Is the six-minute step test able to reflect the severity and symptoms based on cat score?

This is the first study to investigate the performance of 6MST in COPD patients divided into different symptom severity groups based on the CAT questionnaire score.

To evaluate the relationship between the degree symptomatology using the chronic obstructive pulmonary disease (COPD) Assessment Test (CAT) with the six- minute step test (6MST) in COPD patients.

This is a cross-sectional study in which 59 patients with COPD were evaluated. The groups were stratified according to the subsequent cutoff points: CAT <10 (little impact) n= 22; CAT 11-20 (moderate impact) n=20; CAT <20 (large impact) n=17. During 6MST the individuals were instructed to go up and down a single step with a height of 20 centimeters (cm).

Comparing the groups in relation to performance on the 6MST, the number of climbs on the step were significantly higher in the CAT group <10 when compared to the CAT group >20, the variation in HR between rest and peak exercise (∆ HRpeak- rest) was lower in the CAT>20 group compared to the CAT<10 group and the CAT 11- 20 group. We found direct relationships between the number of ascents and descents in the 6MST vs the CAT score (r=0.35, p=0.007); and 6MST vs degree of obstruction of %FEV1 (r-0.46, p=0.002) We verified a linear regression model in which the FEV1 (L) and the CAT score influenced 29% in the performance of the 6MST.

The COPD severity represented by the FEV₁ and the CAT score are associated and influenced by 29% the performance of 6-minute step test. Our findings may have important implications for the clinical evaluation of these patients as well as for rehabilitation.