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.
CasasA, VilaroJ, RabinovichR, MayerA, BarberàJA, Rodriguez-RoisinR, RocaJ. Encouraged 6-min walking test indicates maximum sustainable exercise in COPD patients. Chest, 2005; 128(1):55–61.
2.
LeungAS, ChanKK, SykesK, ChanKS. Reliability, validity, and responsiveness of a 2-min walk test to assess exercise capacity of COPD patients. Chest, 2006; 130(1):119–125.
3.
CataneoDC, CataneoAJ. Accuracy of the stair climbing test using maximal oxygen uptake as the gold standard. J Bras Pneumol, 2007; 33(2):128–133.
4.
HollandAE, SpruitMA, TroostersT, PuhanMA, PepinV, SaeyD, et al. An Official European Respiratory Society/American Thoracic Society Technical Standard: field walking test in chronic respiratory disease. Eur Respir J, 2014; 44(6):1428–1446.
5.
CoteCG, Pinto-PlataV, KasprzykK, DordellyLJ, CelliBR. The 6-min walk distance, peak oxygen uptake, and mortality in COPD. Chest, 2007; 132(6):1778–1785.
6.
CasanovaC, CoteC, MarinJM, Pinto-PlataV, de TorresJP, Aguirre-JaímeA, et al. Distance and oxygen desaturation during the 6-min walk test as predictors of long-term mortality in patients with COPD. Chest, 2008; 134(4):746–752.
7.
HernandesNA, WoutersEF, MeijerK, AnnegarnJ, PittaF, SpruitMA. Reproducibility of 6-minute walking test in patients with COPD. Eur Respir J, 2011; 38(2):261–267.
8.
PittaF, TroostersT, SpruitMA, ProbstVS, DecramerM, GosselinkR. Characteristics of physical activities in daily life in chronic obstructive pulmonary disease. Am J Respir Crit Care Med, 2005; 171(9):972–977.
9.
DouradoVZ, TanniSE, ValeSA, FaganelloMM, SanchezFF, GodoyI. Systemic manifestations in chronic obstructive pulmonary disease. J Bras Pneumol, 2006; 32(2):161–171.
10.
SpruitMA, WoutersEF. New modalities of pulmonary rehabilitation in patients with chronic obstructive pulmonary disease. Sports Med, 2007; 37(6):501–518.
11.
GuyattGH, PugsleySO, SullivanMJ, ThompsonPJ, BermanL, JonesNL, FallenEL, TaylorDW. Effect of encouragement on walking test performance. Thorax, 1984; 39(11):818–822.
12.
LeachRM, DavidsonAC, ChinnS, TwortCH, CameronIR, BatemanNT. Portable liquid oxygen and exercise ability in severe respiratory disability. Thorax, 1992; 47(10):781–789.
13.
IriberriM, GáldizJB, GorostizaA, AnsolaP, JacaC. Comparison of the distances covered during 3 and 6 min walking test. Respir Med, 2002; 96(10):812–816.
14.
SciurbaF, CrinerGJ, LeeSM, MohsenifarZ, ShadeD, SlivkaW, WiseRA. Six-minute walk distance in chronic obstructive pulmonary disease: reproducibility and effect of walking course layout and length. Am J Respir Crit Care Med, 2003; 167(11):1522–1527.
15.
EiserN, WillsherD, DoréCJ. Reliability, repeatability and sensitivity to change of externally and self-paced walking tests in COPD patients. Respir Med, 2003; 97(4):407–414.
16.
ChatterjeeAB, RissmillerRW, MeadeK, PaladenechC, ConfortiJ, AdairNE, et al. Reproducibility of the 6-minute walk test for ambulatory oxygen prescription. Respiration, 2010; 79(2):121–127.
17.
StevensD, ElpernE, SharmaK, SzidonP, AnkinM, KestenS. Comparison of hallway and treadmill six-minute walk tests. Am J Respir Crit Care Med, 1999; 160(5 Pt 1):1540–1543.
18.
TroostersT, VilaroJ, RabinovichR, CasasA, BarberàJA, Rodriguez-RoisinR, RocaJ. Physiological responses to the 6-min walk test in patients with chronic obstructive pulmonary disease. Eur Respir J, 2002; 20(3):564–569.
19.
WuG, SandersonB, BittnerV. The 6-minute walk test: how important is the learning effect?. Am Heart J, 2003; 146(1):129–133.
20.
RodriguesSL, MendesHF, ViegasCAA. Six minute walk test: study of the effect of learning in chronic obstructive pulmonary disease patients. Rev Port Pneumol, 2004; 30(2):121–125.
