The transferability of a candidate reference method for determination of creatinine in serum

We developed a candidate reference method for the determination of creatinine in serum. For the acceptance of a reference method it is important that it be rigorously validated against a definitive method and that the method can be transferred from one laboratory to another. This study focussed on the transferability and consisted of two parts: introduction and familiarization with the method in four clinical chemistry laboratories in the Netherlands, followed by independent measurements of Standard Reference Material 909a2 and several commercial quality control materials provided with reference method values according to the protocol of the German Quality Assessment Organisation. The criterion for judging transferability was the mean total error (%) of the five sera used in the accuracy experiment. For creatinine we used a total error of < 2.2%. For Standard Reference Material 909a2 all four laboratories were able to comply with this demand, while only two laboratories met this requirement for the other four sera. The results for the Standard Reference Material 909a2 from the collaborating laboratories demonstrate that this candidate reference method can be successfully transferred without loss of precision and accuracy.