Potential of Krebs von den Lungen-6 as a predictor of relapse in interstitial pneumonia with anti-aminoacyl tRNA synthetase antibodies-positive dermatomyositis

Objective: To identify a predictor of relapse in interstitial pneumonia (IP) in patients with anti-aminoacyl tRNA synthetase antibodies-positive dermatomyositis (ARS-DMIP).

Methods: This retrospective cohort study comprised 27 ARS-DMIP patients. We compared clinical and laboratory findings between the relapse and non-relapse groups during 2 years after treatment initiation to find predictors of relapse in IP. Candidate predictors were further assessed by analysing the relationship with the relapse of IP.

Results: One patient with ARS-DMIP died. About 7 (26.9%) of the remaining 26 patients with ARS-DMIP had a relapse of IP. We found that the levels of serum Krebs von den Lungen-6 (KL-6) in the relapse group were significantly higher than those in the non-relapse group at the time points before treatment (P = .046) and after treatments, including 6 (P = .004), 12 (P = .013), 18 (P = .003) and 24 months (P < .001). The KL-6 values that maximised the area under the ROC curve were 2347 U/mL before treatment, 622 U/mL after 6 months and 468 U/mL after 12 months. The relapse rates after 104 weeks were significantly higher in patients with KL-6 levels ≥2400 U/mL before treatment (P = .014), ≥600 ng/mL after 6 months (P < .005) and ≥470 U/mL after 12 months (P = .010).

Conclusion: These findings suggest that the levels of KL-6 before and after treatment in ARS-DMIP may represent the disease activity of IP, and they may be useful as the predictor of relapse in IP in patients with ARS-DMIP.