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Coding for Oral Immunotherapy

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(Mark Wlodarski) #1

In our design of a Data Dictionary for the Food Allergy Data Commons we are building we have found what seems to be a gap in the coverage of OMOP’s dictionary.

We are having difficulty coding for the procedure of Oral Immunotherapy.

Oral Immunotherapy takes place in cycles. In the first phase, OIT Initiation, a patient is given an initial small dose of a food compound in a clinical setting and monitored to find how much they are able to handle without having an allergic reaction. Then they return home and take that dose every day, referred to as Home Maintenance. At certain points they visit their doctor for an Up-dosing Visit where they find out if the patient can tolerate a larger amount, and then they return to the Home Maintenance phase.

The code we can find for this is the Measurement code – 43528012 – Ingestion Challenge Test. However this only covers the initial OIT Initiation stage and its classification as a Measurement does not seem correct for this procedure.

For the Home Maintenance phase, either the DEVICE_EXPOSURE or DRUG_EXPOSURE tables seem to fit what we want to represent, which is a patient constantly taking the food extract or compound everyday over a period of time. However we have no Drug or Device codes to represent this. Which of these two tables would work best? Are there existing codes to represent non FDA approved drugs without RxNorm codes, such as those made by a compounding pharmacy?

Finally we have no code for the up-dosing visit, the Ingestion Challenge Test covers only the initial visit. Is there any code we are missing that may cover this?


(Melanie Philofsky) #2

Hi @wlodarmt,

This seems like a Procedure. Similar to skin testing for allergies.

And also a Measurement as “how much they are able to handle” is the result.

What’s your use case? What do you want to know?


(Mark Wlodarski) #3

Bumping this topic in order to hopefully get an answer. We are interested in how this kind of procedure, with the home maintenance and follow up visits is coded.
Are additional procedures “Oral Immunotherapy” and “Oral Immunotherapy follow up” required? The “43528012 – Ingestion Challenge Test” item does not seem sufficient.
Further we are unsure as to how to treat the home maintenance procedure, how would we code for a prescription to a food? As mentioned before this seems similar to the dosages done by a compounding pharmacy, how does OMOP handle those?

Thank you.


(Dmytry Dymshyts) #4

If the combination drug doesn’t exists in RxNorm, we put individual ingredients (which have RxNorm codes) in DRUG_EXPOSURE with the dosage number in quantity (dosage units are stored in Drug_strength - typical units a given ingredient is measured in).
If there’s no code for ingredients, we can create RxNorm Extension concepts generated by our own based on different national drug registries

So, basically you need to know the time interval “Oral Immunotherapy” was given (patient eating small amount of allergen food), right? Unfortunately the PROCEDURE table doesn’t have end_date / end_datetime or days_supply field.
So, the DEVICE_Exposure seems to be the right place. Let’s think of how to name this concept:
Do you want the specific type of food to be encoded, or something like “Food allergen, Oral Immunotherapy dosage”?


(Christian Reich) #5

Friends:

Couple of thoughts:

The Oral Immunotherapy is interesting. People get desensitized by slowly getting fed the allergen. In itself this is a Procedure, as you pointed out. We have an active proposal to add procedure_end_date to the PROCEDURE table, making sure we can have Procedures taking more than a day. I would just use that.

The allergen in your case is food. Food is not a drug. We already decided to use the value_as_string in the OBSERVATION table to capture it, since food is impossible to standardize into concepts. You would then write a PROCEDURE record for the OI, and an OBSERVATION record for the allergen at the same day. If you have to you can connect the two with FACT_RELATIONSHIP, but I personally wouldn’t bother.


(Mark Shapiro) #6

A few comments. The initial challenge for allergen immunotherapy is a diagnostic procedure used to assess sensitivty to the allergen. Is this specific to only the oral immunotherapy? Normally, the starting dose is based on sensitivty from skin testing using histamine as a positive control. Then, there is an initial dose, followed by slow escalation.

I would strongly recommend against considering the allergenic extract to be a “food” even though I assume we’re talking about OIT for peanut. Many groups do compound peanut for OIT, but there is an FDA-approved agent. With allergen immunotherapy, the agent is a biologic rather than a food. Technically the agent is an “allergenic extract” of the allergen. If not compounded for oral use (peanut is the only one that I am aware of people using), these are products approved under a BLA, even though the extract itself is a product derived from the parent compound (grass pollen, cat dander, peanut, etc.).

The units for allergen immunotherapy generally differ. There are standard and non-standard extracts measured in SQU if it is a standardized, alum-adsorbed extract, or PNU (protein nitrogen units) for a non-standard extract, which is stored in a glycerine-phenol-saline solution.


(Mark Wlodarski) #7

I am unsure as to code the initial procedure, while “43528012 – Ingestion Challenge Test” is used by the clinician to bill for the procedure I am not sure how to differentiate Oral Immunotherapy and a normal ingestion challenge. Is there a value I can use to modify it, or would it be better to add a new concept for Oral Immunotherapy.


(Dmytry Dymshyts) #8

I think we can add the new concept to the OMOP Extension
@Alexdavv @Christian_Reich what do you think?


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