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I am looking for help on estimation of 90% confidence interval for
log transformed data of AUC (0-inf) for a bioequivalence study. This
study involved two-way crossover, two-period, two-sequence design
with a total of 33 subjects completing the study.
In order to estimate the confidence interval, can some one help me
with the formula and a worked out example for the ease of understanding.
I believe least-squares mean estimate for each formulation needs to
be used to form the difference, together with the standard error.
However, in lack of exact formula i am seeking the help of experts
Thanks in advance for the help.
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The following message was posted to: PharmPK
To calculate 90% CI for Log-Transformed data following are the steps
to be followed (Using SAS Software)
1.Initially Least square means separately for Test and Reference are
calculated using appropriate SAS codes
steps 2- exponential conversion of Earlier calculated Least square
means for Test (say my1) and Reference (say my2)
step 3- Pooled standard deviation is calculated and taking square
root gives Standard error as resultant.
Finally Lower and upper CI's are calculated using formula
lower_ci = exp((my2 - my1 )- (absct*se))*100
upper_ci = exp((my2 - my1) + (absct*se))*100
However your idea is absolutely fine regarding "least-squares mean
estimate for each formulation needs to
be used to form the difference, together with the standard error"
I think this will help you.
Nand Kishore Rawat
Department of Clinical Pharmacology and pharmacokinetics
Ranbaxy Research Laboratories
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