ILD-GAP combined with the Charlson Comorbidity Index score (ILD-GAPC) as a prognostic prediction model in patients with idiopathic pulmonary fibrosis, idiopathic nonspecific interstitial pneumonia, and collagen vascular disease-related interstitial pneumonia

Background: The ILD-GAP scoring system has been widely used to predict the prognosis of patients with interstitial lung disease (ILD). The ability of the ILD-GAP scoring system combined with the Charlson Comorbidity Index score (CCIS) (ILD-GAPC) to predict ILD prognosis was investigated. Methods: In ILD patients including idiopathic pulmonary fibrosis (IPF), idiopathic nonspecific interstitial pneumonia (iNSIP), and collagen vascular disease-related interstitial pneumonia (CVD-IP) treated between April 2013 and April 2017, the relationships between baseline clinical parameters including age, sex, CCIS, ILD diagnosis, pulmonary function test results, and 3-year ILD-related events, including cause-specific death and first acute exacerbation (AE), were retrospectively assessed, and the ability to predict prognosis was compared between ILD-GAP and ILD-GAPC. Results: A total of 174 patients (mean age, 74 years), all of whom underwent pulmonary function testing including percentage predicted diffusion capacity for carbon monoxide, were assessed. ILD diagnosis consisted of IPF in 57 cases, iNSIP, and CVD-IP in 117 cases. ILD-GAPC provided a greater area under the 3-year time dependent receiver operating characteristic curve (0.743) for predicting 3-year ILD-related events than ILD-GAP (0.710). In addition, log-rank tests showed that survival curves differed significantly among low, middle, and high ILD-GAPC scores (P = 0.003), unlike ILD-GAP scores (P = 0.240). Conclusions: ILD-GAPC could provide more accurate information for predicting prognosis in patients with ILD than ILD-GAP alone.