Background In fibromyalgia, there is a disagreement between patients' self-reports and performances; i.e., subjective and objective status, respectively.
Objectives First, to test the discordance between subjective and objective measures of physical function. Second, to determine whether catastrophizing and self-efficacy are independently associated with this discordance.
Methods Four hundred and five fibromyalgia females and 193 age-matched female controls. Participants filled out the Pain Catastrophizing Scale, Chronic Pain Self-efficacy Scale, and physical functioning subscales of the Revised Fibromyalgia Impact Questionnaire (FIQR) and Short Form-36 (SF-36) health survey. Objective physical function was measured with a battery of performance-based tests (e.g., 6-min walk test). Subjective and objective physical function were expressed as deviation from the general population in standard deviation (SD) units using means and SD of the control group.
Results Fibromyalgia participants reported a worse physical function than performed (p<.001). We found a consistent association of higher catastrophizing with greater discordance between subjective and objective physical function. A significant association of higher self-efficacy with lower discordance was only found when subjective physical function was reported on the SF-36 but not on the FIQR.
Conclusions Although both are markedly impaired, subjective physical function is more impaired than objective physical function in fibromyalgia. Catastrophizing is associated with this discordance. In rehabilitation settings, physical function of fibromyalgia females should be evaluated by both subjective and objective assessments to fully understand their physical function.
Acknowledgements This work was supported by the Spanish Ministry of Economy and Competitiveness [I+D+i DEP2010–15639, I+D+i DEP2013–40908-R, and BES-2014–067612].
Disclosure of Interest None declared