Ab1383 Predictors of Autoimmunity and Survival in New-Onset Interstitial Lung Disease: A Prospective Observational Cohort Study

Background: Connective tissue diseases (CTDs) and interstitial pneumonia with autoimmune features (IPAF) are the most common causes of interstitial lung disease (ILD) after idiopathic pulmonary fibrosis with potential treatment options. However, less is known regarding the natural history these entities particularly among patients with new-onset disease. Objectives: This study aims to identify the baseline predictors of autoimmunity and survival in a new-onset ILD cohort. Methods: Adult patients with a diagnosis of diffuse ILD within six months and no prior treatment were initially screened between June 2018 and June 2020. Exclusion criteria were known causes of ILD other than CTD and IPAF such as environmental/occupational exposure, hypersensitivity, sarcoidosis, radiotherapy, and presence/history of malignancy, chronic infections, and post-infectious pulmonary sequela. All patients had a baseline standard comprehensive clinical rheumatological assessment (CCRA), seroimmunological tests including two potential biomarkers, PTX3 and soluble CD163 (sCD163), and nailfold capillaroscopy (NFC) in addition to general evaluation of ILD including HRCT, pulmonary function tests, echocardiography, 6-min walk test, and basic laboratory. CCRA was repeated every three months. Data were analyzed after completion of a minimum observation period of 40 months. Thirty age-, sex-, and smoking-matched healthy controls were included in NFC and biomarker analyses. Results: Fifty-five patients were included in the study. Initially, 27 (49.1%), 14 (25.5%), and 14 (25.5%) had features compatible with idiopathic ILD (i-ILD), IPAF, and CTD (6 systemic sclerosis, 5 Sjögren's syndrome, 2 overlap syndromes, 1 dermatomyositis), respectively. After a median observation period of 54 (40-81) months, two (14.3%) out of 14 patients with baseline IPAF fulfilled classification criteria for rheumatoid arthritis-Sjögren's syndrome overlap and rheumatoid arthritis, 10 and 11 months after the diagnosis, respectively (Figure 1a). Baseline presence of any digital/serosal/cutaneous or two or more CCRA features and positive ANA test significantly favored a diagnosis of IPAF/CTD in multiple logistic regression (Table 1). Notably, 14 (51.9%) of patients in the i-ILD group had a NSIP pattern on HRCT and 14 (51.9%) had at least one CCRA feature, mostly caused by senile musculoskeletal (18.5%) and glandular (33.3%) symptoms. During follow-up, no patient in the i-ILD group had additional CCRA feature. Abnormal NFC findings were mostly due to systemic sclerosis patients and exclusion of those resulted in similar NFC findings across the study groups. Serum PTX3 was similar in ILD and healthy controls whereas sCD163 was slightly higher in ILD (126.3 44.8-857.9 vs 94.9 13.9-192.5 ng/mL, p=0.023). Systemic sclerosis patients had considerably higher sCD163 (298.8 102.4-857.9 ng/mL) (Figure 1b). Survival was not significantly different among groups (Figure 1c). Among higher age at diagnosis, lower baseline carbon monoxide diffusing capacity, and higher baseline echocardiographic systolic pulmonary artery pressure (sPAP), only sPAP remained significantly associated with survival time in multivariable Cox model. HR for death was 9.67 (2.16-43.30) in those with 35 mmHg or higher sPAP (Figure 1d). Conclusion: Most cases with CTD may be identifiable during initial assessment of new-onset ILD with a combination of a thorough clinical evaluation and ANA test. Baseline sPAP may predict short-term mortality. REFERENCES: NIL. Acknowledgements: The authors thank Turkish Society of Rheumatology for funding. Disclosure of Interests: None declared.