Measurement properties of the 30-second sit-to-stand test in post COVID-19 condition: Results from the PYCNOVID [RCT], 2026, Braun, Radtke et al.

[Chandelier]

Measurement properties of the 30-second sit-to-stand test in post COVID-19 condition: Results from the PYCNOVID randomised controlled trial

Spoiler: Authors

Braun, Julia; Kopp, Julia; Künzi, Lisa; Puhan, Milo A; Fehr, Jan S; Radtke, Thomas

Abstract​

Background​

The 30-second sit-to-stand test (30s-STS) is a frequently used measure of functional capacity in post-COVID-19 condition (PCC), but its measurement properties have not been comprehensively investigated.

Methods​

We used data from the PYCNOVID randomised controlled trial to examine feasibility, safety, test-retest reliability, construct validity (correlations with key symptoms and physical activity), and responsiveness to change of the 30s-STS.
Data were collected at screening, at baseline (approximately 2 weeks after screening), and at follow-up (12 weeks after baseline).
Using screening and baseline data, agreement was evaluated using Bland-Altman analysis (mean bias and limits of agreement), alongside the intraclass correlation coefficient (ICC) and the minimal detectable change (MDC95).
Correlation coefficients were used to assess relationships between the 30s-STS test, physical activity, and key PCC-related symptoms.
The minimal important difference (MID) was estimated with data from baseline and at 12-weeks using anchor- and distribution-based methods.

Results​

Data from 150 adults with PCC (74.7% female) were analysed.
The 30s-STS was safe (no adverse event) and feasible.
Overall, test performance was reduced, 46% of participants had z-score values below the 5th percentile.
The test showed good test-retest reliability (ICC 0.82 [95% CI, 0.76 to 0.86]) with no indication for a systematic learning effect; however, the limits of agreement were wide.
Mean bias between was 0.84 repetitions (95% CI, 0.26 to 1.42). The MDC95 was 4.25 repetitions.
Correlations with physical activity and key PCC-related symptoms were weak. Distribution-based methods yielded MID values between 1.38 and 3.23 repetitions.
Change correlations between 30s-STS repetitions and the anchors were insufficient for anchor-based MID calculation.

Conclusions​

The 30s-STS test is feasible, safe, and demonstrates good test-retest reliability.
Changes exceeding four repetitions surpass measurement error (MDC95), while distribution-based estimates suggest a provisional MID of two repetitions.
Further studies are needed to establish a triangulated MID to better capture patient-relevant change.

Web | DOI | PMC | PDF | PLOS One | Open Access

 

[Utsikt]

We used data from the PYCNOVID randomised controlled trial to examine feasibility, safety, test-retest reliability, construct validity (correlations with key symptoms and physical activity), and responsiveness to change of the 30s-STS.

Correlations with physical activity and key PCC-related symptoms were weak.

So they have found something to measure, but it doesn’t seem to be linked to symptoms or physical activity (i.e. functional capacity), so it doesn’t really tell us much about the patient’s health. This is a fully expected result, and should have most people question the utility of these tests as useful objective outcomes in e.g. rehab trials that directly target sit-stand performance.

 

[Chandelier]

So they have found something to measure, but it doesn’t seem to be linked to symptoms or physical activity (i.e. functional capacity), so it doesn’t really tell us much about the patient’s health. This is a fully expected result, and should have most people question the utility of these tests as useful objective outcomes in e.g. rehab trials that directly target sit-stand performance.

I don’t think the authors are critical towards the use of this test, though.
From the Discussion:

Relationships between the 30s-STS test and frequent PCC-related symptoms were weak, suggesting that symptom severity is not necessarily a limiting factor for a short and specific functional task such as the 30s-STS test.
Several factors may contribute to this decoupling.
First, participants may adopt pacing or anticipatory behaviours, consciously or subconsciously limiting effort to avoid symptom exacerbation, which can mask the expected relationship between symptoms and performance.
Second, although some individuals may fear symptom worsening, it is unclear whether such a brief, 30-second task is sufficient to trigger PEM.
Finally, there may be a temporal mismatch between the symptom measurement windows and the acute performance during the test, such that momentary functional capacity is not fully captured by symptom questionnaires.

The results of previous studies investigating relationships between 30s-STS performance and PCC-related symptoms are heterogeneous [6,16,17].
Our data are consistent with a previous study of 102 individuals with PCC showing no relationships between the 30s-STS test and fatigue, PEM, myalgia and dyspnoea [16].