The International Classification of Functioning, Disability and Health (ICF) Core Sets for rheumatoid arthritis: a way to specify functioning.

Today, patients' functioning is a central issue in medicine. Concepts, classifications, and measurements of functioning and health, such as the International Classification of Functioning, Disability and Health (ICF) are of prime importance in clinical practice, teaching, and research. This report compares the contents of three of the most widely used health status measures in rheumatoid arthritis (RA), namely the Health Assessment Questionnaire disability index (HAQ), the Arthritis Impact Measurement Scales 2 (AIMS2), and the Short Form health survey (SF-36) based on the ICF. In addition, their content is compared to the Comprehensive ICF Core Set for RA. The comparisons illustrate that the different health status measures cover different components, and that they cover the different components with different level of precision. Using the ICF as a reference framework allows a researcher or a recommending instance to see which domains are covered in a specific instrument and, therefore, whether it is necessary to complement the study with other measures. Nevertheless, which specific health status measures to recommend still remains a challenge. If enough care is taken to define "what should be measured", it could form the basis for a solid and stable recommendation, adhered to for many years.