Serial 6-month change in forced vital capacity predicts subsequent decline and mortality in Japanese patients with newly diagnosed idiopathic pulmonary fibrosis.

BACKGROUND

The clinical course of idiopathic pulmonary fibrosis (IPF) is characterized by a progressive decline in lung function; however, predicting changes in lung function is difficult. We sought to determine whether the prior 6-month trend in forced vital capacity (FVC) could predict mortality and the subsequent 6-month trend in FVC.

METHODS

We retrospectively analyzed consecutive patients with newly diagnosed IPF who underwent serial pulmonary function tests. The immediate two years after the initial evaluation were divided into four terms of six months each and stratified on the basis of presence or absence of a ≥10% relative decline in FVC at six months (declined and stable groups, respectively).

RESULTS

We included 107 patients with %predicted FVC of 80.8% and %predicted diffusing capacity of the lung for carbon monoxide of 58.9%. In multivariate analysis, a decline in %predicted FVC in the initial six months was found to be an independent prognostic factor (hazard ratio 4.45, 95% confidence interval 2.62-7.56, p < 0.01). Among the 46 terms in which the FVC declined during the initial 1.5-year study period, a decline in FVC was exhibited in 23 (50.0%) of the subsequent terms. Among 231 terms in which FVC remained stable, a decline was observed in 32 (13.9%) of the subsequent terms (relative risk 3.61, p < 0.01). The frequency of FVC decline in each term was 16-27%. FVC was stable or declined in all four terms in 50.5% and 15.9% of cases, respectively.

CONCLUSIONS

Six-month decline in FVC predicts subsequent FVC change and mortality in IPF patients in the era of antifibrotic agents.