Targeted LC/MS-Based Quantitative Determination of 8 Endogenous Free Fatty Acids in Human Pleural Effusion Using Surrogate Analytes

Free fatty acids (FFA) such as oleic acid, docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) have recently been identified to be promising cancer biomarkers that can differentiate malignant from benign pleural effusion in the diagnosis of non-small cell lung cancer (NSCLC). However, untargeted metabolomic approaches often used during early stages of biomarker discovery do not permit direct comparison of data measured across multiple platforms and experiments. This limitation poses a challenge for further validation of these FFA biomarkers for the diagnosis of NSCLC. Here, we developed and validated a targeted liquid chromatography-mass spectrometry (LC/MS)-based method using surrogate analytes to simultaneously quantify the absolute concentrations of a panel of 8 endogenous FFAs in human pleural effusion. These FFAs include 3-hydroxypalmitic acid [FA16:0(3-OH)], oleic acid (FA18:1), linoleic acid (FA18:2), arachidonic acid (FA20:4), eicosapentaenoic acid (EPA, FA20:5), docosatetraenoic acid (FA22...