Chest muscle area, spleen density, CD4 + T%, and C4 to predict the development of interstitial lung disease in patients with Sjögren's syndrome: a clinical prediction model.

objectiveTo explore the value of combining chest muscle measurements, spleen density, and immunological serum indicators for predicting the occurrence of interstitial lung disease (ILD) in Sjögren's syndrome (SS).

methodsA retrospective study was performed by SS patients admitted to the First Affiliated Hospital of Henan Medical University from January 2018 to June 2025 and 196 cases were included. Propensity score matching (PSM) was used to balance baseline characteristics, resulting in the Sjögren's syndrome without interstitial lung disease (SS-NILD, n = 59) and Sjögren's syndrome-associated interstitial lung disease (SS-ILD, n = 32) groups. Spearman correlation analysis was performed to assess variable relationships, and variance inflation factor (VIF) and tolerance (TOL) to quantify multicollinearity severity. Binary logistic regression was used to build models. The area under the receiver operating characteristic curve (AUC) was used to determine discriminatory ability and DeLong's test to compare different models. Finally, model performance was assessed through calibration curves, decision curve analysis (DCA), and Bootstrap internal validation, and the contribution of imaging indicators was analyzed.

resultsThe occurrence of SS-ILD was associated with reduced spleen density (SD), decreased total pectoral muscle area (T-PMA), decreased right pectoral muscle area (R-PMA), lower CD4⁺T lymphocyte percentage (CD4

conclusionModel 1 (T-PMA, SD, CD4⁺T%, and C4) demonstrates potential for the early prediction of SS-ILD and carries substantial clinical translational value. Key Points • Developed a SS-ILD predictive model using pectoral muscle area, spleen density, CD4⁺T cell percentage, and complement C4. • Built via correlation heatmap, collinearity diagnosis, and propensity score matching for bias control, the model includes more indicators than prior studies and has reliable internal validation. • Identified the association of pectoralis muscle cross-sectional area with SS-ILD, and potential links of systemic immune dysregulation, muscle atrophy, splenic involvement to SS-ILD pathogenesis. • Selected indicators are easily accessible, facilitating clinical application and validation.