Bioequivalence and Bioavailability Forum • Validation of PowerTOST

Validation of PowerTOST [Two-Stage / GS Designs]

posted by Helmut – Vienna, Austria, 2013-10-09 16:10 (4274 d 16:37 ago) – Posting: # 11632
Views: 20,024

Hi Karthik,

❝ In PowerTOST actually what formula they used and how to validate PowerTOST from my end.

❝ According to my SOP I want to mention the formula so if possible pls share to me.

Hint:

library(PowerTOST)

help(PowerTOST)

Scroll down to the general references. For the “exact” method see help(OwensQ). Background and formulas in
{R-folder}/library/PowerTOST/doc/BE_power_sample_size_excerpt.pdf.
For validation of sampleN.TOST() see help(data2x2) and the script test_2x2.R in the /tests-folder. This may serve as an indirect validation of power.TOST() – which is repeatedly called within sampleN.TOST() until the target power is reached.
You can also use the two example data sets of Potvin et al., though you have to use method='shifted' in power.TOST() – since they used the shifted central t-distribution in their simulations for speed reasons.

library(PowerTOST)

n  <- 12

m  <- 'shifted'

a0 <- 0.05

a1 <- 0.0294

Example 1, stage 1
Method B

                                                            power  N_total

Potvin                                                       75.6    14

round(100*power.TOST(alpha=a1, CV=0.1456, n=n, method=m),1)  75.6

sampleN.TOST(alpha=a1, CV=0.1456, method=m)                          14

Method C

                                                            power  N_total

Potvin                                                       84.1    NA

round(100*power.TOST(alpha=a0, CV=0.1456, n=n, method=m),1)  84.1

Example 2, stage 1
Method B

                                                            power  N_total

Potvin                                                       50.5    20

round(100*power.TOST(alpha=a1, CV=0.1821, n=n, method=m),1)  50.5

Method C

                                                            power  N_total

Potvin                                                       64.9    20

round(100*power.TOST(alpha=a0, CV=0.1821, n=n, method=m),1)  65.0

both methods

                                                                   N_total

sampleN.TOST(alpha=a1, CV=0.1821, method=m)                          20

a posteriori power of the pooled data set, both methods

                                                            power

Potvin                                                       66.3

round(100*power.TOST(alpha=a1, CV=0.2167, n=20, method=m),1) 66.7

Again: Don’t use Phoenix/WinNonlin, which reports after stage 1 for Method B (0.0294) power 93.4% (example 1) and 80.4% (example 2)…

If you want to cross-validate PowerTOST() against commercial software (e.g., NQuery Advisor or PASS) use method='shifted' for the latter because it employs the shifted central t-distribution instead of the exact method.

—
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Helmut Schütz

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Complete thread:

Potvin’s 2-stage adaptive design GSD 2012-08-17 20:56 [Two-Stage / GS Designs]
- Potvin’s 2-stage adaptive design + RSABE/ABEL Helmut 2012-08-18 00:39
  - Potvin’s 2-stage adaptive design + RSABE/ABEL GSD 2012-08-31 16:30
    - Tough job Helmut 2012-08-31 18:37
      - Tough job GSD 2012-08-31 19:23
        
        C/D for EMA? Good luck! Helmut 2012-09-01 15:09
      - Surprise? d_labes 2012-09-05 12:57
        
        Got it. Ages for sims to complete Helmut 2012-09-05 13:35
        
        Life belt d_labes 2012-09-05 14:51
        
        Life belt Helmut 2012-09-05 15:20
  - Power for Two stage Design K2K 2013-10-07 14:43
    - Power for Two stage Design Helmut 2013-10-07 14:59
      - Power for Two stage Design K2K 2013-10-08 14:35
        
        “Interim power” Helmut 2013-10-08 14:58
        
        “Interim power” K2K 2013-10-09 12:39
        
        Validation of PowerTOSTHelmut 2013-10-09 14:10
        Phoenix/WinNonlin - power d_labes 2013-10-09 16:11
        
        Phoenix/WinNonlin - power Helmut 2013-10-09 18:19
        
        power K2K 2013-10-10 08:36