Identification of essential elements of functioning in chronic widespread pain based on a statistical approach

This study aimed to study the most relevant International Classification of Functioning, Disability, and Health (ICF) categories for describing functioning and disability in patients with chronic widespread pain (CWP). The specific aims of the study are (1) to identify which ICF categories explain the most variance of the experience of health in CWP and (2) to compare the identified ICF categories to the ICF categories of the Brief ICF Core Set for CWP.

The ICF categories entered in an initial regression model were selected according to their correlation with item 1 of the Medical Outcomes Survey 36-Item Short-Form Health Survey (SF-36). Based on an initial regression model, additional regression models were performed through systematically substituting the ICF categories included in the initial model with ICF categories from the same chapter with which they highly correlated.

Eleven categories were identified. Six of them are included in the Brief ICF Core Set for CWP.

Most of the categories identified in the regression models are similar to the domains identified in Outcome Measures in Rheumatoid Arthritis Clinical Trials workshops and are represented in the Brief ICF Core Set for CWP, either directly or in ICF categories from the same chapters. Based on the 11 identified categories, clinicians and health professionals can obtain an efficient overview regarding the level of functioning of their patients in those essential areas that best differentiate among various levels of functioning.