Table 5

Comparison of influences on usual care control group between individually randomised trials and cluster randomised trials.

Possible influence on usual care control group
Individually randomised trials (n = 38)Cluster randomised trials (n = 35)
YesNoNot describedYesNoNot describedP-valuea
 Informed about allocation of patients15815192140.140
 Informed about content of intervention1622223300.002
 Questionnaires before or during trial335052800.280
 Extra information or training111413321110.049
 Risk of learning effect by treating intervention patients151851340<0.001
 Informed consent given352124920.036
 Informed about content of intervention3431012230.018
 Provided with extra information8237017180.001
 Informed about allocation2221421716<0.001
 Questionnaires or examinations3440201500.002
 Risk of contact with intervention patients222403230.200
  • a Statistically tested with 2 test with 2 degrees of freedom.