Figure 3.

Trial sequential analysis of incidence of shivering under spinal anaesthesia in 21 trials. We calculated an alpha-spending adjusted required information size of 148 patients using α = 0.05 (two-sided), β = 0.20 (power = 80%), diversity (D²) = 47%, an anticipated relative risk reduction of 66.1% and an event proportion of 44.2% in the control arm. The cumulative z-curve (blue) was constructed using a random-effects model. If the cumulative z-curve crosses the trial sequential monitoring boundary, a sufficient level of evidence has been reached and no further trials are needed. If the z-curve does not cross the boundary and the required information size has not been reached there is insufficient evidence to reach a conclusion. The required information size (148 patients) was reached and the z-curve crossed the conventional boundary for benefit. The TSA adjusted confidence interval was 0.25 to 0.41.