Introduction: To perform comparability of instruments, the laboratory can select patient samples spanning the reportable range or can use plasma sets from commercial suppliers. We evaluated ExpertCor Routine (ECR) plasma set (Stago), a set of frozen plasmas enabling to verify the agreement between different coagulation analysers. Additionally, we evaluated whether the concept of transference of the reference range is acceptable between instruments, once comparability between the instruments is approved.
Methods: Patient samples and the ECR plasma set were evaluated for method comparison for prothrombin time, activated partial thromboplastin time and fibrinogen on five instruments. Results of one instrument were compared to the mean of all analysers by Passing-Bablok regression and Bland-Altman analysis. Reference ranges were checked on all instruments.
Results: The %mean difference was ≤5% and ≤3.7% for all analyser/parameter combinations, for ECR and patient sample data sets, respectively. All predefined criteria to fulfil good comparability between instruments were met. The between-instrument comparison with the ECR plasma set and the patient samples was equal for PT, INR and fibrinogen. After demonstrating comparability between instruments by either of the two plasma sample sets, reference ranges can be used interchangeably between identical instruments.
Conclusion: Instrument-to-instrument reproducibility showed comparable results using a data set obtained with patient samples or a commercial plasma set. Once comparability between instruments is confirmed, defined reference ranges can be transferred from one instrument to the other instrument without additional testing. The ECR plasma set is a good alternative to the use of local patient samples to evaluate instrument comparability.
Keywords: analytical performance; coagulation; comparability; method validation; reference interval; transference.
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