Applicability of common reference intervals for serum creatinine concentrations to the Croatian population

Background: In accordance with an ongoing activity for worldwide harmonization based on traceability in laboratory methods, the goal of this study was to validate the applicability of recommended "common" reference intervals for serum creatinine concentrations using a specific enzymatic method to the Croatian population. Methods: The reference group consisted of 240 healthy subjects (120 males and 120 females), between 18 and 74 years of age (median 57 years), who were selected in accordance with the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) recommendations. Creatinine in serum was measured using the creatinine enzymatic assay (Olympus OSR61204) that was standardized to the isotopic dilution mass spectrometry (IDMS) method and National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 967. In addition, creatinine was measured using a kinetic Jaffe method (Olympus OSR6178) standardized to NIST SRM 909b level 2 standard. Results: Method comparison between enzymatic creatinine (x) and the Jaffe kinetic method (y) gave the following P/B equation for the entire group (n = 240): y = 1.00x + 17.00; r = 0.968. Reference intervals for serum creatinine (central 95th percentiles) obtained using the enzymatic creatinine method ranged from 54 to 107 mu mol/L for males and from 50 to 93 mu mol/L for females. The IFCC recommended common reference intervals for global applications are 64-104 mmol/L and 49-90 mu mol/L for males and females, respectively. Conclusions: Comparability of obtained results confirmed the applicability of recently recommended "common" reference intervals to the Croatian population for all laboratories measuring serum creatinine concentrations using enzymatic methods traceable to the IDMS method and NIST SRM 967. Clin Chem Lab Med 2010;48: 231-5.