F2-isoprostanes have been advocated as a specific and reliable marker of oxidative damage (1) despite a lack of data on their biological and analytical variation. Concurrent with a longitudinal study of oxidative stress during the menstrual cycle [the BioCycle Study(2)], we have characterized the components of biological and analytical variation of free plasma F2-isoprostanes in the context of the menstrual cycle. We describe several of the key characteristics of F2-isoprostanes as a biomarker. Samples were collected from 9 healthy volunteers who met the major inclusion criteria of being a premenopausal woman 18–44 years of age and having regular menstrual cycles. Major exclusion criteria included use of hormonal preparations or contraceptive devices, pregnancy, a history of gynecologic abnormalities, recent infectious disease, routine intake of prescription and over-the-counter medications (including vitamin and mineral supplements), and a history of certain chronic diseases or conditions. Fasting blood samples were collected between 0700 and 0830 on days 2, 7, 12, 13, 14, 18, 22, and 27 of a single menstrual cycle. Collection and handling protocols were designed to minimize preanalytical variation. Samples were frozen at −80 °C and then analyzed, in duplicate, as a single set of consecutive samples by GC-MS (1) at the Molecular Epidemiology and Biomarker Research Laboratory at …
