The YKL-40 protein is a potential biomarker for COPD: a meta-analysis and systematic review

Background: Many studies have found that YKL-40 may play an important pathogenic role in COPD. However, the results of these studies were inconsistent. Therefore, we performed a systematic review and meta-analysis to investigate the role of YKL-40 in COPD. Methods: We performed a systematic literature search in many database and commercial internet search engines to identify studies involving the role of YKL-40 in patients with COPD. The standardized mean difference (SMD) and Fisher's Z-value with its 95% confidence interval (CI) were used to investigate the effect sizes. Results: A total of 15 eligible articles including 16 case-control/cohort groups were included in the meta-analysis. The results indicated that the serum YKL-40 levels in patients with COPD were significantly higher than those in healthy controls (SMD=1.58, 95% CI=0.68-2.49, P=0.001), and it was correlated with lung function (pooled r=-0.32; Z=-0.33; P<0.001). The results of subgroup analysis found that the serum YKL-40 levels were statistically different between the exacerbation group and the stable group in patients with COPD (SMD=1.55, 95% CI=0.81-2.30, P=0.001). Moreover, the results indicated that the sputum YKL-40 levels in patients with COPD were also significantly higher than those in healthy controls (SMD=0.70, 95% CI=0.10-1.30, P=0.022). Conclusion: The current study suggests that YKL-40 may be implicated in bronchial inflammation and remodeling in COPD and may be considered as a useful biomarker for COPD diagnosis and monitoring.