The minimal important difference in the 6-minute walk test for patients with pulmonary arterial hypertension

Stephen C. Mathai, Milo A. Puhan, Diana Lam, Robert A. Wise

Research output: Contribution to journalArticle

Abstract

Rationale: Although commonly used as the primary outcome measure of clinical trials in pulmonary arterial hypertension (PAH), the minimal important difference (MID) of the 6-minute walk test (6MWT) has not been well defined for this population of patients. Objectives: To estimate the MID in the 6MWT in patients with PAH. Methods: Study subjects from the clinical trial of tadalafil in PAH, a 16-week, parallel-group, randomized clinical trial of patients who were treatment naive or on background therapy with an endothelin receptor antagonist, were eligible. 6MWT was performed using a standardized protocol. Distributional and anchor-based methods were used to estimate the MID; the latter method used the Physical Component Summary Score (PCS) of the Medical Outcomes Study 36-item short form (SF-36). Measurements and Main Results: Four hundred five subjects were analyzed. Domains of the SF-36 were weakly to modestly associated with 6MWT. Change in the PCS of the SF-36 was most strongly associated with change in 6MWT (r = 0.40, P < 0.001) and thus was selected as the anchor for subsequent anchor-based analyses. Distributional analyses yielded estimates of the MID ranging from 25.1 to 38.5 m, whereas anchor-based analyses yielded an estimate of 38.6 m. Conclusions: Using both distributional and anchor-based methods, the estimated consensus MID in the 6MWT for PAH is approximately 33 m. These results have important implications for (1) assessing treatment responses from clinical trials and metaanalyses of specific PAH therapy, and (2) sample size calculations for future study design.

Original languageEnglish (US)
Pages (from-to)428-433
Number of pages6
JournalAmerican journal of respiratory and critical care medicine
Volume186
Issue number5
DOIs
StatePublished - Sep 1 2012

Keywords

  • 6-minute walk test
  • Minimal important difference
  • Outcome measures
  • Pulmonary hypertension

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Critical Care and Intensive Care Medicine

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