Among patients with chronic obstructive pulmonary disease (COPD), peak oxygen uptake was correlated significantly with the incremental shuttle walk test (ISWT) and almost as significantly with the 6-minute walk test (6MWT), according to study findings published recently in BMC Pulmonary Medicine.
Although cardiopulmonary exercise testing (CPET) is more precise than field testing for evaluating patients with COPD, CPET is cumbersome and expensive. In contrast, field tests — specifically, the 6MWT and the ISWT — evaluate functional exercise capacity, including prognosis and response to treatment, and are much simpler to administer. Peak oxygen uptake (peak VO2) measures cardiopulmonary capacity and has previously demonstrated a strong correlation with the distance of a field test. Researchers aimed to compare the correlations of the 2 walking test distances with peak VO2 in patients with COPD.
To accomplish this, they conducted a systematic review and meta-analysis of 12 studies found in MEDLINE, Scopus, Embase, and the Cochrane Library through June, 2020, comparing the correlation of peak VO2 with either the 6MWT or ISWT in COPD patients. These studies included 746 patients with sample sizes varying from 13 to 209 patients, with 10 studies reporting correlation between peak VO2 and 6MWT distance and 5 reporting correlation between peak VO2 and ISWT distance.
The studies revealed a significant correlation between peak VO2 and 6MWT and ISWT distances (6MWT: r = 0.65, 95% CI, 0.61–0.70; ISWT: r = 0.81, 95% CI, 0.74–0.85; P <.0001). The ISWT showed a lower heterogeneity than the 6MWT (6MWT: I2 = 56%; P =.02; ISWT: I2 = 0%; P =.71). Through subgroup analysis, researchers further found that both the 6MWT and ISWT had a higher correlation coefficient in the low exercise capacity group vs the high exercise capacity group.
Although prior studies have compared peak VO2 correlations with ISWT and 6MWT distances, the researchers said their study was the first to perform a meta-analysis of the correlation. They noted that their meta-analysis provided further evidence that 6MWT and ISWT correlated significantly with peak VO2 levels found through measurement via CPET in patients with COPD.
Although the ISWT distance demonstrated a better correlation than the 6MWT with peak VO2, the investigators stressed the need to use both tests, noting that “the strength of the relationship between peak VO2 and walking distance in the field tests was affected by the exercise capacity in COPD patients, suggesting the importance of using various exercise tests.”
Limitations of the meta-analysis and systematic review included the small number of studies examined, variations between studies for measuring peak VO2, and the lack of prospective studies.
Chae G, Ko EJ, Lee SW, et al. Stronger correlation of peak oxygen uptake with distance of incremental shuttle walk test than 6-min walk test in patients with COPD: A systematic review and meta-analysis. BMC Pulm Med. 2022;22(1):102. doi:10.1186/s12890-022-01897-0