Protocol based versus mobile application based 6-minute walk test. A validation study

ABSTRACT

Background: The 6-minute walk test (6MWT) is often used as primary endpoint to evaluate exercise capacity in patients with heart failure. However, the 6MWT requires specialized infrastructure, personnel and need to be performed on a track according to a protocol developed by the American Thoracic Society. Especially during the first phases of the current COVID-19 pandemic, patients could not attend follow-up visits for research at the hospitals, and in several studies 6MWT measurements were lost. Purpose: The purpose of our research is to compare 6-minute walking distance (6MWD) measurements obtained according to the protocol and those obtained with a smartphone application (App) by participants themselves. Methods: For this study we asked volunteers to participate. Additionally, we included clinically stable cardiac patients from a RCT-study, where the 6MWD was a primary endpoint. Cardiac patients were excluded when they were unable to fill in questionnaires, perform physical tests, participate in Tele-Yoga (physical activity intervention) or had an expected survival less than 6 months. Participants were asked to perform the 6MWT twice (1) According to the protocol;(2) In the home environment outside with help of an App using global environment positioning system (GPS). Additional data was collected on demographics and how they experienced the weather when walking the 6MWT outside with an App. A Bland-Altman analysis was performed, where the mean of the differences between the 6MD were calculated with the accompanying upper and lower 95% limits of agreement (95%-LOA;mean of the differences ±1.96×standard deviation of the mean of the differences). The intraclass correlation coefficient (ICC) for agreement between protocol based 6WD and 6MWD obtained with the App was calculated. Results: In total, 37 participants were included, with a mean age of 57 years old (21-85), 68% were female (n = 25) and 24% suffered from a cardiac disease (n = 9). The mean 6MWD obtained with the protocol was 613m±102 (cardiac patients 504m±91) and the mean 6MWD obtained with an App was 617m±115 (cardiac patients 493m±61). The mean of the differences between the two tests was-4m±45m (95%-LOA 84m to-99m) (Fig). Only one participant was outside the 95% LOA. This could be explained by cold weather (5-6 Celsius). The overall agreement between both 6MWD was 97% with an ICC of 0.96 (95% CI 0.91-0.98, p < 0.001). Conclusion: When it is not possible to perform the 6MWT according to the protocol, it is possible to use an App that participants can use to assess the 6MWD. Our study shows that the 6MWD measured by an App is feasible and safe. It is important to consider and document weather conditions and advice participants to avoid performing the 6MWT outside with an App when the weather conditions might influence the results, for example when the temperature is very high or very low, or when it is raining or snowing outside.