Glycoprotein YKL-40: A novel biomarker of chronic graftvs- host disease activity and severity?

Aim To investigate whether increased YKL-40 levels positively correlate with graft-vs-host disease (cGVHD) activity and severity and if YKL-40 could serve as a disease biomarker. Methods This case-control study was conducted at the University Hospital Centre Zagreb from July 2013 to October 2015. 56 patients treated with hematopoietic stem cell transplantation (HSCT) were included: 35 patients with cGVHD and 21 without cGVHD. There was no difference between groups in age, sex, median time from transplant to study enrollment, intensity of conditioning, type of donor, or source of stem cells. Blood samples were collected at study enrollment and YKL-40 levels were measured with ELISA. Disease activity was estimated using Clinician's Impression of Activity and Intensity of Immunosuppression scales and disease severity using Global National Institutes of Health (NIH) score. Results YKL-40 levels were significantly higher in cGVHD patients than in controls (P = 0.003). The difference remained significant when patients with myelofibrosis were excluded from the analysis (P = 0.017). YKL-40 level significantly positively correlated with disease severity (P < 0.001; correlation coefficient 0.455), and activity estimated using Clinician's Impression of Activity (P = 0.016; correlation coefficient 0.412) but not using Intensity of Immunosuppression (P = 0.085; correlation coefficient 0.296). Conclusion YKL-40 could be considered a biomarker of cGVHD severity and activity. However, validation in a larger group of patients is warranted, as well as longitudinal testing of YKL-40 levels in patients at risk of developing cGVHD.