T/R ratio for estimation of sample size in BE study of NTI drugs [Power / Sample Size]

posted by Helmut Homepage – Vienna, Austria, 2017-10-25 01:15 (2667 d 05:02 ago) – Posting: # 17917
Views: 7,768

Salam Mahmoud,

❝ Pease, advise me about what is the best T/R ratio to be used for estimating sample size for a BE study of NTI drugs? knowing that the GL to be followed set the 90% CI acceptance range to (90-111.11) for Cmax if a "2x2x2" design be followed.

❝ I'm confused to use T/R ratio of 0.95 or 0.975?!


Both are fine. Note that the FDA requires tighter batch release spec’s for NTIDs. Hence, in function sampleN.NTIDFDA() of PowerTOST the default is 0.975 – contrary to the usual 0.95.

library(PowerTOST)
sampleN.NTIDFDA(CV=0.0945)

+++++++++++ FDA method for NTID's +++++++++++
           Sample size estimation
---------------------------------------------
Study design:  2x2x4
log-transformed data (multiplicative model)
1e+05 studies for each step simulated.

alpha  = 0.05, target power = 0.8
CVw(T) = 0.0945, CVw(R) = 0.0945
True ratio     = 0.975
ABE limits     = 0.8 ... 1.25
Implied scABEL = 0.9054 ... 1.1044
Regulatory settings: FDA
- Regulatory const. = 1.053605
- 'CVcap'           = 0.2142

Sample size search
 n     power
16   0.777210
18   0.831050

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