1 M STST is assessed as sufficient for the measurement qualities; reliability, measurement error, construct validity and responsiveness. The quality of evidence is assessed high for the same measurement qualities.

Criterion validity is assessed as inconsistent with moderate quality of evidence, as two out of four studies had correlation values below the limit for good measurement qualities according to COSMIN (r ≥ 0.7)13. However, the correlation r = 0.4–0.75 in the studies is still moderate to strong19,20,21,23. Studies assessing criterion validity, e.g., validity compared to the 6MWT, underline that the 1 M STST is comparable with the 6MWT21,22,23,24. However, it is relevant to point out that the 6MWT and the 1 M STST assess functional exercise capacity in two different relevant functions of daily life, walking and sit-to-stand. Therefore, they can never be fully comparable.

Several studies in the COSMIN assessment did not include people in a weakened state or with musculoskeletal problems19,21,24,35. Therefore, these people must be assessed individually, which GPs also pointed out in the interviews as a limitation of the test.

The possible implementation of a quick functional test in general practice and some ways to comply with challenges on this matter were analyzed. A large variation in general practises was found, which underlines the importance of cooperating with the specific general practice to uncover the specific factors regarding an implementation. To determine factors influencing the implementation process, specific focus areas were explored from the feasibility concept12: practicality, expansion and demand.

The 1 M STST is considered practical as the only remedies required for carrying out the 1 M STST are a chair and a stopwatch (Supplementary Figure 4). The test protocol is accessible and easy to perform, even considering the registered diversity among the staff members performing tests in general practice36 (Table 2). In regards to expansion the study found that general practice has an average time allotted for annual check-ups of 30 min. The lung function test, used by all interviewed GP’s, varies in time, whether acceptable results are obtained quickly, but requires ~10 min to be performed37. The GPs interviewed defined the test battery used for annual check-ups in general practice as a modulated toolbox, adjustable and dependent on the person’s needs, more than a rigidly defined test battery. If so, it is reasonable to believe that the 1 M STST can be implemented. The results of this study show that the 1 M STST should be included in the test battery based on its relevance to people with COPD.

The general practices in Denmark receive a fixed annual fee per person with COPD27,28,29. This means that implementation will not alter the economic frame as it is fixed annually. In other countries, other financial systems might be in place, but the 1 M STST should be implementable based on its relevance to the person and its accessibility and low requirement for time and space.

Several of the interviewed GPs asked for a quick functional test, and the requested evidence has been determined in this study through the COSMIN methodology. In making test results more tangible and usable for the people and the GP, reference values will be appropriate. For example, a study from 2013 by Strassmann et al. with 6.926 healthy adults gave insight into average values for healthy individuals classified in age and gender38. These reference values and the minimal important difference (MID) of three repetitions for the 1 M STST, will be relevant and useful information for the person and the GP when implementing the test in general practice25.

The 1 M STST complies with all inclusion and exclusion criteria from the initial literature search. It was found that the 1 M STST is valid compared to the 6MWT, and the test results correlate with the quality of life and 2-year mortality23,24,35,39.

In general practice, the MRC-scale assesses the need for pulmonary rehabilitation or intensified focus on physical activity2. One of the interviewed GPs used it for categorizing functional exercise capacity. The MRC-scale is self-reported, and in 2014 Callens et al. found that one in four people with cardio-respiratory disorders over-or underestimated their actual functional exercise capacity on recall, especially people diagnosed with COPD40. Therefore, the MRC-scale is problematic when it comes to identifying the need for intervention regarding physical activity, and the 1 M STST can provide a more objective measure of functional exercise capacity for the GP. Neither the MRC-scale nor the 30STST assess functional exercise capacity in people with COPD as the 1 M STST19,20.

The articles found in our present study also conclude that the 1 M STST has high test-retest reliability (ICC 0.99 (95% CI 0.97–1)) and low learning effect (ICC 0.93 (95% CI 0.83–0.97)), which means that it only needs to be tested once to get a reliable result20,22. This underlines the relevance of the 1 M STST when assessing functional exercise capacity in time-limited settings. The 1 M STST responds to changes in functional exercise capacity and has a MID of three repetitions22,25. These results on the 1 M STST are supported in an extensive systematic review from 2019, where the 1 M STST is recommended, especially in settings where time and space are limited36. A recent study from 2022 also found that having a follow-up using the 1 M STST also had a clinically relevant benefit on functional status in people with COPD41.

The method triangulation in this study has strengthened the feasibility concept by exploring the research aims in different ways from different perspectives. The process of this project was evaluated continuously with the four quality criteria in qualitative projects42. The COSMIN methodology findings in this study are comparable to earlier studies, strengthening the external validity14,15.

The in- and exclusion criteria for the literature search were created to find a quick functional test accessible to all varieties of general practice settings. As they were based on a preconception, the 1 M STST was performed on GPs and other staff members of general practice at a symposium on COPD to examine if it was feasible in general practices. Based on this feed-back, it was concluded that the criteria for the literature research were sufficient to identify a possible, feasible test.

This article explored only objective focus areas from the feasibility concept (Practicality, expansion, demand). Another important focus area, “Acceptability”, about how the patient and the one performing the test experience the 1 M STST, has not been investigated in this study12. None of the included studies have mentioned this either. In an implementation of the 1 M STST into General Practice, the subjective experience of the patient is of paramount importance and should be investigated further in future studies. Most of the interviews were done in one region of Denmark. The e-mail interviews were done with GPs from different areas of Denmark. The similarities in the results justify a generalization of our results to general practices. The variety of staff included and the accessibility of the 1 M STST, compared with the similarities in our results, justifies a generalization of the findings to most general practice.

A possible consequence of the firm structure in the 14 e-mail interviews with the GPs might be that the area regarding factors for implementing a quick functional test has not been fully explored. Focus group interviews could have given a more in-depth view of the barriers and needs in an implementation process. Still, it is believed that this study uncovers variation among general practices concerning attitude towards the test and practicalities.

The results are limited to knowledge about annual check-ups in general practice usable for future research and feasibility studies in this area. Although based on the Danish healthcare system, the results of this study may apply to other healthcare systems internationally, especially regarding the validity and practicality of the 1 M STST and the need for a quick functional exercise capacity test in general practice.

In conclusion, according to COSMIN criteria, the 1 M STST is a valid, reliable, and responsive test to assess functional exercise capacity for people with COPD in general practice. Despite great variation in general practice, the 1 M STST is suitable for implementation because it requires a minimum of time and space for implementation, gives valuable information regarding functional exercise capacity and has therapeutic relevance for people with COPD, especially in general practice.

The results from this study indicate a need among GPs for a quick functional test for people with COPD. The GPs requested that the 1 M STST was valid for assessing functional exercise capacity and that the test was experienced as meaningful for people with COPD. In addition, the 1 M STST works well for factors such as time for consultations, other tests, and economy, which are important in the implementation of a quick functional exercise capacity test.