Correlation of pulmonary function and usual interstitial pneumonia computed tomography patterns in idiopathic pulmonary fibrosis

•UIP CT pattern may represent spectrum of disease progression or unique IPF phenotypes.•Possible or atypical UIP CT patterns may represent early or less severe clinical disease.•FVC% correlated with extent of interstitial findings, but not CT pattern.•DLCO% correlated with both CT pattern and global interstitial findings.•After adjustment for a priori covariables, UIP CT pattern was not predictive of survival.

BackgroundLittle is known about presenting 'inconsistent' or 'possible' usual interstitial pneumonia (UIP) computed tomography (CT) patterns advancing to 'consistent' UIP as disease progresses in idiopathic pulmonary fibrosis (IPF). We hypothesized that if 'consistent' UIP represented more advanced disease, such a pattern on presentation should also correlate with more severe pulmonary function test (PFT) abnormalities.Material and methodsConsecutive IPF patients (2005-2013) diagnosed by international criteria with baseline PFT and CT were included. Presenting CTs were assessed by three expert radiologists for consensus UIP pattern ('consistent', 'possible', and 'inconsistent'). Approximation of individual and combined interstitial abnormalities was also performed with correlation of interstitial abnormalities and UIP CT pattern made with PFT findings and survival.ResultsThree-hundred and fifty patients (70% male) were included with a mean age of 68.3 years. Mean percent predicted forced vital capacity (FVC%) and diffusion capacity (DLCO%) was 64% and 45.5% respectively. Older age and male gender correlated more with 'consistent' UIP CT pattern. FVC% was not associated with any UIP pattern but did correlate with total volume of radiologist assessed interstitial abnormalities. DLCO% was lower in those with 'consistent' UIP pattern. A 'consistent' UIP CT pattern was also not independently predictive of survival after correction for age, gender, FVC%, and DLCO%.ConclusionPFT findings appear to correlate with extent of radiologic disease but not specific morphologic patterns. Whether such UIP patterns represent different stages of disease severity or radiologic progression is not supported by coinciding pulmonary function decline.