Abstract
Current guidelines recommend separate spirometry reference equations for whites, African Americans, and Mexican Americans, but the justification for this recommendation is controversial. The authors examined the statistical justification for race/ethnic-specific reference equations in adults in the Third National Health and Nutrition Examination Survey (1988-1994) and the Multi-Ethnic Study of Atherosclerosis Lung Study (2000-2006). Spirometry was measured following American Thoracic Society guidelines. "Statistical justification" was defined as the presence of effect modification by race/ethnicity among never-smoking participants without respiratory disease or symptoms and was tested with interaction terms for race/ethnicity (× age and height) in regression models. There was no evidence of effect modification by race/ethnicity for forced expiratory volume in 1 second, forced vital capacity, or the forced expiratory volume in 1 second/forced vital capacity ratio among white, African-American, and Mexican-American men or women on an additive scale or a log scale. Interaction terms for race/ethnicity explained less than 1% of variability in lung function. The mean lung function for a given age, gender, and height was the same for whites and Mexican Americans but was lower for African Americans. Findings were similar in the Multi-Ethnic Study of Atherosclerosis Lung Study. The associations of age and height with lung function are similar across the 3 major US race/ethnic groups. Multiethnic rather than race/ethnic-specific spirometry reference equations are applicable for the US population.