Table 1 Categories of effectiveness (definitions)

Beneficial

Interventions whose effectiveness has been demonstrated by clear evidence from randomised controlled trials, and expectation of harms that is small compared with the benefits.

Likely to be beneficial

Interventions for which effectiveness is less well established than for those listed under "beneficial".

Trade off between benefits and harms

Interventions for which clinicians and patients should weigh up the beneficial and harmful effects according to individual circumstances and priorities.

Unknown effectiveness

Interventions for which there are currently insufficient data or data of inadequate quality.

Unlikely to be beneficial

Interventions for which lack of effectiveness is less well established than for those listed under "likely to be ineffective or harmful".

Likely to be ineffective or harmful

Interventions whose ineffectiveness or harmfulness has been demonstrated by clear evidence.