Quantification of serum apolipoprotein E and patient phenotyping using isotope dilution liquid chromatography-tandem mass spectrometry / 中华检验医学杂志

ABSTRACT

Objective To establish an isotope dilution liquid chromatography tandem mass spectrometry method (ID-LC-MS) for quantification of serum apolipoprotein E and phenotyping. Methods Method establishment. Samples underwent denaturing, alkylation and trypsin digestion with addition of internal standards as isotope labelling arginine. SB-C18 column was used for the liquid chromatographic separation and mass spectrometry positive ion mode and multiple reaction monitoring were employed for quantification and phenotyping. Precision, accuracy and linearity were investigated for method evaluation. 40 serum samples from Shanghai Dongfang Hospital during Oct. to Dec., 2018 were used for method comparison between ID-LC-MS and immunoassay. Deming regression and Bland-Altman were used for method comparison analysis and SPSS 24 for linearity. Results Target peptides reached their releasing maximum within 4 hours and SE did at 3 hours. 3 phenotyping of ApoE were observed, such as E3/E3, E2/E3 and E3 / E4. The imprecision of IQC was 5.2 ％ . The relative bias for low and high levels of accuracy-based samples was 7.6 ％ and 3.6 ％, respectively. Deming regression showed the intercept with 95 ％ confidence interval (CI) was 6.44-11.44 (P<0.05 and the 95％ confidence interval for the slopewas 0.77-0.89 (P<0.05). The coefficient was r=0.97. The mean difference was - 2.95 mg / L with 95 ％ CI-4.26--1.65 mg/L. The linearity covered from 16.9 to 58.5 mg/L. Conclusion ID-LC-MS can be used to quantify serum apolipoprotein E and simultaneously detect its phenotyping.