Measuring functioning in people with fibromyalgia (fm) based on the international classification of functioning, disability and health (icf)-a psychometric analysis

Pain Practice, 05/03/2012

This study illustrates that it is possible to measure functioning as a unidimensional construct based on selected ICF categories from the components body functions, as well as activities and participation of the Brief ICF–Core–Set for CWP in patients with FM.


  • 256 people with FM completed the Brief ICF–Core–Set.
  • The Rasch model was used for analysis.
  • Once ordering of response options of ICF categories was ensured, the following properties were studied: fit of the ICF categories to the Rasch model, the targeting between ICF categories and a person’s abilities, unidimensionality, and reliability.


  • Six ICF categories were rescored due to disordered thresholds.
  • Five ICF categories were removed due to high model–misfit and differential item functioning (DIF) for gender.
  • Scores from 46 participants were excluded due to extreme scores.
  • The ICF categories included display consistency with an underlying unidimensional construct, are free of DIF for age, disease duration and gender, display excellent overall reliability, and cover a range of functioning difficulties.

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