The use of oxygen at rest is associated with a greater likelihood of death or lung transplant in people with idiopathic pulmonary fibrosis (IPF), a study shows. The results also showed that lower lung function at the start of the study, as measured by tests like forced vital capacity (FVC), was predictive of a higher likelihood of transplant or death.
The study, titled “Predictors of death or lung transplant after a diagnosis of idiopathic pulmonary fibrosis: insights from the IPF-PRO Registry,” was published in the journal Respiratory Research.
Because IPF is a progressive disease, with a clinical course that varies from person to person, it is important for researchers and clinicians to be able to identify those patients at greater risk for more severe disease.
To learn more, researchers analyzed data from the Idiopathic Pulmonary Fibrosis Prospective Outcomes (IPF-PRO) registry (NCT01915511), which compiles detailed information on people with IPF to improve understanding of the natural history of the disease.
Importantly, the IPF-PRO registry has some distinct advantages as compared with other, similar studies that have aimed to identify predictors of disease progression in IPF.
The IPF-PRO registry includes data for patients from 14 different clinics in the U.S. Furthermore, unlike in clinical trials, there are no disease severity criteria limiting eligibility for inclusion in the IPF-PRO. The only major criterion is that a patient must be diagnosed with IPF within six months of enrollment in the registry.
This means that the results of analyzing data from this registry are likely to be more easily generalized than those of other studies.
In this study, researchers used statistical models to determine whether there were associations between various patient characteristics — including age, sex, and markers of lung function — and disease outcome.
As the primary endpoint, the team used death or lung transplant. The rationale for this combination is that patients who required a lung transplant likely had such severe disease that, in the absence of a transplant, they would have died. The researchers noted that there were not enough cases of lung transplant in the patient group analyzed to be used as an endpoint on its own.
Data from a total 662 participants were analyzed. Most (74.9%) of the patients were male, and most were or had been smokers (68.4%). In total, 111 patients died or had a lung transplant over a follow-up period of 30 months.
Around one in five (19.6%) were using supplemental oxygen at rest, and the researchers found that this was the strongest predictor of death or lung transplant. Use of oxygen during activity was also significantly associated with the probability of death or lung transplant.
“Notably,” the researchers said, “the association between oxygen use at rest and death or lung transplant was independent of many factors previously associated with disease progression,” such as predictors of lung function and hospitalization.
Lower FVC and carbon monoxide diffusing capacity of the lungs, which are two predictors of lung function, also were associated with a greater risk of death or transplant. In the broadest sense, these tests measure the ability of the lungs to do their job — bring in oxygen and then transfer it to the blood.
There also was a significant association between age and risk of death or transplant, but this association wasn’t linear. The results showed that, among those younger than age 62, older patients were less likely to die or need a transplant. However, after age 62, older patients were more likely to die or need a transplant.
Overall, “data from the IPF-PRO Registry demonstrated high mortality in patients with IPF, with oxygen use at rest being the strongest predictor of mortality over the follow-up period,” the researchers said.
Notably, these are only correlations, the investigators said. They noted that it’s hard to say, for example, whether being on oxygen actually exacerbates disease progression in some way, or whether patients with more severe disease are more likely to be placed on oxygen. However, in either event, the knowledge of these predictive features may allow clinicians and IPF patients to make better-informed decisions.
“Careful consideration of oxygen requirements in patients with newly diagnosed IPF is a powerful prognostic tool to inform physician and patient decision-making regarding clinical care and potential treatment options,” the team concluded.