B102-06 Diagnosis of Chronic Obstructive Pulmonary Disease: Correction Factor for Obesity

Introduction The diagnosis of chronic obstructive pulmonary disease (COPD) by spirometric criteria is confounded by the effects of obesity on the FEV1/FVC ratio, resulting in potential underdiagnosis of COPD in obese individuals. We aimed to develop correction factors for FEV1/FVC in overweight and obese adults with COPD. Methods We developed BMI-specific correction factors for FEV1/FVC using data from healthy non-smoking subjects aged ≥40 years in the National Health and Nutrition Examination Survey (NHANES) 2007-2012 (N = 2,658). After excluding a small number of individuals who were underweight (n = 16), subjects were stratified into four BMI categories based on standard obesity classifications: normal (18.5-24.9 kg/m²), overweight (25.0-29.9 kg/m²), obese (30.0-34.9 kg/m²), and severely obese (≥35.0 kg/m²). Within each BMI stratum, we employed the Lambda-Mu-Sigma (LMS) method using the Box-Cox Cole and Green distribution to estimate distributional parameters that account for skewness (L), central tendency (M), and coefficient of variation (S) of FEV1/FVC ratios. Correction factors were calculated as the ratio of each BMI category’s adjusted value to that of the reference normal BMI group. These BMI-specific correction factors were applied to the COPDGene cohort of current and former smokers (N = 10,132) by dividing observed FEV1/FVC by the corresponding correction factor. COPD classification was then reassessed using both the original FEV1/FVC <0.70 criterion and the BMI-corrected values to evaluate the impact of this adjustment on disease classification and subsequent clinical outcomes. Results The resulting correction factors for each BMI category were: 1.00 for Normal weight, 1.01 for Overweight, 1.02 for Obesity, and 1.04 for Severe Obesity. Application of the correction factors to COPDGene resulted in 338 (7%) participants newly meeting COPD criteria. On multivariable analyses, compared to participants without COPD, newly labelled participants had greater all-cause mortality (adjusted hazards ratio =1.26, 95%CI 0.99-1.61), more exacerbations (incidence rate ratio =1.07, 95%CI 0.87-1.34), worse quality of life (higher St. George’s Respiratory Questionnaire score =3.5, 95%CI 1.4-5.6), greater dyspnea (higher modified Medical Research Council score =1.2, 95%CI 1.1-1.3), and lower 6-minute walk distance (-12 m, 95%CI -24 to -0.8). Conclusions Application of a correction factor based on weight category resulted in a significant increase in the detection of COPD. This abstract is funded by: NHLBI R01 HL151421.