Rasch analysis of the 22 knee injury and osteoarthritis outcome score-physical function items in italian patients with knee osteoarthritis

Franco Franchignoni, Fausto Salaffi, Andrea Giordano, Marina Carotti, Alessandro Ciapetti, Marcella Ottonello

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Objectives: To replicate previous Rasch analysis (RA) that yielded the 7-item Physical Function Short Form of the Knee Injury and Osteoarthritis Outcome Score (KOOS-PS7) in order to verify the consistency of the item selection process, and to analyze its main psychometric properties in a sample of Italian patients with osteoarthritis (OA). Design: Methodological research on cross-sectional data from a convenience sample. Setting: University hospital. Participants: Outpatients with symptomatic OA of the knee (N=200; women, 73%; mean age, 69.4y). Interventions: Not applicable. Main Outcome Measure: The KOOS-PF22 (22 items comprising the 2 KOOS domains of activities of daily living and sport/recreation). Its dimensionality was investigated using exploratory factor analysis. RA was performed on KOOS-PF22, KOOS-PS7, and an item set (called KOOS-PS12) obtained by removing from KOOS-PF22 all misfitting items. Results: KOOS-PF22 showed a 2-factor structure, with the first one largely prevailing. Ten of its 22 items did not fit the Rasch model, while item dependency was present in 7 item pairs. Five of 7 KOOS-PS7 items and all KOOS-PS12 items showed acceptable fit to the Rasch model. The person separation reliability was.79 for KOOS-PS7 and.90 for KOOS-PS12; Cronbach alpha was.81 for KOOS-PS7 and.92 for KOOS-PS12. Conclusions: RA was not able to replicate the selection process of the items included in KOOS-PS7. KOOS-PS7 reliability levels indicate that the instrument seems more useful for group decisions than for everyday clinical application in single patients. To achieve a short form of KOOS-PF22 valid for a wide spectrum of individuals with knee OA, further psychometric studies are warranted.

Original languageEnglish
Pages (from-to)480-487
Number of pages8
JournalArchives of Physical Medicine and Rehabilitation
Volume94
Issue number3
DOIs
Publication statusPublished - Mar 2013

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Knee Injuries
Knee Osteoarthritis
Psychometrics
Recreation
Activities of Daily Living
Osteoarthritis
Statistical Factor Analysis
Sports
Research Design
Outpatients
Outcome Assessment (Health Care)

Keywords

  • Osteoarthritis knee
  • Outcome measures
  • Psychometrics
  • Rehabilitation

ASJC Scopus subject areas

  • Rehabilitation
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Rasch analysis of the 22 knee injury and osteoarthritis outcome score-physical function items in italian patients with knee osteoarthritis. / Franchignoni, Franco; Salaffi, Fausto; Giordano, Andrea; Carotti, Marina; Ciapetti, Alessandro; Ottonello, Marcella.

In: Archives of Physical Medicine and Rehabilitation, Vol. 94, No. 3, 03.2013, p. 480-487.

Research output: Contribution to journalArticle

Franchignoni, Franco ; Salaffi, Fausto ; Giordano, Andrea ; Carotti, Marina ; Ciapetti, Alessandro ; Ottonello, Marcella. / Rasch analysis of the 22 knee injury and osteoarthritis outcome score-physical function items in italian patients with knee osteoarthritis. In: Archives of Physical Medicine and Rehabilitation. 2013 ; Vol. 94, No. 3. pp. 480-487.
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AU - Ciapetti, Alessandro

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AB - Objectives: To replicate previous Rasch analysis (RA) that yielded the 7-item Physical Function Short Form of the Knee Injury and Osteoarthritis Outcome Score (KOOS-PS7) in order to verify the consistency of the item selection process, and to analyze its main psychometric properties in a sample of Italian patients with osteoarthritis (OA). Design: Methodological research on cross-sectional data from a convenience sample. Setting: University hospital. Participants: Outpatients with symptomatic OA of the knee (N=200; women, 73%; mean age, 69.4y). Interventions: Not applicable. Main Outcome Measure: The KOOS-PF22 (22 items comprising the 2 KOOS domains of activities of daily living and sport/recreation). Its dimensionality was investigated using exploratory factor analysis. RA was performed on KOOS-PF22, KOOS-PS7, and an item set (called KOOS-PS12) obtained by removing from KOOS-PF22 all misfitting items. Results: KOOS-PF22 showed a 2-factor structure, with the first one largely prevailing. Ten of its 22 items did not fit the Rasch model, while item dependency was present in 7 item pairs. Five of 7 KOOS-PS7 items and all KOOS-PS12 items showed acceptable fit to the Rasch model. The person separation reliability was.79 for KOOS-PS7 and.90 for KOOS-PS12; Cronbach alpha was.81 for KOOS-PS7 and.92 for KOOS-PS12. Conclusions: RA was not able to replicate the selection process of the items included in KOOS-PS7. KOOS-PS7 reliability levels indicate that the instrument seems more useful for group decisions than for everyday clinical application in single patients. To achieve a short form of KOOS-PF22 valid for a wide spectrum of individuals with knee OA, further psychometric studies are warranted.

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