balakotu
★

India,
2019-06-18 13:03

Posting: # 20333
Views: 860

## Dose term in the ANOVA Model [Regulatives / Guidelines]

Dear All,

As per the FDA guidance of Sapropterin Dihydrochloride Tablets, The total dose should be included in the ANOVA model. Please any one suggest the terms should be consider in the ANOVA model, since it is a cross over study.

Regards
Kotu

ElMaestro
★★★

Belgium?,
2019-06-18 13:14

@ balakotu
Posting: # 20334
Views: 796

## Dose term in the ANOVA Model

Hi balakotu,

» As per the FDA guidance of Sapropterin Dihydrochloride Tablets, The total dose should be included in the ANOVA model. Please any one suggest the terms should be consider in the ANOVA model, since it is a cross over study.

Thanks for highlighting this.
It is a funny, odd wording. I believe they meant to do an ANCOVA with total dose as covariate.
Your (fixed) factors would be subject, sequence, period, treatment. Note that even with the bogus random statement in SAS when using PROC GLM the model is fit with a single random term (the 'error').

I could be wrong, but...
Best regards,
ElMaestro
Helmut
★★★

Vienna, Austria,
2019-06-18 13:39

@ ElMaestro
Posting: # 20335
Views: 780

## OT: BW in ANCOVA

Hi ElMaestro,

» I believe they meant to do an ANCOVA with total dose as covariate.

So do I.

At the 2nd GBHI conference (Rockville 2016) body weight as a covariate was a hot topic. Body weight changes quite often in studies of anti-cancer drugs. The FDA was happy with that. No way for the EMA – as usual.

Cheers,
Helmut Schütz

The quality of responses received is directly proportional to the quality of the question asked. ☼
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ElMaestro
★★★

Belgium?,
2019-06-18 15:51

@ Helmut
Posting: # 20336
Views: 770

## OT: BW in ANCOVA

Hi Hötzi,

» At the 2nd GBHI conference (Rockville 2016) body weight as a covariate was a hot topic. Body weight changes quite often in studies of anti-cancer drugs. The FDA was happy with that. No way for the EMA – as usual.

So odd.

"The statistical analysis should take into account sources of variation that can be reasonably assumed to have an effect on the response variable."

A larger person has larger plasma volume and will, all other factors equal, be expected to have lower AUC and Cmax. Thus, body weight is definitely a source of variation that can be assumed to have some effect. And this is how it is in practice; those metrics correlate significantly with body weight in many trials albeit not always in a p<0.0000001 fashion when doing e.g. Spearman's rank or Pearson (but hey, period for example is usually not significant but has to be included in the model).

The fact that one can do potency correction in the right circumstances is in fact an introduction of a kind of ANCOVA principle. So why they decide to shut the door on body weight is not clear to me, is it clear to anyone? Does this really have to do with concern for sources of variation, or are we in an altogether different territory here?

I could be wrong, but...
Best regards,
ElMaestro
balakotu
★

India,
2019-06-21 07:31

@ ElMaestro
Posting: # 20354
Views: 685

## Dose term in the ANOVA Model

» » As per the FDA guidance of Sapropterin Dihydrochloride Tablets, The total dose should be included in the ANOVA model.
»
» I believe they meant to do an ANCOVA with total dose as covariate.
» Your (fixed) factors would be subject, sequence, period, treatment. Note that even with the bogus random statement in SAS when using PROC GLM the model is fit with a single random term (the 'error').

Dear ElMaestro,

When i keep totaldose is a factor along with normal fixed effects (seq sub(seq) per trt) the model is not execute, Please let us know what are the fixed effects is required in ANOVA model.

SAS code:
model Cmax AUCt AUCi= seq sub(seq) per trt totaldose / ss3; test h= seq e=sub(seq)/htype=3 etype=3;

Regards
Kotu.

ElMaestro
★★★

Belgium?,
2019-06-21 20:54

@ balakotu
Posting: # 20357
Views: 617

## Dose term in the ANOVA Model

Hello balakotu,

» When i keep totaldose is a factor along with normal fixed effects (seq sub(seq) per trt) the model is not execute, Please let us know what are the fixed effects is required in ANOVA model.
»
» SAS code:
» model Cmax AUCt AUCi= seq sub(seq) per trt totaldose / ss3;» test h= seq e=sub(seq)/htype=3 etype=3;

I am not a SAS user, so I googled this one. It is important to tell the program which ones are fixed factors and which ones are covariates.
Am absolutely not sure, but I believe you might need to use class for seq, sub(seq), per and trt to indicate that those are the fixed effects. For trt and seq this may not be an issue if the stats program does not coerce them to integers or other other numerics. I have no idea if SAS does this in the absence of a class statement.

Otherwise it could have no way to know if you did not mean per and sub(seq) as covariates. Bear in mind the levels of those are typically coded with integers like 1, 2, 3...

I could be wrong, but...
Best regards,
ElMaestro
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