Incidental radiologic evidence of interstitial lung disease and time to pulmonary evaluation

Background: Interstitial lung diseases (ILD) are relatively rare fibrotic lung diseases that can cause significant morbidity and mortality. Early diagnosis of ILDs is crucial to improve patient survival. Incidental radiologic findings of interstitial lung disease may provide an opportunity for early diagnosis. We sought to estimate the incidence of incidental interstitial lung disease findings on CT scans ordered for other reasons and quantify the time to pulmonary function test or pulmonary referral. Methods: In this retrospective cohort study performed at a large metropolitan health system, radiology reports from CT scans of the neck, chest, abdomen/pelvis, and coronary arteries of adult patients were reviewed for documentation of ILD findings based on the pre-defined search terms. We also descriptively examined time from CT scan to pulmonary function testing or pulmonology referral. The main outcomes were incidence of ILD findings on CT scans and frequency of follow up testing. Results: Of the 239,535 scans that were included, there were 25,219 initial scans with ILD findings (10.8%). Of those patients, only 16.1% had pulmonary function testing or pulmonary referral at one year, and 23.9% at 5 years. Follow up testing was more common if interstitial lung disease findings were present on CT chest compared to other scan types. The median time to PFT for all scan types was 59 days and the median time to pulmonary referral was 112 days. Conclusion: In conclusion, incidental findings of interstitial lung disease are common on many different types of CT scans but infrequently lead to follow up pulmonary function testing or referral to a pulmonary specialist. Significant delays in time were noted for pulmonary referrals. This study raises awareness of delay in diagnosing ILD.