Validation of the MCK model for predicting outcomes in myopathy-associated interstitial lung disease: A multicentre MYKO cohort study

OBJECTIVES: To validate the MCK model's prognostic utility in patients with idiopathic inflammatory myopathy (IIM)-associated interstitial lung disease (ILD). METHODS: This retrospective study included 242 patients with IIM-associated ILD from the multicentre MYKO cohort. Patients were classified as anti-melanoma differentiation-associated gene 5 (MDA5) antibody-positive or antibody-negative. The MCK score was defined by the number of criteria met: C-reactive protein (CRP) ≥ 0.8 mg/dL and Krebs von den Lungen 6 (KL-6) ≥ 1000 U/ml for MDA5-positive patients; CRP ≥ 1.1 mg/dL and KL-6 ≥ 1000 U/ml for MDA5-negative patients. Outcomes included all-cause mortality, disease flares, and infections requiring hospitalisation, which were assessed via Kaplan-Meier and Cox regression analyses. RESULTS: Amongst MDA5-positive patients, an MCK score of 2 did not significantly predict mortality. However, in MDA5-negative patients, an MCK score of 2 was significantly associated with an increased risk of all-cause mortality, disease flares, and infections requiring hospitalisation. Subgroup analyses from 2018 onward showed similar patterns, although statistical significance was not maintained. CONCLUSIONS: The MCK model demonstrates strong predictive performance for all-cause mortality and disease complications, particularly in patients with MDA5-negative IIM. However, its predictive utility may have declined in recent years, possibly due to advancements in treatment approaches.