SESSION TITLE: Hot Topics in COPD
SESSION TYPE: Original Investigation Slide
PRESENTED ON: Tuesday, October 27, 2015 at 11:00 AM - 12:15 PM
PURPOSE: A substantial fraction of smokers or ex-smokers with apparently normal spirometry show radiographic signs of emphysema and/or air trapping1. In the full COPDGene Phase1 cohort we determined if isolated abnormality of FEV3/FEV6 (V3V6) is an independent predictor of computed tomography (CT) abnormalities, exercise intolerance and poor quality of life.
METHODS: We used spirometry, quantitative CT and functional measures (6MWD and SGRQ). Those defined to have airflow obstruction by V3V6<lower limit of normal (LLN) equations2 were compared to V3V6≥LLN. General linear regression models were applied to explain the relation between spirometry, quantitative CT indices, patient-reported and functional outcomes on normality vs. abnormality of V3V6 after controlling for age, sex, race, smoking history, CT scanner type and BMI. Log transformation was used for outcomes; the estimated regression coefficients were back-transformed.
RESULTS: 7853 subjects (age 45-80 years) with CT and best blow spirometry data were available. Of the 4386 subjects who had pre-bronchodilator FEV1/FVC≥LLN, 15.4% had V3V6 <LLN. These latter subjects had higher median air trapping [10.8% (IQR25-75: 5.3-19.6) vs. 8.6% (IQR25-75: 4.0-15.1), p<0.0001], mean segmental wall area [61.4%±3.2 vs. 60.3%±3.0, p<0.0001], SGRQ total score [19.9 (IQR25-75: 6-38) vs. 10.4 (IQR25-75: 3-27), p<0.0001] and lower 6MWD [415±116 m vs. 444±108 m, p< 0.0001] than those with V3V6≥LLN. Regression models in the 7853 subjects revealed that subjects with evidence of airflow obstruction by V3V6<LLN had higher emphysema (β=3.27, CI%95:3.08-3.47, p<0.0001), air trapping (β=2.51, CI%95:2.41-2.62, p<0.0001), segmental wall area (β=1.038, CI%95:1.036-1.041, p<0.0001), SGRQ (β=2.36, CI%95:2.24-2.48, p<0.0001) and lower 6MWD (β=0.83, CI%95:0.82-0.85, p<0.0001) compared to subjects with V3V6≥LLN.
CONCLUSIONS: 15.4% of subjects with pre-bronchodilator FEV1/FVC ≥LLN have airflow obstruction by V3V6<LLN with poorer functional indices, quality of life and greater structural changes in CT.
CLINICAL IMPLICATIONS: In subjects whose FEV1/FVC is normal, low V3V6 is a marker for identifying subjects with mild impairment in quantitative CT, functional and patient-reported outcomes. Evaluation of V3V6 should be part of routine spirometry interpretation. Supported by NIH R01HL089856, R01HL089897. References: 1. Schroeder JD et al. Am J Roentgenol 2013; 201: 460-470. 2.Hansen J et al. J COPD F, in press.
DISCLOSURE: The following authors have nothing to disclose: Asli Gorek Dilektasli, Janos Porszasz, Richard Casaburi, William Stringer, Surya Bhatt, Youngju Pak, George Washko, Peter Castaldi, Raul Estepar, James E. Hansen
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