study day based on 2 different drugs

[eric2]

Hi,

 I have a scenario where we have SCREENING, VISIT1, VISIT2 and so on. 

VISIT1  gets Drug A , while VISIT2 gets DrugA+DrugB and Drug B is the actual study drug. Certain labs are done at SCREENING, VISIT1, VISIT2. should we consider RFSTDTC date as VISIT2 date. If yes, then all the VISIT1 study days will be negative. If we consider RFSTDTC as VISIT1 date but then IG says RFSTDTC should be "study drug". Any thoughts on what visit date should be mapped to RFSTDTC.

[data_null__]

What is the problem with STDY being negative for VISIT 1?  

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@eric2 wrote:

Hi,

 I have a scenario where we have SCREENING, VISIT1, VISIT2 and so on. 

VISIT1  gets Drug A , while VISIT2 gets DrugA+DrugB and Drug B is the actual study drug. Certain labs are done at SCREENING, VISIT1, VISIT2. should we consider RFSTDTC date as VISIT2 date. If yes, then all the VISIT1 study days will be negative. If we consider RFSTDTC as VISIT1 date but then IG says RFSTDTC should be "study drug". Any thoughts on what visit date should be mapped to RFSTDTC.

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[eric2]

EX domain will be having negative study days, which may thrown P21 error

[mkeintz]

It seems to me that you want to treat the number of days between visit1 and visit2 either as a predictor whose influence you want to assess. After all the protocol apparently requires issuing DRUG A on visit1. Do you want to get an estimate of the impact of time between DRUGA   and DRUGA+DRUGB?

Or is the time between visiti1 and visit2 just a covariate whose influence you want to remove in studying the impact of the study drug (assuming you have folks with just DRUGA issue at visist1 and visit2). 

In either case, it seems to me that the date variable of interest is the time between visit1 and visit2. 

[eric2]

we are not estimating the time impact between VISIT1 and VISIT2. This is more geared to SDTM question than analysis question but at any rate i wanted to check if there is any issue if we use VISIT1 date as RFSTDTC.