Development and external validation of a model for lung transplantation-free survival prediction of primary Sjögren syndrome-associated interstitial lung disease: a prospective cohort study.

Background: Primary Sjögren syndrome-associated interstitial lung disease (pSS-ILD) patients have a worse prognosis than pSS patients without pulmonary involvement. This study aims to establish a prediction nomogram for early prediction of lung transplantation (LTx)-free survival in pSS-ILD patients. Methods: The training cohort comprised 260 patients from China-Japan Friendship Hospital between 1 January 2016 and 30 June 2022, while the external validation cohort consisted of 135 patients from Beijing Chaoyang Hospital between 1 January 2007 and 31 December 2012. Univariable Cox regression analysis and least absolute shrinkage and selection operator were employed for variable selection, and a nomogram model was developed to predict the 1-, 3- and 5-year LTx-free survival. Discrimination and calibration of the nomogram were assessed using the concordance index (C-index), area under the curve, calibration curve and decision curve analysis. Results: Multivariable Cox regression demonstrated that elevated age, oxygenation index, carbohydrate antigen 125 and fibrosis score were independent risk factors for LTx-free survival in pSS-ILD patients. The C-index values for the training and validation cohorts were 0.812 and 0.809, respectively. The 1-, 3- and 5-year AUC values for the training cohort were 0.781, 0.874 and 0.909, respectively, while those for the validation cohort were 0.793, 0.826 and 0.863. The bias-corrected curve was close to the ideal curve and revealed a strong consistency between predicted and observed outcomes. Conclusions: We developed a nomogram capable of predicting the LTx-free survival probability at 1, 3 and 5 years in pSS-ILD patients. This model has the potential to be a useful tool for prediction of death or LTx in pSS-ILD.