Inflammatory activity as a predictor of clinical deterioration in interstitial pneumonia with autoimmune features: a...

Interstitial pneumonia with autoimmune features (IPAF) represents a heterogeneous entity overlapping with connective tissue disease-associated interstitial lung disease (CTD-ILD); however, its clinical course and prognostic determinants remain incompletely characterized.

This study aimed to compare baseline characteristics, outcomes, and predictors of poor prognosis between IPAF and CTD-ILD, and to evaluate the prognostic performance of selected inflammatory indices.

This study was designed as a single-center, retrospective cohort analysis evaluating clinical characteristics, radiological features, and prognostic outcomes in patients with interstitial lung disease.

This retrospective cohort study included 88 patients with ILD, categorized as IPAF (n = 30) or CTD-ILD (n = 58), including systemic sclerosis, rheumatoid arthritis, and Sjögren's disease-associated ILD. Baseline demographic, clinical, radiological, and laboratory data were systematically analyzed. Poor prognosis was defined as the occurrence of at least one of the following during follow-up: >10% decline in forced vital capacity (FVC), development of a radiological progression, or the need for treatment escalation. Univariable and multivariable logistic regression analyses were performed to identify predictors of poor prognosis. Discriminative performance of the Gender-Age-Physiology (GAP) score, Lung Immune Prognostic Index (LIPI), and derived neutrophil-to-lymphocyte ratio (dNLR) was evaluated using receiver operating characteristic (ROC) curve analysis.

Patients with IPAF were older at diagnosis compared with CTD-ILD (median 68.5 vs 56.0 years, p < 0.001), while female predominance was higher in CTD-ILD (81.0% vs 56.7%, p = 0.029). The GAP score was higher in IPAF, whereas anti-CCP positivity was more common in CTD-ILD. Despite these differences, clinical outcomes were comparable between groups, with no significant differences in FVC decline, development of radiological progression, treatment escalation, antifibrotic initiation, or composite poor prognosis. In univariable analysis, an increased persistent erythrocyte sedimentation rate (ESR) and C-reactive protein were associated with poor prognosis. In multivariable analysis, persistent ESR elevation remained an independent predictor (OR 3.25, 95% CI 1.15-9.23, p = 0.027). ROC analysis showed limited discriminative performance (AUC < 0.60) for GAP, LIPI, and dNLR.

Although IPAF and CTD-ILD differ in baseline phenotype, their clinical trajectories appear similar. Persistent systemic inflammation, reflected by sustained ESR elevation, independently predicts adverse outcomes, while commonly used prognostic scores demonstrate limited utility.