Comparison of different reference values for lung function, and implications of inconsistent use nationwide

Abstract

<b>Background:</b> For interpretation of pulmonary function tests (PFTs), reference values based on sex, age, height and ethnicity are needed. In Norway, the older ECSC reference equations remain widely used, and only half of the hospitals have implemented the recommended GLI reference values. <b>Objective:</b> To assess the effects of changing from ECSC to GLI reference values for spirometry and DLCO, using a cohort of adults with a broad range in age and lung function. <b>Methods:</b> PFTs from 458 adults (57% females, 18-85 years) included in recent clinical studies were used for comparing ECSC and GLI reference values for FVC, FEV1 and DLCO; % predicted and LLN were calculated. Bland-Altman plots and one-sample t-test were used to compare ECSC and GLI equations. <b>Results:</b> GLI predicted values were lower for FVC and FEV1, but higher for DLCO in both genders (fig). The disagreement was most pronounced in women, with mean (SD) difference 11(4) and 14(5) percent points for FVC and DLCO, respectively (p&lt;0.001 for both). DLCO was below LLN among 32% women when assessed with GLI, as compared with 54% when assessed with ECSC. <b>Conclusion:</b> The substantial observed differences between GLI and ECSC reference values are likely to entail consequences with respect to diagnostic and treatment criteria, inclusion in clinical studies and health care benefits. To ensure equity in care, GLI reference values should be consistently implemented.