Jaffe's kinetic method comparison between isotope dilution mass spectrometry standardized versus nonstandardized method

Abstract

INTRODUCTION: Serum creatinine is estimated by several methods in different laboratories, having varying degrees of bias and imprecision, leading to different values across the laboratories with the same sample. To reduce the interlaboratory variations in creatinine assay, creatinine standardization program was established by the National Kidney Disease Education Program Laboratory Working Group and recommended that creatinine calibration should be done with material traceable to an Isotope dilution mass spectrometry (IDMS) reference measurement procedure. AIMS AND OBJECTIVE: To compare the serum creatinine estimated by CRE (calibration nonstandardized IDMS with correction factor) and CRE2 (standardized to IDMS) method. MATERIALS AND METHODS: The study was conducted in a tertiary care hospital as a part of validation of CRE2 method. Two hundred samples were selected from individuals aged between 18 and 60 years with normal serum urea, creatinine, and electrolytes based on the CRE2 method. Further, the sample is estimated for serum creatinine by CRE method on the same instrument with a correction factor (Siemens Dimension RXL with LM). Descriptive statistics and Bland–Altman analysis were used to describe the population and check for agreement between the methods. RESULTS AND CONCLUSION: The average serum creatinine by CRE and CRE2 method was 0.803 mg/dl and 0.809 mg/dl, respectively. Bland–Altman plot shows a good agreement between the methods for serum creatinine with a mean bias of − 0.01 mg/dL for serum creatinine values ranging from 0.4 to 1.4 mg/dL.