title: Idiopathic pulmonary fibrosis: a composite physiologic index derived from disease extent observed by computed tomography.
abstract: In idiopathic pulmonary fibrosis, the quantitation of disease severity using pulmonary function tests is often confounded by emphysema. We have identified the composite physiologic index (CPI) most closely reflecting the morphologic extent of pulmonary fibrosis. Consecutive patients with a clinical/computed tomography (CT) diagnosis of idiopathic pulmonary fibrosis (n = 212) were divided into group I (n = 106) and group II (n = 106). The CPI was derived in group I (by fitting pulmonary function tests against disease extent on CT) and was tested in Group II. The formula for the CPI was as follows: extent of disease on CT = 91.0 - (0.65 x percent predicted diffusing capacity for carbon monoxide [DLCO]) - (0.53 x percent predicted FVC) + (0.34 x percent predicted FEV1). In group II, the CPI correlated more strongly with disease extent on CT (r2 = 0.51) than the individual pulmonary function test (DLCO the highest value, r2 = 0.38). A subanalysis demonstrated that the better fit of the CPI was ascribable to a correction of the confounding effects of emphysema. Mortality was predicted more accurately by the CPI than by a pulmonary function test in all clinical subgroups, including a separate cohort of 36 patients with histologically proven usual interstitial pneumonia (CPI, p < 0.0005; FVC, p = 0.002; PO2, p = 0.002). In conclusion, a new CPI, derived against CT and validated using split sample testing, is a more accurate prognostic determinant in usual interstitial pneumonia than an individual pulmonary function test.
authors.affiliation: Department of Radiology, Royal Brompton Hospital, Interstitial Lung Disease Unit, Emmanuel Kaye Building, Manresa Road, Chelsea, London SW6 LR6, UK. a.wells@rbh.nthames.nhs.uk
authors.forename: Athol U
authors.initials: AU
authors.lastname: Wells
authors.forename: Sujal R
authors.initials: SR
authors.lastname: Desai
authors.forename: Michael B
authors.initials: MB
authors.lastname: Rubens
authors.forename: Nicole S L
authors.initials: NS
authors.lastname: Goh
authors.forename: Derek
authors.initials: D
authors.lastname: Cramer
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Nicholson
authors.forename: Thomas V
authors.initials: TV
authors.lastname: Colby
authors.forename: Roland M
authors.initials: RM
authors.lastname: du Bois
authors.forename: David M
authors.initials: DM
authors.lastname: Hansell
mesh_terms: D000368:Aged; D001706:Biopsy; D002248:Carbon Monoxide / Q000378:metabolism; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008168:Lung / Q000473:pathology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011237:Predictive Value of Tests; D011379:Prognosis; D011653:Pulmonary Diffusing Capacity; D011656:Pulmonary Emphysema / Q000175:diagnosis / Q000209:etiology / Q000401:mortality; D011658:Pulmonary Fibrosis / Q000175:diagnosis / Q000209:etiology* / Q000401:mortality; D013223:Statistics as Topic; D016019:Survival Analysis; D014057:Tomography, X-Ray Computed; D014109:Total Lung Capacity; D014797:Vital Capacity / Q000502:physiology
chemical_list: D002248:Carbon Monoxide