Ab1370 Interstitial Pneumonia With Autoimmune Feature: Demographic, Laboratory, and Clinical Aspects; Single Center Experience

Background: The European Respiratory Society and the American Thoracic Society (ERS/ATS) defined the term "interstitial pneumonia with autoimmune features (IPAF)" in 2015 for patients who have interstitial lung disease (ILD) but are not classified into any type of connective tissue diseases (CTD), despite having suggestive findings of CTDs. The IPAF classification is based on the morphological characteristics of lung parenchyma, as well as clinical and serological features 1. Objectives: The primary goal of this study was to define the demographic, clinical and serological features of patients who were classified as IPAF, and to investigate the survival and the progression of the condition into a confirmed CTD. Methods: A retrospective review was conducted on the records of 366 patients with ILD who had been diagnosed by a rheumatologist between 2011 and 2022. Patients who fulfilled the IPAF classification criteria were included in final analyses. The demographic and serological information of the patients, therapy regimens administered, pulmonary function tests, and the duration of follow-up periods were noted. The chest tomography (chest-CT) images were reassessed by three radiologists who were blinded to the patients' clinical and serological data. Results: Of 366 ILD patients, 81 patients met the IPAF criteria. The mean age at IPAF diagnosis was 61.4 ± 10.9 years, and 63% were female. 58% of the patients were never smokers. The most common symptom was dyspnea (90.1%), followed by cough (82.7%) and chest pain (18.5%). The most prevalent in serology was a positive antinuclear antibodies (ANA) test in 40% of the cases. The second most prevalent finding was the presence of rheumatoid factor (RF). Nonspecific interstitial pneumonia (NSIP) was the most frequent involvement pattern (83.9%). NSIP did not show a significant relationship with any serological markers and clinical findings when compared to organizing pneumonia (Table 1). After median of 15 (52) months of follow-up, a mortality rate was approximately 34%. The incidence of diabetes mellitus at the time of IPAF diagnosis was greater in the group that experienced mortality during the follow-up period (p=0.046). The average forced vital capacity (FVC) at baseline was significantly higher in the surviving group (p=0.038) (Table 2). Four patients fulfilled the criteria of a CTD during their follow-up. Conclusion: In this study, we found that majority of the patients were female and were ≥60 years old at the diagnosis. Similar to previous studies, NSIP was the most common pattern in our study group 4-5. An association was detected between a low baseline at the time of IPAF diagnosis and overall mortality. This factor could be crucial in determining the selection of aggressive therapeutic interventions for these patients. REFERENCES: 1 Fischer A, et al.. Eur Respir J. 2015 Oct;46(4):976-87. DOI: 10.1183/13993003.00150-2015. 2 Oldham JM, et al.. Eur Respir J. 2016 Jun;47(6):1767-75. DOI: 10.1183/13993003.01565-2015. 3 Karampeli M, et al. Mediterr J Rheumatol. 2020 Sep 30;31(3):330-336. DOI:10.31138/mjr.31.3.330. 4 Ahmad K et al. Respir Med. (2017) 123:56–62. 10.1016/j.rmed.2016.10.017. 5 Sambataro G et al. Respir Med. (2019) 150:154–60.10.1016/j.rmed.2019.03.011. Acknowledgements: NIL. Disclosure of Interests: None declared.