1. ¹III. Medizinische Universitätsklinik, Medizinische Fakultät Mannheim der Universität Heidelberg, Mannheim, Germany
2. ²Division of Hematology and Internal Medicine, Department of Clinical and Biological Sciences, University of Turin, Turin, Italy
3. ³Department of Hematology, Aarhus University Hospital, Aarhus, Denmark

Correspondence: Dr MC Müller, III. Medizinische Universitätsklinik, Medizinische Fakultät Mannheim der Universität Heidelberg, Wiesbadener Strasse 7-11, Mannheim 68305, Germany. E-mail: martin.mueller@med3.ma.uni-heidelberg.de

⁴These authors contributed equally to this work.

Received 20 May 2007; Revised 7 August 2007; Accepted 12 September 2007; Published online 18 October 2007.

Abstract

Individualized PCR strategies hamper comparability of molecular results between different laboratories in several fields of medicine. To harmonize BCR-ABL mRNA quantification an international multicenter trial involving 37 laboratories in 14 countries was initiated using 10 samples, each containing various dilutions (10, 2, 1 and 0.1%) of b3a2 or b2a2 BCR-ABL positive in normal leukocytes and negative controls. A novel control plasmid (pME-2) was designed for external calibration containing BCR-ABL and glucuronidase- (GUS) sequences. Median BCR-ABL/ABL ratios were 9.1, 1.8, 0.85 and 0.11% in b3a2 samples and 9.5, 1.6, 0.84 and 0.11% in b2a2 samples. Median BCR-ABL/GUS ratios were 3.4, 0.77, 0.37 and 0.042% in b3a2 samples and 2.8, 0.48, 0.29 and 0.031% in b2a2 samples. The coefficients of variation were 0.62 for ratios BCR-ABL/ABL and 1.03 for ratios BCR-ABL/GUS. Five of 37 evaluable participating laboratories (13%) detected low BCR-ABL copy numbers in negative control samples; one laboratory failed to detect BCR-ABL in a low-level sample. We conclude that the use of a common control plasmid does indeed improve comparability of BCR-ABL mRNA quantification results. However, further standardizing efforts like introducing a calibrator and regular control rounds are needed.