Elevated plasma YKL-40 as a prognostic indicator in patients with idiopathic pulmonary arterial hypertension

Background and objective Pulmonary vascular remodelling and inflammation have been implicated in pulmonary arterial hypertension (PAH). YKL-40, a marker of tissue remodelling and inflammation, has recently been recognized as a risk predictor of cardiovascular and inflammatory diseases. The study aimed to investigate a potential role of YKL-40 in predicting prognosis in idiopathic PAH (IPAH). Methods Plasma YKL-40 levels were measured in 82 IPAH patients without current or previous PAH-specific treatment during right heart catheterization and in 54 healthy volunteers. Concurrent data included clinical, haemodynamic and biochemical variables. Results Plasma YKL-40 levels were increased in IPAH patients compared with control subjects (median, interquartile range: IPAH: 24.90, 17.68-39.78 ng/mL; controls: 16.58, 14.20-19.64 ng/mL; P < 0.001). YKL-40 levels correlated with cardiac index (r = -0.244, P = 0.027) and N-terminal pro-brain natriuretic peptide (NT-proBNP, r = 0.263, P = 0.017). After a median follow-up of 578 days, YKL-40 outperformed NT-proBNP, uric acid, and 6-min walk distance in receiver operating characteristic (ROC) analyses in predicting both clinical worsening (area under the curve (AUC) 0.681) and death (AUC 0.717). Compared with patients with YKL-40 below the ROC-derived cut-off point (24.5 ng/mL), the high YKL-40 group showed higher pulmonary vascular resistance and serum uric acid levels, and showed more clinical worsening events and deaths in Kaplan-Meier analyses. Plasma YKL-40 was independently associated with clinical worsening in univariate and multivariate Cox analyses (all P < 0.05). Conclusions Plasma YKL-40 might serve as a promising indicator of disease severity and prognosis in patients with IPAH.