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Published on: July 1, 2014
An Accurate Isotope Dilution Liquid Chromatography-Tandem Mass Spectrometry Method for Serum C-Peptide and Its Use in
Yuhang Deng1, Chao Zhang2, Jing Wang2
1National Center for Clinical Laboratories, Beijing Engineering Research Center of Laboratory Medicine, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, China.
Background:
Serum C-peptide results from various routine methods used in China are highly variable, warranting well-performing methods to serve as an accuracy base to improve the harmonization of C-peptide measurements in China. We developed an accurate isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) method for serum C-peptide measurement and explored its use in harmonization.
Methods:
After protein precipitation with ZnSO4 solution, C-peptide was extracted from serum samples by anion-exchange solid-phase extraction and quantified by ID-LC-MS/MS in positive ion mode. The precision and analytical recovery of the ID-LC-MS/MS method were assessed. Seventy-six serum samples were analyzed using the ID-LC-MS/MS method and six routine immunoassays. Ordinary linear regression (OLR) and Bland-Altman (BA) analyses were conducted to evaluate the relationship between the ID-LC-MS/MS method and routine immunoassays. Five serum pool samples assigned using the ID-LC-MS/MS method were used to recalibrate the routine assays. OLR and BA analyses were re-conducted after recalibration.
Results:
The within-run, between-run, and total precision for the ID-LC-MS/MS method at four concentrations were 1.0%-2.1%, 0.6%-1.2%, and 1.3%-2.2%, respectively. The analytical recoveries for the ID-LC-MS/MS method at three concentrations were 100.3%-100.7%, 100.4%-101.0%, and 99.6%-100.7%. The developed method and the immunoassays were strongly correlated, with all R2 >0.98. The comparability among the immunoassays was substantially improved after recalibration.
Conclusions:
The performance of the ID-LC-MS/MS method was carefully validated, and this method can be used to improve the harmonization of serum C-peptide measurements in China.
