Self-efficacy & risk of persistent shoulder pain: results of a Classification & Regression Tree analysis

This study by Chester et al (2019) was recently published in the British Journal of Sports Medicine. The objective of the study was to provide clinicians with a guide to the most influential factors that predict outcome for people undergoing management for non-surgical musculoskeletal shoulder pain. The study included 1030 people attending physiotherapy for non-surgical musculoskeletal shoulder pain in 11 NHS trusts. Information was collected on 71 patient characteristics such as age, lifestyle and medical history. Further information was collected on clinical examination findings before and during the patient’s first physiotherapy appointment and at a 6-month follow-up appointment. At the 6-month follow-up 811 participants provided information on their shoulder pain and function.

Two validated patient-reported outcome measures were collected at the beginning of the study and again after 6 months. The Shoulder Pain and Disability Index (SPADI) and the Quick Disability of the Arm, Shoulder and Hand (QuickDASH). Various baseline variables were used in the classification analysis trees (CART). Out of the possible 34 variables only 3 were predictive of outcome. These were:

  • Baseline pain or disability measured by SPADI and QuickDASH
    Pain self -efficacy measured by PSEQ
    Patient expectations of “change as a result of physiotherapy treatment” measured on a 7-point Likert scale

The researchers found an expected positive association between pain and disability at baseline testing and at the 6 – month follow-up (i.e. those participants with higher scores at baseline tended to have higher scores at follow-up). What was interesting though is that in the SPADI classification trees, higher pain self efficacy influenced this relationship. Participants with high baseline pain or disability, but with a higher pain self-efficacy score had a reduced likelihood of continued high levels of pain and disability at the 6-month follow-up.

For participants with moderate levels of baseline pain and disability measured with the QuickDASH, patient expectation influenced the association. Participants who expected complete recovery or a huge improvement through physiotherapy treatment did much better than participants who only expected slight improvement.

This multicentre study shows that for a given baseline measure of shoulder pain and disability, there are two influential predictors of patient-rated outcome at a 6-month follow-up, namely pain self-efficacy and patient expectation of change as a result of physiotherapy. This study and the regression tree analyses used provide a useful and simple clinical guide that highlights the influence of patient beliefs and expectations of treatment on outcome, irrespective of the baseline score for pain and disability. Physiotherapy works better when your patients believe it will help them! Based on these results, the researchers suggest that pain self-efficacy and patient expectation should be formally assessed and discussed at the first physiotherapy treatment.