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Published on: August 17, 2015
Standardization of C-peptide measurements
Randie R Little1, Curt L Rohlfing, Alethea L Tennill
1Diabetes Diagnostic Laboratory, Department of Pathology & Anatomical Sciences, University of Missouri School of Medicine, Columbia, MO 65212, USA. LittleR@health.missouri.edu
Clinical Chemistry
|April 19, 2008
Summary
Laboratory variations in C-peptide (a marker of insulin secretion) testing can be reduced. Harmonizing results using mass spectrometry calibration improves comparability between different methods and labs for diabetic patients.
Area of Science:
- Clinical Chemistry
- Laboratory Medicine
- Endocrinology
Background:
- C-peptide is a crucial biomarker for assessing insulin secretion in diabetes management.
- Significant variability exists in C-peptide assay performance across different laboratories and methods.
- Standardization is needed to ensure reliable C-peptide measurements for clinical decision-making.
Purpose of the Study:
- To evaluate the imprecision of routine C-peptide assays across multiple laboratories.
- To determine if mass spectrometry-assigned values in serum calibrators can harmonize C-peptide results.
- To improve the comparability of C-peptide measurements for diabetic patients.
Main Methods:
- A multi-laboratory study involving 15 labs and 9 different C-peptide assay methods.
- Analysis of 40 serum samples and matched plasma samples, with some analyzed in duplicate over 4 days.
- Utilized a reference mass spectrometry method for C-peptide quantification and normalization.
Main Results:
- Within- and between-run coefficients of variation (CVs) varied widely (<2% to >18%) across assays.
- Normalization using serum samples significantly enhanced inter-laboratory and inter-method comparability.
- Post-normalization, differences in mean C-peptide responses among laboratories were not statistically significant.
Conclusions:
- Discrepancies in C-peptide results are common across different methods and laboratories, particularly at higher concentrations.
- Imprecision varied significantly, with some methods demonstrating superior consistency.
- Calibrating C-peptide measurements to a reference method, like mass spectrometry, effectively improves laboratory comparability.
