Observation-based assessment of functional ability in patients with chronic widespread pain: a cross-sectional study.

Knowledge about functional ability, including activities of daily living (ADL), in patients with chronic widespread pain (CWP) and fibromyalgia (FMS) is largely based on self-report. The purpose of this study was to assess functional ability by using standardised, observation-based assessment of ADL performance and to examine the relationship between self-reported and observation-based measures of disability. A total of 257 women with CWP, 199 (77%) fulfilling the American College of Rheumatology tender point criteria for FMS, were evaluated with the Assessment of Motor and Process Skills (AMPS), an observation-based assessment providing linear measures of ADL motor and ADL process skill ability (unit: logits). A cutoff for effortless and independent ADL task performance is set at 2.0 for the motor scale and 1.0 for the process scale. A total of 248 (96.5%) had ability measures below the 2.00 ADL motor cutoff and 107 (41.6%) below the 1.00 ADL process cutoff, indicating increased effort and/or inefficiency during task performance as well as a potential need of assistance for community living. Mean ADL motor ability measure was 1.07 and was significantly lower in patients diagnosed with FMS than plain CWP (1.02 vs 1.27 logits, P=.001). Mean ADL process ability measure was 1.09 logits and was without difference between FMS and plain CWP (1.07 vs 1.16 logits, P=.064). Only weak to moderate correlations between self-reported functional ability and observation-based AMPS ability measures were observed. The results of the study support the notion of considerable performance difficulties in women with CWP. The everyday life problems are substantial and place the individual at risk of need of support for community living.