Table 4

Criteria for feasibility

CriteriaFull trial is not feasible as designedProceed to a full trial without modification in the protocol of the feasibility trial
 Modify the protocol prior to a full trial if…ActionMonitor the study procedures closely if…Close monitoring is not required if…
Blinding of assessorAssessor has a >70% correct guess rate on the group allocation.Identify ways to improve assessor blinding based on the responses or feedback provided by the assessors.70%–90% blinding is found.<10% incorrect guess to the group allocation.
Recruitment rate≤1 participant every weekIdentify reasons for low participation rates or declining participation.
Possible strategies could be changing the study site, increasing the number of study sites, increasing advertising efforts and using incentives for participation.
2–3 participants recruited every week.≥4 participants recruited every week.
Attrition rate (in both arms)>30% total drop-outs at 1 week post-treatment.Identify possible reasons for drop-outs and ways to improve follow-up participation.15%–30% total drop-outs at 1 week post-treatment.<15% total drop-outs at 1 week post-treatment. (
Feasibility of outcome assessment>20% missing data on the secondary outcome measures.Reduce the number of outcome measures.
Identify and use brief versions of outcomes.
10%–20% missing data on the secondary outcome measures.<10% missing data on the secondary outcome measures.
Contamination of intervention62 ≥15% contamination between the groups.Identify reasons for contamination and resolve them.<15% contamination between the groups.0% contamination between the groups.
Score on the credibility of treatment scaleControl condition is >0.50 SD credible than pain education group.Develop a new control condition for the EP trial and pilot test to ensure that its credibility rating is <0.50 SD different from pain education group.-The credibility scores of the two conditions are within 0.50 SD units of each other.
Adherence to treatment<50% attend the treatment session after randomisation.Identify reasons for not attending the treatment session in order to increase attendance in the full trial.50%–80% of the participants attend the treatment session.80% or more of the participants attend the treatment sessions.
Difficulty scaleIf ≥50% participants in the experimental group rate pain education as very difficult, very easy, easy or neither easy nor difficult.Make the intervention a little more challenging if more than half of the participants report 1–3 out of 5 in the difficulty scale, by increasing the depth of the education, by adding more pain biology education content. Whereas if more than half participants report the intervention as very difficult, reduce the complexity. Re-evaluate complexity in a second cohort of at least five participants to ensure appropriate level of difficulty.-≥50% participants in the experimental group rate pain education as a ‘difficult’ intervention (4 out of 5 in the difficulty scale). This is the preferred difficulty level because we want pain education intervention to be difficult enough to challenge participants but not too easy or very difficult.