Systemic sclerosis associated interstitial lung disease: a conceptual framework for subclinical, clinical and progressive disease

OBJECTIVES: Establish a framework by which experts define disease subsets in systemic sclerosis associated interstitial lung disease (SSc-ILD).

METHODS: A conceptual framework for subclinical, clinical, and progressive ILD was provided to eighty-three experts, asking them to use the framework and classify actual SSc-ILD patients. Each patient profile was designed to be classified by at least 4 experts in terms of severity and risk of progression at baseline; progression was based on 1-year follow-up data. A consensus was reached if ≥ 75% of experts agreed. Experts provided information on which items were important in determining classification.

RESULTS: Forty-four experts (53%) completed the survey. Consensus was achieved on the dimensions of severity (75%, 60 of 80 profiles), risk of progression (71%, 57 of 80 profiles) and progressive ILD (60%, 24 of 40 profiles). For profiles achieving consensus, most were classified as clinical ILD (92%), low risk (54%), and stable (71%). Severity and disease progression overlapped in terms of framework items that were most influential in classifying patients (forced vital capacity, extent of lung involvement on high resolution chest CT (HRCT)); risk of progression was influenced primarily by disease duration.

CONCLUSIONS: Using our proposed conceptual framework, international experts were able to achieve a consensus on classifying SSc-ILD patients along the dimensions of disease severity, risk of progression, and progression over time. Experts rely on similar items when classifying disease severity and progression: a combination of spirometry and gas exchange and quantitative HRCT.