A response bias exists away from Borg Category-Ratio 0-10 scale values without associated verbal descriptors for symptom intensity ratings during cardiopulmonary exercise testing

Borg’s modified Category-Ratio 0-10 (CR10) scale is a 12-point scale with verbal descriptors (e.g., 5=severe, 7=very severe, 9=very, very severe) at each numerical rating other than 6 and 8. A cohort study of 1,048 people with malignant and non-malignant disease reported a lower-than-expected frequency of Borg CR10 ratings of 6 and 8 when breathlessness intensity was assessed at rest (Eur Resp J, 2016, 47:1861). We explored whether a response bias exists away from Borg CR10 ratings 6 and 8 for breathlessness and leg discomfort at peak exercise. We included 1,190 adults aged ≥40 years that completed symptom-limited incremental CPET on a cycle ergometer as part of the Canadian Cohort Obstructive Lung Disease study. A Poisson distribution was applied to determine the expected vs. observed rating frequency for each value on the Borg CR10 scale at peak exercise for breathlessness and leg discomfort. The observed frequency for Borg CR10 rating 6 was lower than expected for breathlessness and leg discomfort (n=61 vs. 180; n=67 vs. 193, p<0.001), as well as for rating 8 for leg discomfort (n=74 vs. 137, p<0.001) but not breathlessness (n=90 vs. 92, p=0.527). The observed frequencies were not different from expected for Borg CR10 ratings ≤5 (all p>0.05). In conclusion, a response bias away from Borg CR10 scale values of 6 and 8 without verbal descriptions exists for intensity ratings of breathlessness and leg discomfort at the symptom-limited peak of CPET in older adults.