A priori feasibility endpoints using a RAG criteria
| Parameter | Red (do not proceed to a further study) | Amber (modifications± further study required) | Green (proceed to a larger study) |
| Recruitment rate | <30% | 30%–60% | >60% |
| Refusal rate | >50% | 30%–50% | <30% |
| Attrition rate | >80% | 20%–80% | <20% |
| Intervention adherence | <30% | 30%–60% | >60% |