Accuracy of the Six-Minute Walk Test and Duke Activity Status Index in Determining Improvement of Functional Capacity Among Adult Patients Enrolled in Cardiac Rehabilitation

BACKGROUND: The six-minute walk test (6MWT) is a common outcome measurement in cardiac rehabilitation but there are no established guidelines on its use in cardiac rehabilitation. Furthermore, the Duke Activity Status Index (DASI) is a brief self-administered questionnaire that assesses the patient’s ability to perform common activities but its usefulness in cardiac rehabilitation has not yet been determined. This study aimed to assess the reliability of the 6MWT and DASI in determining improvement in functional capacity based on treadmill exercise test (TET) among patients enrolled in Phase I, II and III cardiac rehabilitation in Cardinal Santos Medical Center (CSMC) from September 2015-September 2016. METHODS: This was a prospective analytical study of all patients enrolled in cardiac rehabilitation in CSMC from September 2015 to September 2016. All included patients completed the DASI questionnaire before cardiac rehabilitation and after completion of every Phase. The 6MWT and TET were done after Phase I, II and III of cardiac rehabilitation. The results were correlated with functional capacity using correlation analyses. RESULTS: Among the 85 patients initially included in this study, there were 81, 34 and five patients who finished Phase I, II and III of cardiac rehabilitation, respectively. Progressive improvement of METs was observed with the progression of cardiac rehabilitation. Pearson correlation analysis revealed that peak VO2 based on DASI was moderately correlated with TET at Phase I and II (r=0.623 and 0.594, respectively) while the correlation was not statistically significant at Phase III. The peak VO2 based on 6MWT was also moderately correlated with TET but weaker correlation compared with DASI (r=0.481 and 0.471 for Phase I and Phase II, respectively). The correlation was not statistically significant at Phase III. The Lin concordance correlation coefficients for DASI were moderate for Phase I and II (ρ=0.5985 and 0.5087, respectively) and poor in Phase III (ρ=0.1051). On the other hand, 6MWT had fair agreement with TET in Phase I and Phase II (ρ=0.2432 and 0.3348, respectively). The correlation was not statistically significant at Phase III. Proportional bias was noted with the use of the 6MWT but not with DASI. Conclusion: Stronger correlation was seen with DASI questionnaire than 6MWT in determining functional capacity among patients enrolled in Phase I and II cardiac rehabilitation compared to TET.