tetano
Editor, Senior Moderator
BMJ Open
. 2026 Sep 25;16(9):e121051.
doi: 10.1136/bmjopen-2026-121051.
Julia Kopp 1 , Tala Ballouz 1 , Dominik Menges 1 , Anja Frei 1 , Julia Braun 1 , Lisa Kuenzi 1 , Milo A Puhan 1 , Jan S Fehr 1 , Thomas Radtke 2
Affiliations Expand
Objective: To describe the distribution and day-to-day variability of EuroQol Visual Analogue Scale (EQ-VAS) values and to estimate a minimal important difference (MID) in adults with post-COVID-19 condition (PCC).
Design: Secondary analysis of pooled EQ-VAS data from both arms of a 12-week randomised, placebo-controlled trial (PYCNOVID) of Pycnogenol (200 mg/day) versus placebo in adults with PCC.
Setting: Single centre study in Switzerland between June 2023 and July 2024.
Participants: Adults with PCC with at least one of the following symptoms: fatigue, post-exertional malaise, dyspnoea or brain fog.
Main outcome measure: EQ-VAS ratings over 7 consecutive days before baseline (randomisation) and at follow-up (after 12 weeks). Weekly mean EQ-VAS values and within-person SDs (wpSD) were calculated. The MID was estimated using distribution-based and anchor-based methods with prespecified correlation criteria, using the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) instrument as the primary anchor, along with additional anchors.
Results: Among 153 participants, baseline EQ-VAS values were low, with a median of 48.7 on a 0-100 scale. Day-to-day variability was considerable, with a median wpSD of 6.4. Distribution-based MID estimates ranged from 5.9 to 8.9 points. FACIT-Fatigue was the only anchor meeting the correlation threshold (ρ≥0.30), yielding an anchor-based MID of 8.96 points. Triangulation of these estimates supported a final MID estimate of 8 EQ-VAS points.
Conclusions: Adults with PCC reported markedly impaired and highly variable health status. Weekly aggregation of daily EQ-VAS ratings likely provides a more robust estimate than single-day assessments. A PCC-specific EQ-VAS MID of 8 points, derived from a chronic, fatigue-predominant PCC population, facilitates interpretation of meaningful change and improves outcome definition and sample size planning in future studies. Applicability to earlier-stage or non-fatigue-predominant PCC populations warrants further investigation.
Trial registration number: NCT05890534.
Keywords: Chronic Disease; EPIDEMIOLOGIC STUDIES; Health; Patient Reported Outcome Measures; Patient-Centered Care; Post-Acute COVID-19 Syndrome.
. 2026 Sep 25;16(9):e121051.
doi: 10.1136/bmjopen-2026-121051.
Within-person variability and the minimal important difference of the EQ-VAS in adults with post-COVID-19 condition: a secondary analysis of data from a single-centre randomised controlled trial
Julia Kopp 1 , Tala Ballouz 1 , Dominik Menges 1 , Anja Frei 1 , Julia Braun 1 , Lisa Kuenzi 1 , Milo A Puhan 1 , Jan S Fehr 1 , Thomas Radtke 2
Affiliations Expand
- PMID: 42790915
- DOI: 10.1136/bmjopen-2026-121051
Abstract
Objective: To describe the distribution and day-to-day variability of EuroQol Visual Analogue Scale (EQ-VAS) values and to estimate a minimal important difference (MID) in adults with post-COVID-19 condition (PCC).
Design: Secondary analysis of pooled EQ-VAS data from both arms of a 12-week randomised, placebo-controlled trial (PYCNOVID) of Pycnogenol (200 mg/day) versus placebo in adults with PCC.
Setting: Single centre study in Switzerland between June 2023 and July 2024.
Participants: Adults with PCC with at least one of the following symptoms: fatigue, post-exertional malaise, dyspnoea or brain fog.
Main outcome measure: EQ-VAS ratings over 7 consecutive days before baseline (randomisation) and at follow-up (after 12 weeks). Weekly mean EQ-VAS values and within-person SDs (wpSD) were calculated. The MID was estimated using distribution-based and anchor-based methods with prespecified correlation criteria, using the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) instrument as the primary anchor, along with additional anchors.
Results: Among 153 participants, baseline EQ-VAS values were low, with a median of 48.7 on a 0-100 scale. Day-to-day variability was considerable, with a median wpSD of 6.4. Distribution-based MID estimates ranged from 5.9 to 8.9 points. FACIT-Fatigue was the only anchor meeting the correlation threshold (ρ≥0.30), yielding an anchor-based MID of 8.96 points. Triangulation of these estimates supported a final MID estimate of 8 EQ-VAS points.
Conclusions: Adults with PCC reported markedly impaired and highly variable health status. Weekly aggregation of daily EQ-VAS ratings likely provides a more robust estimate than single-day assessments. A PCC-specific EQ-VAS MID of 8 points, derived from a chronic, fatigue-predominant PCC population, facilitates interpretation of meaningful change and improves outcome definition and sample size planning in future studies. Applicability to earlier-stage or non-fatigue-predominant PCC populations warrants further investigation.
Trial registration number: NCT05890534.
Keywords: Chronic Disease; EPIDEMIOLOGIC STUDIES; Health; Patient Reported Outcome Measures; Patient-Centered Care; Post-Acute COVID-19 Syndrome.