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Background Information:

1. This was sent to the lab team for discussion and we decided that the INF-y response tests should be modeled in IS.
2. Craig said there are NO other variables to capture the units and dosing concentrations for the test agents that are added to the samples. In fact, this is a gap in the CDISC model that we lack variables (or a domain) to help mapping in vitro drug/non-drug exposure data. The EX/EC and AG domains are used for mapping in vivo drug and non-drug agents exposure data (respectively). These domains have variables for mapping dosing concentrations and units, but we can't use them for in vitro exposure data. Craig said he would pre-coordinate the concentrations and units of the agents added into the ISCNAGT (test condition agent) variable, see the texts in red in the above example.
   • this is a problem because a single CDISC domain variable should be designed for a single meaning and a single purpose. The Test Condition Agent variable is used for the name/identity of the agent. I think we would be breaking rules to also include the concentration and unit of the agent in this variable as well.
3. While brain storming Stefan's use-case, I remembered that in the MS domain, there are MSAGENT (Agent Name), MSCONC (Agent Concentration), MSCONCU (Agent Concentration Units) variables that were developed back in SDTMIG v3.2 to represent the study and control drugs used for microbial resistance testing. Basically, for these MS tests, you dump antibiotics on a plate to see if the bacteria would be resistant or susceptible for the drug by measuring a few outputs, at differing drug concentrations.

Questions/Discussion Needed:

I want to run this by the team to see if we actually have a "duplicated purpose variable" issue here.

1. Is the Test Condition Agent (ISCNDAGT) variable the same as the Agent Name (MSAGENT)?
2. Do we use them for the same purpose? - they both are used to map the name of the thing/entity (e.g. study/control drug, stimulating test materials like TB antigens) you add to a sample to induce a response.
3. If yes, do we need to merge these two variables? Seeing as we are making changes for IG4.0, this might be worth considering, and will need multiple team's approval.
4. Can we also then extend the use of the standard variables --CONC (Agent Concentration), --CONCU (Agent Concentration Units) to the other specimen-based domains for mapping concentration and unit of the in vitro test agent? There are now use-cases needing these variables in IS, MS and CP.
5. Other concerns....

Here is an MS example from IG3.4:

After E. faecalis was identified in the subject sample, drug susceptibility testing was performed at each of the labs using both the sponsor's investigational drug and amoxicillin. Because an identified organism is the subject of the test, the NHOID variable is populated with "ENTEROCOCCUS FAECALIS". Between the 2 labs (MSNAM), a total of 3 susceptibility testing methods were used: epsilometer, disk diffusion, and macro broth dilution (MSMETHOD). Epsilometer and disk diffusion both use agar diffusion methods, in which an agar plate is inoculated with the microorganism of interest and either a strip (epsilometer) or discs (disk diffusion) containing various concentrations of the drug are placed on the agar plate. The epsilometer test method provides both a  minimum inhibitory concentration (MSTESTCD = "MIC"), the  lowest concentration of a drug  that inhibits the growth of a microorganism, and a qualitative interpretation (MSTESTCD = "MICROSUS") such as susceptible, intermediate, or resistant. The disk diffusion test method provides the diameter of the zone of inhibition (MSTESTCD = "DIAZOINH") and a qualitative interpretation such as susceptible, intermediate, or resistant (MSTESTCD = " MICROSUS" ). The quantitative and qualitative results are grouped together using MSGRPID.

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