Survival odds for interstitial pneumonia are better when the condition is comorbid with rheumatoid arthritis or systemic sclerosis than when the pulmonary fibrosis is idiopathic.
Strand MJ, Sprunger D, Cosgrove GP, et al., Pulmonary Function and Survival in Idiopathic vs Secondary Usual Interstitial Pneumonia.CHEST (2014) 146:775-785. doi: 10.1378/chest.13-2388.
Patients who have connective tissue disease (CTD) survive longer with interstitial pneumonia than those with idiopathic pulmonary fibrosis (IPF), according to new research, although declines in pulmonary function over time appear similar in both groups.
Researchers from the National Jewish Health center in Denver speculate that the worse outcome in IPF patients is due to a higher rate of fatal acute exacerbations of pulmonary fibrosis than among CTD patients with “usual” interstitial pneumonia.
In the study, IPF patients faced worse median long-term survival at 4.4 years compared with CTD patients who had usual interstitial pneumonia at 7.1 years. Follow-up for the study took place over a decade.
Sub-group analysis shows survival to be longer in patients with
rheumatoid arthritis and systemic sclerosis compared with IPF patients. The researchers saw no significant differences between IPF patients and those with undifferentiated connective tissue disease.
The authors note this is the first study that shows a longitudinal trajectory of respiratory function in patients with biopsy-proven usual interstitial pneumonia. (Usual interstitial pneumonia displays distinct patterns of lung injury that can be seen on biopsy.) However, they caution that the small numbers of CTD patients at a single center (321 with IPF and 56 with CTD) is a study limitation.
The two groups had no significant difference in the decline of forced vital capacity (FVC) or forcible breath exhalation during spirometry, either before diagnosis or 10 years after. The researchers also find no major between-group differences for the diffusing capacity of the lung for carbon monoxide (DLCO) over time.