The composite physiologic index (CPI) was derived to represent the extent of
fibrosis on high-resolution computed tomography (HRCT), adjusting for emphysema in patients
with idiopathic pulmonary fibrosis (IPF). We hypothesised that longitudinal change in CPI would
better predict mortality than forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) or
diffusing capacity of the lung for carbon monoxide (DLCO) in all patients with IPF, and especially
in those with combined pulmonary fibrosis and emphysema (CPFE).
Cox proportional hazard models were performed on pulmonary function data from IPF patients at
baseline (n=321), 6 months (n=211) and 12 months (n=144). Presence of CPFE was determined by
HRCT.
A five-point increase in CPI over 12 months predicted subsequent mortality (HR 2.1, p=0.004). At
12 months, a 10% relative decline in FVC, a 15% relative decline in DLCO or an absolute increase in
CPI of five points all discriminated median survival by 2.1 to 2.2 yrs versus patients with lesser
change. Half our cohort had CPFE. In patients with moderate/severe emphysema, only a 10%
decline in FEV1 predicted mortality (HR 3.7, p=0.046).
In IPF, a five-point increase in CPI over 12 months predicts mortality similarly to relative
declines of 10% in FVC or 15% in DLCO. For CPFE patients, change in FEV1 was the best predictor
of mortality.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91949/1/2011 ERJ - Pulmonary function measures predict mortality differently in IPF versus combined pulmonary fibrosis and emphysema.pd
