Acute exacerbation of idiopathic interstitial pneumonias (AE-IIPs) induces permanent pulmonary dysfunction and is potentially lethal. The unpredictable occurrence of AE-IIPs remains an important clinical issue in the management of IIPs.

In this multicentre, retrospective, observational study, a predictive score for AE-IIPs was designed using clinical factors based on multivariate Fine–Gray analysis in patients with IIPs.

Based on multivariate Fine–Gray analysis in an exploratory cohort of 487 patients with IIPs, the predictive score for AE-IIPs was determined as follows: 1 point each was added for honeycombing on high-resolution computed tomography (H), age >75 years (A) and lactate dehydrogenase level >222 U·L^-1 (L); the total score ranged from 0 to 3 (HAL score). The HAL score discriminated the risk of AE-IIPs with a C-index of 0.62 (95% CI 0.56–0.67); this discrimination was verified in a validation cohort of 402 patients with IIPs with a C-index of 0.67 (95% CI 0.60–0.73). In a combined cohort, the estimated cumulative risks for AE-IIPs at 1, 2, 3, 5 and 10 years were 1.9%, 3.5%, 5.1%, 7.7% and 12.9%, respectively, in the total score 0 group; 4.7%, 8.3%, 12.0%, 17.7% and 28.4%, respectively, in the total score 1 group; and 8.0%, 14.2%, 19.7%, 28.7% and 43.0%, respectively, in the total score =2 group. Subgroup analysis revealed that the HAL score was applicable to patients with and without idiopathic pulmonary fibrosis.

The HAL score discriminated the risk of AE-IIPs and could aid in the management of IIPs.