Comparing the quantitation of specialized pro-resolving mediators in plasma and serum using ELISA and LC-MS/MS.

Quantitation of oxylipins is generally performed using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Researchers can also use commercial enzyme-linked immunosorbent assays (ELISAs), due to convenience or where access to instrumentation is limited. However, oxylipins are small molecules with many isomers and metabolites that are difficult to fully discriminate using ELISAs, with many potential sources of cross-reactivity. In this paper, the use of ELISAs for oxylipin analysis is compared with LC-MS/MS, with two specialized pro-resolving mediators (SPM) as examples. By reviewing the literature, we show that ELISAs report significantly higher levels of resolvin D1 (RvD1) and resolvin D2 (RvD2) than LC-MS/MS. Also, we show experimentally that in plasma and serum samples where these lipids were not detected using LC-MS/MS, a positive result could be obtained using ELISA, and that these signals increase with improper sample processing. In conclusion, while ELISA can be a valuable screening tool for the presence of oxylipins, positive signals need validation using LC-MS/MS.