Should the 6-Minute Walk Test Be Compared When Conducted by 2 Different Assessors in Subjects With COPD?
BACKGROUND
The 6-min walk test (6MWT) is an important tool in the assessment of functional capacity and prognosis in patients with COPD. However, especially in long-term follow-up in clinical settings, this test may be executed by a different assessor, and it is not well known whether 6MWT has an acceptable inter-rater reliability. The aim of this study is to analyze the intra- and inter-rater reliability of the performance in 6MWT, its cardiorespiratory changes, and effort perception in subjects with COPD.


METHODS
Thirty-two subjects with a diagnosis of COPD participated in the study, but 3 subjects did not appear on the second day of evaluation and therefore were included only in the intra-rater analysis; the first and second tests were executed by the same assessor with a 30-min interval between them, and the last was executed by a different assessor a week later. The intra-rater reliability was verified comparing the first and second 6MWT performance, and the inter-rater reliability was verified comparing the third test with the best performance of the first and second tests.


RESULTS
The intraclass correlation coefficient values were >0.75 (P < .001) for the walked distance on the 6MWT; however, the limits of agreement, SE of measurement, and minimal detectable difference were higher than the minimum clinically important differences already mentioned in the literature (∼25, 26, and 54 m), and the coefficient of variation was small in both intra- and inter-rater comparisons.


CONCLUSIONS
The 6MWT showed excellent reliability for distance and perceived exertion and moderate to excellent for HR and SD as assessed by intra- and inter-rater analysis. Thus, based on the main study outcomes, we concluded that the 6MWT can be compared when conducted by 2 different evaluators.
Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil. ivanaresp@ufscar.br.
Ivana G
IG
Labadessa
Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil.
Juliano F
JF
Arcuri
Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil.
Anna Cláudia
AC
Sentanin
Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil.
Joyce Nf
JN
da Costa
Universidade do Sagrado Coração, Bauru, São Paulo, Brazil.
Bruna V
BV
Pessoa
Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil.
Valéria Amorim Pires
VA
Di Lorenzo
D000368:Aged; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D015203:Reproducibility of Results; D013997:Time Factors; D000070857:Walk Test / Q000379:methods / Q000706:statistics & numerical data*
COPD; exercise test; reliability; walking