Table 3 |
||
| The complexity spectrum | ||
| Characteristic | Simple | Highly complex |
| 1. Number of components within intervention | One for example, single drug | Several for example, rehabilitation package |
| 2. ‘Dose’ or intensity of intervention | Pre-determined/uniform for example, specified dose drug or pre-prepared information leaflet | Dependent on characteristics or participation of individual for example, exercise intervention |
| 3. Clarity re the components of the intervention | Clearly defined components delivered in a specified order for example, diagnostic procedure | Less well-defined components not delivered in a particular order for example, behavioural intervention |
| 4. Degree of confidence in the ‘active ingredient’ | Known ‘active ingredient’ for example, specific medication | Unknown active ingredient even if components are known for example, smoking cessation activity |
| 5. Timing of intervention | Single event for example, one-off procedure | Protracted intervention or multiple time points for example, follow-up care |
| 6. Number of people involved in delivery | One | Several |
| 7. Clarity of responsibility in intervention | Clearly defined | Ill-defined |
| 8. Number of professional groups involved | One | Several |
| 9. Technical or professional skill involved | Minimal skill for example, sending information by post | Highly skilled for example, surgical procedure |
| 10. Human interaction required to deliver the intervention | Little for example, dispensing of a medication | Intervention is dependent on human interaction for example, counselling |
| 11. Setting | Single well-defined setting for example, single therapy room | Cross boundary or multiple settings for example, hospital at home scheme |
| 12. Level of patient involvement or active participation | Low for example, radiotherapy treatment | High for example, self-care intervention or group activity |
| 13. Sphere of impact | Narrow for example, influences individual patients but no impact on or involvement of rest of service | Broad for example, service development intervention with implications for entire service |
| 14. Clarity of main outcome | Clear and obvious outcome for example, cessation of smoking, length of stay following early discharge | Ambiguous outcome(s) for example, improvement in quality of life or patient satisfaction, multiple outcomes that are all important |
Wells et al. Trials 2012 13:95 doi:10.1186/1745-6215-13-95
