Bioequivalence and Bioavailability Forum • T/R ratio for estimation of sample size in BE study of NTI drugs

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

posted by Helmut – Vienna, Austria, 2017-10-25 01:15 (3165 d 09:01 ago) – Posting: # 17917
Views: 9,387

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.NTID() of PowerTOST the default is 0.975 – contrary to the usual 0.95.

library(PowerTOST)

sampleN.NTID(CV = 0.0945)



+++++++++++ FDA method for NTIDs ++++++++++++

           Sample size estimation

---------------------------------------------

Study design:  2x2x4 (TRTR|RTRT)

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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Complete thread:

T/R ratio for estimation of sample size in BE study of NTI drugs mahmoud-teaima 2017-10-24 19:18
- T/R ratio for estimation of sample size in BE study of NTI drugsHelmut 2017-10-24 23:15
  - T/R ratio for estimation of sample size in BE study of NTI drugs ElMaestro 2017-10-25 12:34
    - T/R ratio for estimation of sample size in BE study of NTI drugs nobody 2017-10-26 14:03
      - Defaults in PowerTOST d_labes 2017-10-26 14:49