in the optimal management of patients with chronic myeloid leukemia, yet significant variability remains across laboratories worldwide.
  
  
  OBJECTIVE
  To assess method performance, interlaboratory precision, and different IS standardization modalities in representative laboratories performing routine BCR-ABL1 testing.
  
  
  METHODS
  Fifteen blinded test specimens with 5-level nominal BCR-ABL1 to ABL1 IS percentage ratios ranging from 5% to 0.0005% and 4-level secondary IS reference panels, the ARQ IS Calibrator Panels, were tested by relative quantitative polymerase chain reaction in 15 laboratories in 5 countries. Both raw and IS percentage ratios calculated by using local conversion factors (CFs) or analytic correction parameters (CPs) were collected and analyzed.
  
  
  RESULTS
  A total of 670 valid positive results were generated. BCR-ABL1 detection was associated with variable ABL1 quality metric passing rates (P < .001) and reached at least 0.01% in 13 laboratories. Intralaboratory precision was within 2.5-fold for all sample levels combined with a relative mean difference greater than 5-fold across laboratories. International Scale accuracy was increased by using both the CF and CP standardization methods. Classification agreement for major molecular response status was 90% after CF conversion and 93% after CP correction, with precision improved by 3-fold for the CP method.
  
  
  CONCLUSIONS
  Despite preanalytic and analytic differences between laboratories, conversion and correction are effective IS standardization methods. Validated secondary reference materials can facilitate global diffusion of the IS without the need to perform sample exchange and improve the accuracy and precision of BCR-ABL1 quantitative measurements, including at low levels of residual disease.
authors: From West Midlands Regional Genetics Laboratory, Birmingham Women's NHS Foundation Trust, and School of Cancer Sciences, University of Birmingham, Birmingham, United Kingdom (Mr Griffiths); the European Molecular Genetics Quality Network, Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester, United Kingdom (Dr Patton); Oncology Unit, Ospedale di Prato, Prato, Italy (Dr Grossi); United Kingdom National External Quality Assessment Schemes, Sheffield, United Kingdom (Mr Clark); Labceutics, Belfast, United Kingdom (Dr Fe Paz); and Asuragen, Austin, Texas (Dr Labourier). Mr Clark is now with Labceutics, Belfast, United Kingdom.
authors: Michael
authors: M
authors: Griffiths
authors: Simon J
authors: SJ
authors: Patton
authors: Alberto
authors: A
authors: Grossi
authors: Jordan
authors: J
authors: Clark
authors: Maria Fe
authors: MF
authors: Paz
authors: Emmanuel
authors: E
authors: Labourier
mesh_terms: D002984:Clinical Laboratory Information Systems; D019411:Clinical Laboratory Techniques / Q000379:methods / Q000592:standards; D016044:Fusion Proteins, bcr-abl / Q000235:genetics*; D015973:Gene Expression Regulation, Leukemic; D005820:Genetic Testing / Q000379:methods* / Q000592:standards*; D018922:HL-60 Cells; D006801:Humans; D007391:International Cooperation; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000175:diagnosis / Q000235:genetics*; D011786:Quality Control; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D016044:Fusion Proteins, bcr-abl