Serum Krebs von den Lungen-6 concentrations reflect severity of anti-melanoma differentiation-associated protein 5 antibody positive dermatomyositis associated interstitial lung disease

Rapidly progressive interstitial lung disease (RP-ILD) is a major complication of anti-melanoma differentiation-associated protein 5 antibody positive dermatomyositis (anti-MDA5+DM) with a high mortality rate. The aim of the study is to determine whether serum Krebs von den Lungen-6 (KL-6) could be a prognostic biomarker to predict RP-ILD and prognosis in anti-MDA5+DM patients.A total of 21 anti-MDA5+DM patients with RP-ILD and 20 anti-MDA5+DM patients without RP-ILD were retrospectively included in this study. Serum KL-6 concentration (pg/mL) was measured using the latex agglutination test.Serum KL-6 level was higher in RP-ILD patients than those in non-RR-ILD patients (1195.61±872.93 vs. 452.6±465.51 pg/mL, p=0.002). The best cut-off value of KL-6 serum level was 500.9 pg/mL using ROC curve (AUC area = 0.7976, p=0.0011). KL-6 >500.9 pg/mL was an independent risk factor for RP-ILD using multivariate analysis (OR=56.38, 95% CI 5.51-577.504, p=0.001). Serum KL-6 concentrations were significantly higher in dead patients than those in the survivor group (1209.34±840.55 vs. 592.41±667.76, p=0.0033), and higher KL-6 concentration was also an independent risk factor for all-cause death after adjusting confounders (OR = 21.94, 95% CI 3.3-145.73, p=0.001). Anti-MDA5+DM patients with higher KL-6 level displayed a significantly decreased one-year survival rate, as compared with lower KL-6 level (36.36% vs. 89.47%, p=0.0008).The serum KL-6 levels reflect severity of lung injury and serve as a clinically useful biomarker in detection and monitoring RP-ILD progression in anti-MDA5+DM patients.