title: Changes in pulmonary function test results after 1 year of therapy as predictors of survival in patients with idiopathic pulmonary fibrosis.
abstract: The study group consisted of 58 patients with idiopathic pulmonary fibrosis (IPF) recognized between 1970 and 1991 who were treated for their pulmonary disease, survived for at least 1 year from the time of initiation of treatment, and had forced vital capacity (FVC) measurements at the time of diagnosis and 9 to 15 months later. Forty-four of the patients also had a single-breath diffusing capacity (Dsb) measured initially and after 9 to 15 months of treatment and 33 patients had an arterial blood gas, breathing room air at the time of diagnosis and 9 to 15 months into therapy. Patients' conditions were classified as improved, unchanged, or worse after the year of treatment based on each of the three pulmonary function tests. A > or = 10% increase in FVC, > or = 20% increase in Dsb, and > or = 5 mm Hg decrease in alveolar-arterial difference in oxygen partial pressure [P(A-a)O2] defined improved function. A > or = 10% decrease in FVC, > or = 20% decrease in Dsb, and > or = 5 mm Hg increase in P(A-a)O2 defined worse function. Patients with < 10% change in FVC, < 20% change in Dsb, and < 5 mm Hg change in P(A-a)O2 were regarded as having unchanged conditions. Kaplan-Meier survival plots and the Cox proportional hazard regression model were used to analyze survival time in relation to change in pulmonary function after 1 year of therapy. Patients with an improved or unchanged FVC at 1 year had no difference in survival (p = 0.75), but both showed enhanced survival compared with patients with a > or = 10% reduction in FVC with 1 year of treatment (p < 0.001). Patients with an improved or unchanged Dsb at 1 year also had no difference in survival (p = 0.21) but again, both showed enhanced survival compared with patients with > or = 20% decrease in Dsb with 1 year of treatment (p < 0.001). Changes in gas exchange after 1 year of treatment did not correlate with survival in the three groups. There was a trend for longer survival in improved patients compared with those with worsening gas exchange, but the p value was not significant at 0.17. We conclude that changes in the FVC and Dsb after 1 year of treatment are strongly predictive of duration of survival in patients with IPF.
authors.affiliation: Section of Pulmonary and Critical Care Medicine, Virginia Mason Medical Center, Seattle, WA 98111, USA.
authors.forename: D
authors.initials: D
authors.lastname: Hanson
authors.forename: R H
authors.initials: RH
authors.lastname: Winterbauer
authors.forename: S H
authors.initials: SH
authors.lastname: Kirtland
authors.forename: R
authors.initials: R
authors.lastname: Wu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016001:Confidence Intervals; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D011658:Pulmonary Fibrosis / Q000401:mortality* / Q000503:physiopathology*; D012129:Respiratory Function Tests / Q000706:statistics & numerical data; D016019:Survival Analysis; D013997:Time Factors; D014861:Washington / Q000453:epidemiology