Individuals with interstitial lung abnormality on chest CT scan should undergo regular CT scans at intervals of 3 years to monitor disease progression, suggests a recent study published in the American Journal of Respiratory and Critical Care Medicine.¹

This study included 305 patients with some findings related to interstitial lung abnormality on chest CT scans. Nonsmokers were also included in the study group. Through this study, the investigators aimed to determine the optimal interval of follow-up CT scans in these patients. The dates on which the initial CT was done along with CT scans showing disease progression were noted. The participants were followed for a median duration of 11.3 years.

Some interstitial lung abnormalities were detected, in minimum of one CT scan in 239 (78.4%) subjects out of the 305 participants included in the study.

Progression of the interstitial lung abnormality occurred in 80.5% of patients on serial follow-up CT scans. The median time for disease progression was 3.2 years. Around 17.3% patients progressed to progression to usual interstitial pneumonia in a median duration of 11.8 years.

Detection of fibrosis and its extent was independently associated with the risk of disease progression with hazard ratio (HR) of 1.12. It was also associated with the risk of progression to usual interstitial pneumonia with HR of 1.39.

There were marked differences in overall survival at 10 years when patients were categorized according to the presence of honeycombing and fibrosis affecting either 1% of the entire lung or 5% per lung zone. The incidence of adverse outcomes was higher in these patients.

Interstitial lung abnormalities are incidentally detected on CT scan. Ground-glass or reticular abnormality, traction bronchiectasis or bronchiolectasis, lung distortion, honeycombing and nonemphysematous cysts are the different interstitial lung abnormalities. These may advance to lung fibrosis with decline in lung function. Clinically significant interstitial lung disease should be excluded in these individuals. Interstitial lung abnormalities have been linked to risk of lung cancer and increased mortality. Hence, patients at risk of progression must be actively monitored at regular intervals.2

This study has identified the appropriate interval for follow-up CT scans in patients with  any interstitial lung abnormality . It suggests that these patients should undergo regular CT scans at intervals of 3 years to monitor disease progression. The authors however caution that the screening interval may be decreased for patients in whom the examination of CT scans shows honeycombing and large extent of fibrotic lung changes. This study also highlights multidisciplinary management of patients with ILA with a radiologist playing a pivotal role.

References

1. Sohee Park, et al. Long-term follow-up of interstitial lung abnormality: implication in follow-up strategy and risk thresholds. Am J Respir Crit Care Med. 2023 Oct 15;208(8):858-867. doi: 10.1164/rccm.202303-0410OC.
2. Hata A, et al. Interstitial lung abnormalities: state of the art. Radiology. 2021 Oct;301(1):19-34. doi: 10.1148/radiol.2021204367.