21.
SpencerLM, AlisonJA, McKeoughZJ. Six-minute walk test as an outcome measure: are two six-minute walk tests necessary immediately after pulmonary rehabilitation and at three-month follow-up?. Am J Phys Med Rehabil, 2008; 87(3):224–228.
22.
PaltamaaJ, WestH. Reliability of physical functioning measures in ambulatory subjects with MS. Physiother Res Int, 2005; 10(2):93–109.
23.
ToomeyE, CooteS. Between-rater reliability of the 6-minute walk test, Berg balance scale and handheld dynamometry in people with multiple sclerosis. Int J MS Care, 2013; 15(1):1–6.
24.
Global Initiative for Chronic Obstructive Lung Disease. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease. Updated 2015. http://goldcopd.org/.
MillerMR, HankinsonJ, BrusascoV, BurgosF, CasaburiR, CoatesA, et al. ATS/ERS task force: standardisation of lung function testing. Eur Respir J, 2005; 26(2):319–338.
27.
PereiraCAC, SatoT, RodriguesSC. Novos valores de referência para espirometria forçada em brasileiros adultos de raça branca. J Bras Pneumol, 2007; 33(4):397–406.
28.
BorgGA. Psychophysical bases of perceived exertion. Med Sci Sports Exerc, 1982; 14(5):377–381.
29.
FleissJL. The design and analysis of clinical experiments. New York: John Wiley; 1986, pp. 1–32.
WaltonDM, MacdermidJC, NielsonW, TeasellRW, ChiassonM, BrownL. Reliability, standard error, and minimum detectable change of clinical pressure pain threshold testing in people with and without acute neck pain. J Orthop Sports Phys Ther, 2011; 41(9):644–650.
32.
WalterSD, EliasziwM, DonnerA. Sample size and optimal designs for reliability studies. Stat Med, 1998; 17(1):101–110.
33.
GuyattGH, SullivanMJ, ThompsonPJ, FallenEL, PugsleySO, TaylorDW, BermanLB. The 6-minute walk: a new measure of exercise capacity in patients with chronic heart failure. Can Med Assoc J, 1985; 132(8):919–923.
34.
AnderssonM, MobergL, SvantessonU, SundbomA, JohanssonH, EmtnerM. Measuring walking speed in COPD: test-retest reliability of the 30-metre walk test and comparison with the 6-minute walk test. Prim Care Respir J, 2011; 20(4):434–440.
35.
CahalinL, PappagianopoulosP, PrevostS, WainJ, GinnsL. The relationship of the 6-min walk test to maximal oxygen consumption in transplant candidates with end-stage lung disease. Chest, 1995; 108(2):452–459.
36.
ZieglerB, RovedderPME, OliveiraCL, de Abreu e SilvaF, de Tarso Roth DalcinP. Repeatability of the 6-minute walk test in adolescents and adults with cystic fibrosis. Respir Care, 2010; 55(8):1020–1025.
37.
PoulainM, DurandF, PalombaB, CeugnietF, DesplanJ, VarrayA, PréfautC. 6-minute walk testing is more sensitive than maximal incremental cycle testing for detecting oxygen desaturation in patients with COPD. Chest, 2003; 123(5):1401–1407.
38.
HollandAE, HillCJ, RasekabaT, LeeA, NaughtonMT, McDonaldCF. Updating the minimal important difference for six-minute walk distance in patients with chronic obstructive pulmonary disease. Arch Phys Med Rehabil, 2010; 91(2):221–225.
39.
PuhanMA, ChandraD, MosenifarZ, RiesA, MakeB, HanselNN, et al. The minimal important difference of exercise tests in severe COPD. Eur Respir J, 2011; 37(4):784–790.
40.
RedelmeierDA, BayoumiAM, GoldsteinRS, GuyattGH. Interpreting small differences in functional status: the six minute walk test in chronic lung disease patients. Am J Respir Crit Care Med, 1997; 155(4):1278–1282.
41.
RoomiJ, JohnsonMM, WatersK, YohannesA, HelmA, ConnollyMJ. Respiratory rehabilitation, exercise capacity and quality of life in chronic airways disease in old age. Age Ageing, 1996; 25(1):12–16.
42.
EatonT, YoungP, MilneD, WellsAU. Six-minute walk, maximal exercise tests: reproducibility in fibrotic interstitial pneumonia. Am J Respir Crit Care Med, 2005; 171(10):1150–1157.
