title: Validity of the six-minute step test of free cadence in patients with chronic obstructive pulmonary disease.
abstract: OBJECTIVE
  to evaluate the concurrent validity of the six-minute step test (6MST) in assessing exercise capacity of COPD patients using the six-minute walk test (6MWT) as a gold-standard. The predictive validity of the 6MST was assessed to determine a cut-off point for identification of low exercise capacity.
  
  
  METHODS
  thirty-two COPD patients (50-87 years old) with mild to very severe obstruction performed the 6MST and 6MWT twice.
  
  
  RESULTS
  Concurrent validity: a strong positive correlation (Pearson) between the number of ascents on the first (T1), second (T2) and the best of both (T1 or T2) tests during the 6MWT was observed. Although a moderate negative correlation with BODE index and FEV1 was found, it was considered insufficient to test the validity, therefore ROC curves were not applied. The predictive validity (ROC) of the 6MST to identify low physical capacity (compared with the 6MWT) using the performance of T1 or T2, or solely T1 was considered accurate, and the area under the curve was 0.8 (IC95% 0.62-0.98) and 0.85 (IC95% 0.70-0.99), respectively. To classify patients, the cut-off points of 86 and 78 steps were chosen, with both values showing 90% of sensitivity and specificity of 64% and 68% for T1 or T2, or solely T1, respectively.
  
  
  CONCLUSIONS
  The number of steps on the 6MST was valid to verify exercise capacity in COPD patients and the cut-off point of 78 steps was able to identify patients with poor exercise tolerance. Values under this cut-off point are considered to identify patients with a poorer prognosis.
authors.affiliation: Laboratory of Spirometry and Respiratory Therapy, Universidade Federal de São Carlos, São Carlos, SP, Brazil.
authors.forename: Bruna V
authors.initials: BV
authors.lastname: Pessoa
authors.affiliation: Laboratory of Spirometry and Respiratory Therapy, Universidade Federal de São Carlos, São Carlos, SP, Brazil.
authors.forename: Juliano F
authors.initials: JF
authors.lastname: Arcuri
authors.affiliation: Laboratory of Spirometry and Respiratory Therapy, Universidade Federal de São Carlos, São Carlos, SP, Brazil.
authors.forename: Ivana G
authors.initials: IG
authors.lastname: Labadessa
authors.affiliation: Laboratory of Spirometry and Respiratory Therapy, Universidade Federal de São Carlos, São Carlos, SP, Brazil.
authors.forename: Joyce N F
authors.initials: JN
authors.lastname: Costa
authors.affiliation: Laboratory of Spirometry and Respiratory Therapy, Universidade Federal de São Carlos, São Carlos, SP, Brazil.
authors.forename: Anna C
authors.initials: AC
authors.lastname: Sentanin
authors.affiliation: Laboratory of Spirometry and Respiratory Therapy, Universidade Federal de São Carlos, São Carlos, SP, Brazil.
authors.forename: Valéria A Pires
authors.initials: VA
authors.lastname: Di Lorenzo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005080:Exercise Test / Q000379:methods*; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000503:physiopathology*; D015203:Reproducibility of Results; D013997:Time Factors