A simple method to estimate sample sizes for safety equivalence studies using inverse sampling.
Safety equivalence studies may be required to demonstrate that a new procedure or process is at least as safe as a previous one. They usually involve low or very low outcome rates that are often not precisely determined, making patient-based sample sizing uncertain. Using a reverse sampling approach, a method is derived from standard equations to estimate the number of events that need to be observed to demonstrate equivalence using the confidence interval approach. For instance, for a one-sided (nonsuperiority) hypothesis, 5% alpha risk, and 80% power, almost 100 events need to be observed in each study arm to demonstrate equivalence within 30%, or 250 events for 20% equivalence. The number of patients to be included can be derived directly from expected event rates.
Moore
Nicholas
N
Départment de Pharmacologie, Université Victor-Segalen, Case 36, 33076, Bordeaux, Cedex, France. nicholas.moore@pharmaco.u-bordeaux2.fr <nicholas.moore@pharmaco.u-bordeaux2.fr>
Tubert-Bitter
Pascale
P
Fourrier
Anne
A
Bégaud
Bernard
B
D016001:Confidence Intervals; D015340:Epidemiologic Research Design; D006801:Humans; D012449:Safety; D018401:Sample Size; D013810:Therapeutic Equivalency