title: Validation and comparison of a rapid liquid chromatography tandem mass spectrometry method for serum 25OHD with the efficiency of separating 3-epi 25OHD3.
abstract: OBJECTIVE
  To develop a rapid liquid chromatography tandem mass spectrometry (LC-MS/MS) method with ability to separate 3-epi 25OHD3 (EPI-LC-MS/MS) from 25OHD3, and evaluate the effects of 3-epi 25OHD3 on routine LC-MS/MS that cannot separate 3-epi 25OHD3 (NEPI-LC-MS/MS).
  
  
  METHODS
  Performance of the newly built EPI-LC-MS/MS was validated, and 982 samples were analyzed and compared by the two methods.
  
  
  RESULTS
  Both methods showed a linearity coefficient correlation exceeding 0.999 in the 6.25-500nmol/L range for 25OHD2 and 25OHD3. Moreover, they showed a between run coefficient variation (CV) and total CV of < 5% for 25OHD2 and 25OHD3. The results of the accuracy test showed that the bias was below 6.19% in the absence of 3-epi 25OHD3. Comparison of the 25OHD results obtained by the two methods for 982 patients (age 1-100years) revealed excellent clinical agreement (Cohen's kappa=0.875) and correlation (R2=0.973). Among the 982patients, only 73patients had 3-epi 25OHD3 (>6.25nmol/L); out of these 73patients, the 3-epi 25OHD3 level in 58patients was between 6.25 and 12.5nmol/L. In patients with <375nmol/L 25OHD (25OHD2+25OHD3), only 8 had 3-epi 25OHD3 levels exceeding 12.5nmol/L (range: 13.3 - 27.5nmol/L). Among samples containing 3-epi 25OHD3, only three were separated into different 25OHD-deficiency groups using the above methods.
  
  
  CONCLUSIONS
  A rapid and precise EPI-LC-MS/MS method for measuring 25OHD with efficient separation of 3-epi 25OHD3 was developed. Our results showed that 3-epi 25OHD3 had little effect on the routinely used NEPI-LC-MS/MS.
authors.affiliation: Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China.
authors.forename: Songlin
authors.initials: S
authors.lastname: Yu
authors.affiliation: Beijing Hospital National Center for Clinical Laboratories, Ministry of Health, Beijing 100730, China.
authors.forename: Weiyan
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Department of Clinical Laboratory, China-Japan Friendship Hospital, Beijing 100029, China.
authors.forename: Ruiping
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China.
authors.forename: Xinqi
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China.
authors.forename: Huiling
authors.initials: H
authors.lastname: Fang
authors.affiliation: Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Han
authors.affiliation: Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Cheng
authors.affiliation: Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Su
authors.affiliation: Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China. Electronic address: lingqiubj@163.com.
authors.forename: Ling
authors.initials: L
authors.lastname: Qiu
mesh_terms: D002112:Calcifediol / Q000097:blood*; D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D057230:Limit of Detection; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D; D002112:Calcifediol
keywords: Liquid chromatography; Mass spectrometry; Vitamin D