Discord of prediction equations in assessment of exercise intolerance

<bold>Rationale:</bold> Peak oxygen uptake (<bold>VO_2Peak</bold>) reflects a person’s cardiopulmonary oxygen carrying capacity and assists in the clinical evaluation of their respiratory symptoms. The concordance of the different reference equations used for rating of exercise tolerance is unclear. <bold>Objective:</bold> To examine the impact of reference equation selection on classifying exercise tolerance. <bold>Methods:</bold> We examined VO_2Peak in 245 never-smokers with remote history of occupational secondhand smoke exposure (Zeng; BMJ Open Respir Res 2022). Predicted VO_2Peak were calculated using 5 reference equations; VO_2Peak <80 %predicted was used to define exercise intolerance. Agreement in exercise tolerance classifications was measured by Cohen’s Kappa, and the associations of VO_2Peak %predicted values with dyspnea score (by mMRC) were examined via logistic regression and ROC analysis. <bold>Results:</bold> %predicted VO_2Peak varied significantly as did the % of subjects with exercise intolerance (<bold>Table</bold>). The agreement between exercise intolerance classifications varied from moderate to near perfect (κ=0.51 to 0.83). There were significant reclassifications ranging from 6 to 22% in both directions combined, resulting from -35 to 70% change in VO_2Peak %predicted. The predicted VO_2Peak were associated with mMRC≥1 with the AUC ranging from 0.63 to 0.74. <bold>Discussion:</bold> Use of different reference equations sizably reclassifies exercise tolerance in both directions and affects the interpretation of symptoms. <fig><object-id>erj;64/suppl_68/PA2605/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>