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Regression to the mean for physical function and quality of life in clinical trials for symptomatic knee osteoarthritis

Englund, Martin LU orcid and Turkiewicz, Aleksandra LU (2024) In Osteoarthritis and Cartilage
Abstract

Objective: To estimate the size of regression to the mean (RTM) for common patient-reported outcomes in trials for knee osteoarthritis (OA). Design: Longitudinal cohort study; we included participants of the Osteoarthritis Initiative who fulfilled typical inclusion criteria for enrolment in a trial. These included: age 40–79 years, symptomatic knee OA, Kellgren-Lawrence grade 2–3, use of pain medication more than half the days of a month in past 12 months, numerical rating scale pain of 4 to 9. We studied observed changes in WOMAC physical function and KOOS quality of life (QOL). Results: We identified 547 subjects who fulfilled inclusion criteria on at least one annual follow-up between year 1 and year 8. The mean level of physical... (More)

Objective: To estimate the size of regression to the mean (RTM) for common patient-reported outcomes in trials for knee osteoarthritis (OA). Design: Longitudinal cohort study; we included participants of the Osteoarthritis Initiative who fulfilled typical inclusion criteria for enrolment in a trial. These included: age 40–79 years, symptomatic knee OA, Kellgren-Lawrence grade 2–3, use of pain medication more than half the days of a month in past 12 months, numerical rating scale pain of 4 to 9. We studied observed changes in WOMAC physical function and KOOS quality of life (QOL). Results: We identified 547 subjects who fulfilled inclusion criteria on at least one annual follow-up between year 1 and year 8. The mean level of physical function and QOL at each follow-up time point was similar, about 18 and about 51, respectively. However, at the time of theoretical inclusion in a trial, the mean levels in the same subjects were 23 and 43, respectively (both worse scores). The mean improvement in physical function between inclusion and 1 and 2 years later, respectively, was 2.5 (95% confidence interval 1.7 to 3.2) and 3.1 (2.3 to 3.8). The corresponding improvement in QOL was 2.7 (1.7 to 3.7) and 4.2 (3.1 to 5.3). Conclusion: RTM in trials for knee OA is likely to explain improvement in physical function and QOL, not only in knee pain. RTM often misleads investigators to overinterpret effectiveness as RTM neither represents improvement from the intervention nor placebo effect from the intervention and its context.

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author
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organization
publishing date
type
Contribution to journal
publication status
epub
subject
keywords
Clinical Trial, Function, Osteoarthritis, Quality of life, Treatment Efficacy
in
Osteoarthritis and Cartilage
publisher
W.B. Saunders
external identifiers
  • scopus:85211235427
  • pmid:39608563
ISSN
1063-4584
DOI
10.1016/j.joca.2024.11.006
language
English
LU publication?
yes
id
09df056a-571d-4720-ae8b-f4bff0367606
date added to LUP
2025-01-30 12:01:22
date last changed
2025-06-06 08:18:30
@article{09df056a-571d-4720-ae8b-f4bff0367606,
  abstract     = {{<p>Objective: To estimate the size of regression to the mean (RTM) for common patient-reported outcomes in trials for knee osteoarthritis (OA). Design: Longitudinal cohort study; we included participants of the Osteoarthritis Initiative who fulfilled typical inclusion criteria for enrolment in a trial. These included: age 40–79 years, symptomatic knee OA, Kellgren-Lawrence grade 2–3, use of pain medication more than half the days of a month in past 12 months, numerical rating scale pain of 4 to 9. We studied observed changes in WOMAC physical function and KOOS quality of life (QOL). Results: We identified 547 subjects who fulfilled inclusion criteria on at least one annual follow-up between year 1 and year 8. The mean level of physical function and QOL at each follow-up time point was similar, about 18 and about 51, respectively. However, at the time of theoretical inclusion in a trial, the mean levels in the same subjects were 23 and 43, respectively (both worse scores). The mean improvement in physical function between inclusion and 1 and 2 years later, respectively, was 2.5 (95% confidence interval 1.7 to 3.2) and 3.1 (2.3 to 3.8). The corresponding improvement in QOL was 2.7 (1.7 to 3.7) and 4.2 (3.1 to 5.3). Conclusion: RTM in trials for knee OA is likely to explain improvement in physical function and QOL, not only in knee pain. RTM often misleads investigators to overinterpret effectiveness as RTM neither represents improvement from the intervention nor placebo effect from the intervention and its context.</p>}},
  author       = {{Englund, Martin and Turkiewicz, Aleksandra}},
  issn         = {{1063-4584}},
  keywords     = {{Clinical Trial; Function; Osteoarthritis; Quality of life; Treatment Efficacy}},
  language     = {{eng}},
  publisher    = {{W.B. Saunders}},
  series       = {{Osteoarthritis and Cartilage}},
  title        = {{Regression to the mean for physical function and quality of life in clinical trials for symptomatic knee osteoarthritis}},
  url          = {{http://dx.doi.org/10.1016/j.joca.2024.11.006}},
  doi          = {{10.1016/j.joca.2024.11.006}},
  year         = {{2024}},
}