Verification of a previously obtained EQA based MUC1/CA15-3 harmonisation procedure

ObjectivesMUC1/CA 15-3 is the most widely used circulating marker for monitoring treatment in patients with advanced breast cancer. Previous studies demonstrated that MUC1/CA 15-3 tests are insufficiently harmonised and an EQA-based harmonisation procedure has been developed. This study aims to validate the obtained MUC1/CA 15-3 harmonisation procedure and to explore the suitability of MUC1/CA 15-3 materials as a base for developing future MUC1/CA 15-3 reference materials.MethodsSera from 45 patients were obtained and five additional samples were prepared from commercial MUC1/CA 15-3 materials. All samples were analyzed by measurement procedures of Abbott Alinity, Beckman DxI, Roche Cobas and Siemens Atellica. Data analysis included application of the previously obtained MUC1/CA 15-3 harmonisation procedure that required recalibration of Beckman DxI only, pre-and post-harmonisation Passing-Bablok regression, Spearman correlation coefficient and Bland-Altman difference analyses. Suitability of the MUC1/CA 15-3 materials as basis of future standards was also investigated.ResultsThe slopes obtained from the regression analysis of individual MUC1/CA15-3 assays ranged from 0.598 to 1.96 pre-harmonisation and 0.8448 to 1.150 post-harmonisation. The mean difference of individual measurement procedures with the consensus mean improved from -26.65% to 22.83% before harmonisation to -12.78% to 10.95% after harmonisation. The difference between the MUC1/CA 15-3 spiked materials and the patient sample mean differences were ≤10,1% and fell within the 95% limits of agreement.ConclusionsThe EQA-based mathematical harmonisation procedure for MUC1/CA 15-3 resulted in improved MUC1/CA 15-3 harmonisation with real-world clinical samples. The MUC1/CA 15-3 materials provided a suitable base for further exploration as reference materials.