NEW UK data suggest that baseline lung comorbidities may significantly influence the risk of developing interstitial lung disease (ILD) in patients with rheumatoid arthritis (RA), but only when assessed using disease-specific tools.
In a retrospective analysis examined two large, multicentre RA inception cohorts comprising 2,701 patients with a median follow-up of six years. The study aimed to clarify whether comorbidity burden contributes to ILD development in RA, and whether the method used to measure comorbidities affects risk prediction.
ILD in RA: A Serious Complication
Among the cohort, 101 patients (3.7%) were diagnosed with ILD. Twelve cases were identified at baseline, 46 developed during follow-up, and 43 were identified through death certification. ILD remains one of the most serious extra-articular complications of RA, associated with increased morbidity and mortality.
Multivariable analyses confirmed established risk factors for ILD, including older age at RA onset, seropositivity, and a history of smoking. However, the role of comorbidities depended on how they were quantified.
Disease-Specific Index Reveals Stronger Associations
When comorbidity burden was assessed using the Rheumatic Disease Comorbidity Index (RDCI), higher scores were significantly associated with ILD development. In particular, the lung disease component of the RDCI showed a strong independent association with subsequent ILD. The full RDCI score was also linked to increased risk.
In contrast, when comorbidity burden was measured using generic tools such as the Charlson Comorbidity Index or simple counts of major comorbidities, the association with ILD did not persist after adjustment.
These findings suggest that disease-specific comorbidity tools may better capture clinically relevant risk factors in RA than broader indices developed for general populations.
Implications for Risk Stratification
The authors conclude that baseline lung comorbidities should be considered alongside traditional risk factors such as age, smoking status, and autoantibody positivity when assessing ILD risk in RA.
Importantly, the study highlights that methodological choices in measuring comorbidity burden can directly influence risk prediction. Incorporating rheumatology-specific indices into routine assessment may help identify patients who would benefit from closer pulmonary monitoring or earlier screening.
While observational in nature, the analysis reinforces the need for targeted risk stratification strategies in RA, particularly given the potentially severe consequences of ILD.
