Researchers at the University of British Columbia in Canada recently reported that mortality prediction models used in patients with idiopathic pulmonary fibrosis (IPF) can also be employed to assess short-term mortality in patients with systemic sclerosis-associated interstitial lung disease (SSc-ILD). The study was recently published in the Chest Journal and is entitled “Predicting mortality in systemic sclerosis-associated interstitial lung disease using risk prediction models derived in idiopathic pulmonary fibrosis.”
Mortality risk prediction tools have been developed for IPF, a progressive fatal lung disease in which the alveoli and the lung tissue are damaged, becoming thick and scarred (fibrotic tissue), leading to severe breathing difficulties and compromising oxygen transfer between the lungs and the bloodstream. IPF has a poor prognosis and around two-thirds of patients die within five years after being diagnosed.
In this study, researchers assessed whether IPF prediction models of mortality could also be applied in SSc-ILD. SSc is a rare, chronic autoimmune disease in which the body’s own immune system attacks healthy tissues, resulting in a hardening and tightening of the skin and connective tissues. The disease usually affects the skin, but it can also affect internal organs such as the lungs. In fact, SSc is associated to a high risk for ILD, a group of diseases that cause progressive scarring of lung tissue compromising the respiratory function and blood oxygenation.
Researchers analyzed 156 SSc-ILD patients with four baseline risk prediction models usually applied in the assessment of mortality in IPF patients – the du Bois index, the modified du Bois index, the ILD-GAP Index and the Composite Physiologic Index (CPI). In total, data on 1,294 pulmonary function tests, 725 6-minute walk tests and 637 echocardiograms was collected. One-year mortality rates were estimated using the four models.
The team found that the median survival rate was 15 years after SSc-ILD diagnosis, and that each model accurately predicted SSc-ILD patients’ one-year mortality. Among the models, the modified du Bois index was found to exhibit the best discrimination and an acceptable calibration. In addition, forced vital capacity and the 6-minute walk test were found to be important independent predictors of one-year mortality in SSc-ILD patients.
“We show that the modified du Bois index has good discrimination and calibration for the prediction of 1-year mortality in [systemic sclerosis-associated interstitial lung disease (SSc-ILD)], and that discrimination is also acceptable for the [Composite Physiologic Index (CPI)], [interstitial lung disease-gender, age, physiology (ILD-GAP)] and original du Bois index,” wrote the study’s lead author Dr. Christopher J. Ryerson and colleagues, according to a news release.
“Additional studies are required to determine how to translate these models into specific mortality estimates in SSc-ILD and how these estimates should then be used in clinical practice,” concluded the research team. “Future studies are also needed to determine whether novel mortality risk prediction tools can substantially improve prognostication in patients with SSc-ILD.”