Factors that affect functional capacity in patients with musculoskeletal pain: a Delphi study among scientists, clinicians, and patients

OBJECTIVE: To reach consensus on the most important biopsychosocial factors that influence functional capacity results in patients with chronic nonspecific musculoskeletal pain, arranged in the framework of the International Classification of Functioning, Disability and Health. DESIGN: Three-round, internet-based Delphi survey. SETTING: Not applicable. PARTICIPANTS: Participants were scientists, clinicians, and patients familiar with functional capacity testing. Scientists were invited through purposive sampling based on the number of relevant publications in peer-reviewed journals. The scientists recruited clinicians and patients through snowball sampling. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Consensus was reached if at least moderate influence (25%) was achieved and an interquartile range of no more than 1 point was reached. RESULTS: Thirty-three scientists, 21 clinicians, and 21 patients from 9 countries participated. Participants reached consensus on 6 factors that can influence the outcome of the lifting test, having a median of severe influence (50%-95%): catastrophic thoughts and fear, patient adherence to "doctor's orders," internal and external motivation, muscle power, chronic pain behavior, and avoidance behavior. Motivation, chronic pain behavior, and sensation of pain were the top 3 factors affecting postural tolerance and repetitive movement functional capacity tests. Furthermore, participants reported 28 factors having a median of moderate influence (25%-49%) that could influence the outcome of lifting, postural tolerance, and repetitive movement tests. CONCLUSIONS: Overall, chronic pain behavior, motivation, and sensation of pain are the main factors that can influence functional capacity results. We recommend that scientists and clinicians, respectively, consider the most important factors when planning future studies and when interpreting functional capacity test results