Circulating concentrations of fibroblast activation protein α in apparently healthy individuals and patients with acute coronary syndrome as assessed by sandwich ELISA.

Abstract Background Fibroblast activation protein α (FAP) is a membrane glycoprotein with dipeptidyl-peptidase and collagenase activity and is expressed in cancer, arthritis, and atherosclerotic plaques. We hypothesized that FAP can be measured quantitatively in the circulation and provide prognostic information in acute coronary syndrome (ACS). Methods We assessed the performance of a commercially available FAP ELISA and the pre-analytic characteristics of the marker. We determined FAP concentrations in EDTA plasma samples from 101 apparently healthy blood donors and 407 patients with ACS. Patients were followed for 12months regarding all-cause mortality and non-fatal myocardial infarction (MI). Results FAP was stable at room temperature (for 1day) and 4°C (3days) and resistant to 3 freeze/thaw cycles. Recovery of recombinant human FAP ranged from 78 to 103% and serial dilutions of spiked samples resulted in measurements within 91 to 120% of expected values. Patients with ACS had lower plasma FAP concentrations compared with blood donors [median (25th–75th percentiles): 84 (69–101)ng/mL vs. 108 (87–124)ng/mL, P Conclusions Our study is the first to associate FAP with prognosis in ACS. The favorable pre-analytic characteristics of FAP will facilitate future studies of the marker in other disease settings associated with altered FAP expression.