CHI3L1 and atrial fibrillation: Some of the AF proteins we identified in the present study (GPI, PTRN11, OLR1, ENO1, GAPDH, CHI3L1, CSF3, LCN2, PGLYRP1, LDHB, PRTN3, and SNAP25) have not been widely explored in previous studies; therefore, they could provide additional insight into the discovery of biomarkers for further understanding of the pathophysiologic pathways leading to preterm birth23.