Stronger Correlation of Peak Oxygen Uptake With Distance of Incremental Shuttle Walk Test Than 6-minute Walk Test in Patients With COPD: a Systematic Review and Meta-analysis

Background: The 6-minute walk test (6MWT) and incremental shuttle walk test (ISWT) are valid and reliable measures to assess exercise capacity of patients with chronic obstructive pulmonary disease (COPD). However, the comparison of correlation between peak oxygen uptake (peak VO2) and 6MWT or ISWT distance has not been investigated. We aimed to investigate the correlation between peak VO2 and 6MWT and ISWT distances in patients with COPD through a meta-analysis.Methods: We systematically searched MEDLINE, Scopus, Embase, and the Cochrane Library up to June 30, 2020 for studies comparing the correlation of peak VO2 with either 6MWT or ISWT in patients with COPD. Meta-analysis was performed with R software using a fixed-effect model. We compared the correlation coefficient and measured the heterogeneity using I2 statistics. Results: We identified 12 studies involving 746 patients. Meta-analysis showed a significant correlation between peak VO2 and 6MWT and ISWT distances (6MWT: r = 0.65, 95% CI: 0.61 to 0.70; ISWT: r = 0.81, 95% CI: 0.74 to 0.85; p < 0.0001). The heterogeneity was lower in ISWT than in 6MWT (6MWT: I2 = 56%, p = 0.02; ISWT: I2 = 0%, p = 0.71). Subgroup analysis showed a higher correlation coefficient in the low exercise capacity group than in the high exercise capacity group in both field tests. No risk of publication bias was identified.Conclusions: 6MWT and ISWT were significantly correlated with peak VO2. The findings suggest that ISWT had a stronger correlation with peak VO2 than did 6MWT in patients with COPD.Trial registration: CRD 42020200139 at crd.york.ac.uk/prospero/