Retrospective evaluation of the clinical impact of demographic, serological, clinical, radiological parameters and treatment modalities in patients with rheumatoid arthritis associated interstitial lung disease

Introduction and Objective: Interstitial lung disease involvement in rheumatoid arthritis (RA-ILD) is one of the most significant determinants of morbidity and mortality among RA patients. This study aims to evaluate the demographic and serological characteristics of RA-ILD patients followed in our clinic. And investigate the relationship with smoking, define the phenotypic features and severity of lung involvement using high-resolution computed tomography (HRCT), assess the efficacy of treatments administered in RA-ILD patients, and identify the parameters affecting mortality. Ultimately, we aim to contribute to improving the diagnostic and therapeutic processes of RA-ILD. Materials and Methods: In this retrospective study, we evaluated 65 patients with rheumatoid arthritis-associated interstitial lung disease (RA-ILD) who were followed in our clinic. The study involved individuals diagnosed with rheumatoid arthritis who showed interstitial changes on high-resolution computed tomography (HRCT) imaging. We collected data on demographics, clinical findings, laboratory results, pulmonary function tests, HRCT images, and treatments from the hospital information system patient records. We analyzed the relationships between disease progression, mortality, and factors such as age, gender, smoking history, serological test results, disease duration, HRCT findings, rheumatoid arthritis activity scores (DAS28-ESR), pulmonary function tests, and treatments. Results: The study included 65 patients, with a mean age of 67.14 ± 9.52 years. Among the participants, 60% were female and 40% were male. Of the total, 26.2% had died, with 58.8% of these deaths attributed to pulmonary causes. Patients who exhibited lung involvement exceeding 20% on HRCT scans had a significantly higher mortality rate. Regarding smoking habits, 47.5% of participants were non-smokers, while 27.9% had a smoking history of more than 30 pack-years. Serological evaluations showed high positivity rates for rheumatoid factor (RF) at 60% and anti-citrullinated protein antibodies (ACPA) at 71.4%. The mean duration between diagnoses of rheumatoid arthritis (RA) and interstitial lung disease (ILD) was 7.82 ± 10.16 years. The most common HRCT pattern observed was usual interstitial pneumonia (UIP), present in 46.2% of patients, while 32.3% had lung involvement exceeding 20% on HRCT. At the time of ILD diagnosis, 33.3% of patients were in remission, which increased to 71.9% at the final follow-up. The proportion of patients exhibiting high disease activity decreased from 3.5% initially to none at the last evaluation. Additionally, forced vital capacity (FVC) and diffusing capacity of the lungs for carbon monoxide (DLCO) values declined over time, with the final mean DLCO value recorded at 56.69 ± 21.68. In terms of treatment, 90.8% of patients received methotrexate (MTX), 75.4% received hydroxychloroquine (HCQ), and 56.9% received rituximab (RTX). Notably, the rate of RTX administration was significantly higher in patients with the UIP pattern. However, no significant relationship was found between the treatment agents and mortality. Conclusion: Our study findings align with the literature, indicating that RA-ILD is more common in older patients, males, seropositive individuals, and those with a smoking history. RA-ILD mortality is higher compared to non-ILD RA patients. Among ILD phenotypes, UIP is the most frequently observed pattern, with higher lung involvement percentages in this group. As lung involvement increases, pulmonary function declines, and mortality rises. Consistent with previous studies, no correlation was found between seropositivity, DAS28 score, and ILD phenotype. However, although numerically significant, the finding that patients with high-titer seropositivity may have more extensive lung disease was not statistically significant. In deceased patients, pulmonary function test results were lower, disease activity was higher, and the interval between RA and ILD diagnoses was shorter. Patients with high disease activity at RA diagnosis had lower FVC values at ILD diagnosis, while those in remission had higher FVC values. Patients with UIP and NSIP patterns exhibited greater declines in pulmonary function, with UIP associated with higher mortality; however, these findings were not statistically significant but aligned with existing literature. Unlike similar studies, no significant decline in FVC and DLCO values was observed with increased smoking history. Furthermore, in contrast to previous research, no statistically significant relationship was found between TNFi agents (or any treatment agent) and mortality. Prior studies have reported conflicting findings regarding the effects of seropositivity on pulmonary function tests and the impact of seropositivity and smoking on mortality. Our study did not identify a significant correlation in these areas. Keywords: Rheumatoid arthritis, Interstitial lung disease, Smoking, DAS28, Seropositive, Seronegative, FVC, DLCO, HRCT, UIP, DMARD, Mortality