title: Quantification of urinary 8-iso-PGF2alpha using liquid chromatography-tandem mass spectrometry and association with elevated troponin levels.
abstract: OBJECTIVE
  Increased lipid peroxidation (i.e. "oxidative stress") has been identified as a central mechanism in the development of atherosclerosis and inflammatory vascular damage. Measurement of 8-iso-PGF(2alpha) has demonstrated to be a reliable indicator of in vivo oxidative stress levels. The purpose of this study was to develop a rapid, sensitive, and specific LC-MS/MS method for detection of urinary 8-iso-PGF(2alpha), establish reference intervals, and correlate isoprostane levels with cardiac troponin I.
  
  
  METHODS
  Urinary 8-iso-PGF(2alpha) was detected after direct injection onto a C18 silica column and monitored in the MRM mode using m/z transitions of 353.2>193.25 (8-iso-PGF(2alpha)) and 357.2>197.25 (8-iso-PGF(2alpha)-d(4)). The LC-MS/MS method was also compared to an ELISA kit. Reference interval studies were evaluated against a separate population of patients presenting with chest pain that had positive cTnI values.
  
  
  RESULTS
  Elution of 8-iso-PGF(2alpha) was achieved after 7 min, with a total run time of 10 min. Inter-assay CVs were 13.8-20.0% and intra-assay CVs were 10.9-17.0%. Linearity ranged from 100 pg/mL to 100 ng/mL. Deming regression of ELISA and LC-MS/MS methods for 8-iso-PGF(2alpha) levels yielded poor correlation, with a slope of 0.0265, y-intercept of 0.255 ng/mL, and R(2) value of 0.0434. Urine 8-iso-PGF(2alpha) concentrations in samples obtained from healthy individuals (n=34) ranged from 57 to 390 ng/g creatinine with a mean of 221 ng/g creatinine. 8-iso-PGF(2alpha) levels were statistically significant in troponin-positive (n=35) versus troponin-negative (n=36) patients (p<0.0049).
  
  
  CONCLUSIONS
  This LC-MS/MS method provides a rapid, accurate, sensitive, and cost-effective alternative to other methods for detection of 8-iso-PGF(2alpha) in urine. 8-iso-PGF(2alpha) has potential to be a great prognostic risk indicator in individuals with a high probability for future coronary events.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA. saenger.amy@mayo.edu
authors.forename: Amy K
authors.initials: AK
authors.lastname: Saenger
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Laha
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Edenfield
authors.forename: Sayed M H
authors.initials: SM
authors.lastname: Sadrzadeh
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods*; D003404:Creatinine / Q000032:analysis; D015237:Dinoprost / Q000031:analogs & derivatives* / Q000652:urine; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D015227:Lipid Peroxidation; D018384:Oxidative Stress; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014336:Troponin / Q000032:analysis*
chemical_list: D014336:Troponin; C075750:8-epi-prostaglandin F2alpha; D003404:Creatinine; D015237:Dinoprost