An LC–MS/MS method for serum cystatin C quantification and its comparison with two commercial immunoassays
Author:
Zhang Li12, Nizhamuding Xiaerbanu12, Zheng Hao13, Zeng Jie13, Yuan Xinyi12, Ma Zijia12, Zhou Weiyan13ORCID, Zhang Chao13, Zhang Tianjiao13, Zhang Chuanbao13ORCID
Affiliation:
1. National Center for Clinical Laboratories, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences , Beijing Hospital , Beijing , P.R. China 2. National Center of Gerontology, Beijing Engineering Research Center of Laboratory Medicine , Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing , P.R. China 3. National Center of Gerontology , Beijing Engineering Research Center of Laboratory Medicine , Beijing , P.R. China
Abstract
Abstract
Objectives
The standardization of cystatin C (CysC) measurement has received increasing attention in recent years due to its importance in estimating glomerular filtration rate (GFR). Mass spectrometry-based assays have the potential to provide an accuracy base for CysC measurement. However, a precise, accurate and sustainable LC–MS/MS method for CysC is still lacking.
Methods
The developed LC–MS/MS method quantified CysC by detecting signature peptide (T3) obtained from tryptic digestion. Stable isotope labeled T3 peptide (SIL-T3) was spiked to control matrix effects and errors caused by liquid handling. The protein denaturation, reduction and alkylation procedures were combined into a single step with incubation time of 1 h, and the digestion lasted for 3.5 h. In the method validation, digestion time-course, imprecision, accuracy, matrix effect, interference, limit of quantification (LOQ), carryover, linearity, and the comparability to two routine immunoassays were evaluated.
Results
No significant matrix effect or interference was observed with the CysC measurement. The LOQ was 0.21 mg/L; the within-run and total imprecision were 1.33–2.05 % and 2.18–3.90 % for three serum pools (1.18–5.34 mg/L). The LC–MS/MS method was calibrated by ERM-DA471/IFCC and showed good correlation with two immunoassays traceable to ERM-DA471/IFCC. However, significant bias was observed for immunoassays against the LC–MS/MS method.
Conclusions
The developed LC–MS/MS method is robust and simpler and holds the promise to provide an accuracy base for routine immunoassays, which will promote the standardization of CysC measurement.
Funder
National Key Research and Development Program of China Beijing Natural Science Foundation
Publisher
Walter de Gruyter GmbH
Subject
Biochemistry (medical),Clinical Biochemistry,General Medicine
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