Patient expectations assessed before randomisation and after the first treatment session, and their associations with pain outcome at 3 months in patients with tennis elbow: a secondary analysis of a randomised controlled feasibility trial in Norwegian secondary care.
OBJECTIVE: To evaluate patients' expectations of pain improvement before randomisation (T1) and after the first treatment (T2), and to examine how expectations at these two time points were associated with pain outcome measured at 3 months (T3). DESIGN: Exploratory secondary analyses of a three-arm, randomised controlled feasibility trial in patients with tennis elbow comparing heavy slow resistance training, shock wave therapy and advice (1:1:1). SETTING: Outpatient clinic at Oslo University Hospital. PARTICIPANTS: Adults with lateral epicondylalgia, commonly known as tennis elbow. MAIN OUTCOME MEASURES: Expected pain was rated on a Numeric Rating Scale (NRS, 0-10) at T1 and T2. Present pain (NRS, 0-10) was reported at 3 months (T3). Changes in expectations from T1 to T2 were summarised descriptively. Univariable linear regressions assessed associations between T3 pain and expectations at T1 and T2, treatment group and baseline factors. Explained variance was quantified by R2. Multivariable models including demographics and baseline pain were evaluated via adjusted R2. RESULTS: Fifty-four participants were included. In the shock wave group, nine (47%) came to expect greater improvement from T1 to T2; by contrast, in the advice group, seven (41%) expected less improvement. Expectations at T1 were not associated with T3 pain, whereas expectations at T2 were positively associated with T3 pain (b=0.61, 95% CI 0.33 to 0.89, p<0.01, R2=0.27), suggesting that higher expected pain at T2 was associated with higher reported pain at T3. Adding education and baseline pain increased explained variance modestly (R2 from 0.27 to 0.32). CONCLUSION: In this study, expectations measured after randomisation and one treatment session were associated with pain at 3 months for patients with tennis elbow. Larger, prospectively designed studies should investigate how postrandomisation expectations relate to clinical outcomes in non-blinded musculoskeletal trials. TRIAL REGISTRATION NUMBER: NCT04803825.