Annual variation rate of KL-6 for predicting acute exacerbation in patients with rheumatoid arthritis-associated interstitial lung disease
Nozomi Tanaka, Keisuke Nishimura, Daisuke Waki, Keiichiro Kadoba, Hiroyuki Murabe, Toshihiko Yokota
Abstract
Abstract Objectives This study evaluated the prognostic factors for acute exacerbation (AE), including sequential changes in Krebs von den Lungen-6 (KL-6) levels, in rheumatoid arthritis-associated interstitial lung disease (RA-ILD) patients. Methods This was a retrospective observational study. We reviewed 125 patients diagnosed with RA-ILD between 2010 and 2019. We defined ΔKL-6 as the annual variation rate of KL-6 one visit before AE onset (or the last visit). The Cox regression analysis was used for evaluating significant variables associated with AE. We analysed the overall survival and respiratory-related death-free survival. Results Thirty-three patients (26.4%) developed AE during the observation period. The univariate analysis revealed that KL-6 levels at RA-ILD diagnosis [hazard ratio (HR), 1.11; 95% confidence interval (CI), 1.05–1.15; p < .01) and ΔKL-6 (HR: 3.69; 95% CI: −1.36 to 7.96; p = .01] were significantly associated with AE. ΔKL-6 was an independent prognostic factor for AE in the multivariate analysis (HR: 3.37; 95% CI: −1.16 to 8.87; p = .03). Patients with AE had a significantly higher overall mortality rate (p = .02) and respiratory-related mortality rate (p < .01) than those without AE. Conclusion ΔKL-6 can be a prognostic marker for detecting AE in RA-ILD patients.