Disease behaviour classification: a pragmatic model for predicting outcomes in interstitial lung disease

Background and objective: The interstitial lung diseases (ILD) are a heterogenous group of disorders with similar clinical presentation, but widely varying prognoses. The use of a pragmatic disease behaviour classification (DBC), first proposed in international guidelines in 2013, categorises diseases into five behavioural classes based on their predicted clinical course. This study aimed to determine the prognostic utility of the DBC in an ILD cohort. Methods: Consecutive patients presented at the weekly multidisciplinary meeting (MDM) of a specialist ILD centre were included. MDM consensus was obtained for diagnosis and DBC category (1–5). Baseline and serial clinical and physiological data were collected over the study period (median 3.9 years, range 0–5.4 years). The relationship between DBC and prognostic outcomes was explored. Results: 137 ILD patients, [64 (47%) female] were included with mean age 67.0 ± 1.1 years, baseline FVC% 72.7 ± 1.7, and baseline DLco% 57.8 ± 1.6%. Patients were stratified into DBC by consensus at MDM: DBC1 n = 0 (0%), DBC2 n = 16 (12%), DBC3 n = 10 (7.3%), DBC4 n = 55 (40%), and DBC5 n = 56 (41%). On univariable Cox regression, increasing DBC class was associated with poorer progression-free survival (HR 1.6, 95% CI 1.2–2.0, p < 0.001). On multivariable Cox regression, DBC remained predictive of PFS when combined with age and gender (HR 1.4, 95% CI 1.1–1.9, p = 0.011), baseline FVC% (HR 1.5, 95% CI 1.1–1.8, p = 0.003) and ILD diagnosis (HR 1.6, 95% CI 1.2–2.2, p < 0.0001). Conclusion: DBC as determined at ILD multidisciplinary meeting may be a useful prognostic tool for the management of ILD patients.