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Intra subject CV

Bioequivalence

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#1 Prasad Tata

Prasad Tata

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Posted 02 July 2018 - 04:01 PM

Can someone tell me where and how to find Intra subject CV in the Bioequivalence output? 

 

Thanks,

 

Prasad



#2 Simon Davis

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Posted 02 July 2018 - 04:22 PM

Certainly Prasad, if you have, for example, a simple 2×2 crossover you can simply go to Final Variance Parameters and read it there.

If your study is a more complicated design, you may need to perform some additional manual steps; see this thread here.

https://support.cert...lty-calculation

Simon.

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  • final_variance_parameter.jpg


#3 Prasad Tata

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Posted 02 July 2018 - 06:04 PM

Thanks Simon:

 

But I am seeing a different screen, 

 

Var(seq*subject)

Var (residual) 

 

for each parameter not the inter  and intra subject variance as you stated.

 

Thanks,

 

Prasad



#4 Simon Davis

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Posted 02 July 2018 - 07:49 PM

Prasad, I have to assume you have specified a different model; The above table came from a BE performed as per FDA guidance;

Fixed terms : int+Sequence+Trt+Period
Random/repeated terms : Sequence*Subject

The EMA requests a different model where "Fixed effects, rather than random effects, should be used for all terms."; this leads to intra subject variances not being calculated; nothing to do with the software used - a result of the model specified. there have been more indepth conversations regarding this on other forums e.g.;
http://forum.bebac.a...=DESC#top4660/>

To expand on my answer above, most probably you have a replicated design; for those cases CV is not output.

Since we have 2 variances, there are 2 random effects specified.

The first one is the residual variance (could be used for CVintrasubject calculation)

The second one is the subject based variance (could be used for CVintersubject calculation). That is, the subject is specified as a pure random effect (see EMA Q&A for details).

Basing on that:

CVintra = 100 * sqrt[ exp( Var (residual)) - 1]

CVinter = 100 * sqrt[ exp( Var(seq*subject)) – 1]

Please also review the WNL User Guide

Simon.

Edited by Simon Davis, 03 July 2018 - 04:46 AM.






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