Isoprostanes (IsoPs) are radical-mediated byproducts of lipid peroxidation and are widely regarde as the "gold standard" for assessment of oxidative stress in vivo, and multiple studies have shown that normalized values for urinary Isoprostanes correlate very well with plasma values. 

ANALYICAL METHODS: Initially, an IsoP isomer (15F2tIsoP, previously called 8-iso-PGF2α) was analyzed by GC/MS.  Subsequently, LC/MS and immunoassay methods for quantificaion of 15F2tIsoP were reported.  AQlthough results obtained for GC/MS and Oxford's immunoassay show a strong correlation, the former was found to detect 4 isomers sith the same m/z ratio, whereas immunoassays likely detecy 15F2tIsoP as well as some 15F2tIsoP metabolites. 

IsoP METABOLISM:  It is known that 15F2tIsoP is rapidly metabolized by multiple pathways in humans.  In addition to Β-oxidation, a significant quantity (ranging from 20 to 80% depending on the expression of UDP-glucuronyl transferases in a given individual) of 15F2tIsoP is converted to glucuronides.  Given this wide range in metabolism, it is actually surprising that the levels of free urinary 15F2tIsoP correlate well with those in blood

URINARY ISOPROSTANE IMMUNOASSAY METHODS: Immunoassays can be performed quickly and inexpensively AND can be quantitative IF performed properly.  Recent publications have confirmed that Oxford's 15F2tIsoP immunoassay correlates well with results obtained by Gc/MS.  The following table gives the key features of the Oxford 15F2tIsoP method.

References available (please ask)

1. Smith K A, Shepherd J, Wakil A and Kilpatrick E S.  A comparison of methods for the measurement of 8-isoPGF2α: a marker of oxidative stress. Ann Clin Biochem March 2011, 48:147-154 2011

2. Soffler C, Campbell V L, Hassel D M. Measurement of urinary F2 isoparostanes as markers of in vivo lipid peroxidation: a comparison of enzyme immunoassays with gas chromatography-mass spectrometry in domestic animal species.  J Vet Diagn Invest. 2010 Mar; 22 (2) : 200-9.