Sample size considerations for establishing clinical bioequivalence of allergen formulations.

Bioequivalence of formulations must be established by proving that the differences between the formulations are within a specified interval according to Equation 1, the Interval Hypothesis. Explicit estimates of sample size determined from Equation 8 and listed in Table 1 are qualitatively larger than those that would be determined from Equation 2, the Hypothesis of No Difference. Equation 8 was derived from the TOST procedure; other valid methods should yield comparable results. In any context, this discussion has illustrated that the failure to demonstrate a difference is not sufficient to demonstrate equivalence, and that a properly powered equivalence study of allergen formulations will generally demand many more than four study subjects.