Screening for rheumatoid arthritis-associated interstitial lung disease using low-dose CT: an emerging approach — an observational prospective case-control study

Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is a major contributor to rheumatoid arthritis (RA) related morbidity and mortality. Early detection is challenging due to subclinical onset and limitations of conventional screening modalities. This study evaluated the diagnostic performance of low-dose photon-counting detector CT (LD PCD-CT) for RA-ILD and assessed its prevalence and risk factors in a Hungarian RA cohort. In this prospective study (Feb 2022–June 2023), 492 consecutively enrolled RA patients without known ILD, underwent LD PCD-CT, digital chest radiography (DR) and pulmonary function testing (PFTs). Imaging was scored using a standardized LD severity scale. Clinical, demographic, and serological data were analyzed to identify ILD predictors. Statistical analyses included Kolmogorov–Smirnov, t-tests, Mann–Whitney U, chi-squared/Fisher’s exact tests, Pearson correlation, and ROC analysis. Logistic regression was used to identify independent risk factors. LD PCD-CT identified interstitial abnormalities in 35% of patients. By contrast, clinical assessment and PFTs detected abnormalities in only 44% and 22% of these cases, respectively. Among patients without CT-defined abnormalities, 42% had a positive clinical assessment and 23% had abnormal PFTs, indicating limited diagnostic specificity. The most frequent findings were interstitial reticular abnormalities (58%) and usual interstitial pneumonia (22%). Independent ILD predictors included age ≥ 50 years, male sex, ≥ 25 pack-year smoking history, rheumatoid factor (RF) positivity, and elevated lactate dehydrogenase (LDH) levels. LD PCD-CT had a mean effective radiation dose of 0.415 mSv, remaining within low-dose diagnostic thresholds. LD PCD-CT demonstrated superior sensitivity and specificity for early RA-ILD detection compared to clinical assessment and PFTs, while maintaining low radiation exposure. Incorporating LD PCD-CT into risk-stratified screening protocols may facilitate earlier diagnosis and timely therapeutic interventions, ultimately improving patient outcomes. NCT05391100.