The reference method was established and validated according to the Joint Committee for Traceability in Laboratory Medicine (JCTLM). Accuracy and precision of the reference method were assessed by SRM 909c and RELA samples. It was then used to assign values of creatinine to fresh frozen serum samples from small molecule accuracy investigation schemes gathering with Shanghai clinical laboratories.

The relative bias of the reference method was 0.69%, and imprecision was < 2%. For the sample 201411, 201412, 201421 and 201422, the relative biases from reference method were 14.97%, -2.77%, -1.37% and -1.92% for enzymatic test results, respectively, and were 21.39%, 2.10%, 6.22% and 2.38% for the Jaffe test results, respectively. The relative bias of all the samples with different systems from reference method was less than 8% except for the sample 201411 with low concentration.

The ID-LC/MS/MS method established for serum creatinine has good precision and accuracy, and the determination of the target value is of great importance on the result analysis of laboratories. It is expected to play a role in the trueness verification of clinical laboratories in Shanghai area. Therefore, this study highlights that the clinical laboratories should attach great importance to measurement accuracy and consistency with low concentration of creatinine.