Sample size and study duration
VTE, DVT
EVENTS, DVT
Good quality data for the incidence of VTE in low VTE risk surgical patients not receiving thromboprophylaxis is lacking. Data from the recently published GAPS RCT on moderate and high risk patients reported 29 (1.6%)/1858 VTE events at 90 days.The sample size calculation is for a superiority comparison based on symptomatic VTE (DVT or PE) at 90 days at 90% power with a significance level of 5%, assuming 1.0% in the no stocking (control) and 0.5% in the stocking (active) groups.Assuming an intraclass correlation coefficient (ICC) on the VTE at 90 days outcome of 0.001 (consistent with the control outcome rate varying uniformly between 0.5% and 1.5%)