Clinical Practice

Four Markers, One Draw: Reading a Multi-Marker Food Panel in Clinic

Why a panel measuring IgE, IgG, IgG4 and complement C3b/d gives clinicians more to work with than a single-marker result, and how to turn those markers into a usable protocol.

Most clinicians have seen a single-marker food test come back with a long list of flagged foods and no clear next step. The patient reads it as a list of things they can never eat again. The clinician reads it as a page of numbers with limited context. Both reactions are reasonable, because one marker can only answer one question, and food-related immune activity rarely presents as one question.

IS382 COMPLETE measures four markers linked to 382 foods from a single at-home serum collection: IgE, IgG, IgG4 and complement C3b/d. What follows is a practical look at what each marker contributes, and how the combination changes the conversation you have with a patient.

Allergy, sensitivity and tolerance are three different clinical questions

These terms get used interchangeably in patient conversations, and the imprecision costs you time later.

An immediate, IgE-mediated allergic response is a different mechanism, on a different timescale, with a different management pathway than a delayed reaction. A patient who has been told to avoid twenty foods because of a delayed-marker result may be managing that list as though every item carries anaphylaxis risk. A patient with a genuine IgE-mediated concern needs that distinguished clearly from the rest of the picture.

Tolerance matters too. The absence of a raised marker is information. So is a food that shows activity on one marker but not others. Sorting foods into meaningfully different categories, rather than one undifferentiated avoid list, is the part of the work that determines whether a patient can actually follow the plan you write.

What IgG and IgG4 add to the picture

IgE covers the immediate response. IgG and IgG4 relate to delayed immune activity, which is where a lot of the unexplained-symptom conversation lives — the patient with intermittent digestive complaints, the patient with fatigue that does not track to anything obvious, the patient whose inflammatory picture improves and then does not.

NIH studies indicate that at least 20% of the American population have food sensitivities. That is a large enough share of any general caseload that it is worth ruling in or out systematically rather than by trial and error across months of appointments.

Measuring IgG and IgG4 separately, rather than as a combined total, gives you more granularity when you are deciding what to prioritise. Two foods with similar total antibody activity may warrant different handling depending on how that activity is distributed. That is a judgement call, and it is yours to make — the panel supplies the markers, not the conclusion.

Complement C3b/d and the amplification question

The fourth marker is the one most single-marker panels omit. Complement activation can amplify a reaction substantially, which means two patients with comparable antibody levels to the same food may not present comparably.

Clinically, this is useful for sequencing. When you are deciding which foods to remove first in an elimination phase — and you almost always have to choose, because removing everything flagged at once is neither practical nor good practice — complement activity gives you an additional input for that decision. It also helps explain to a patient why a food with a modest antibody value is still on the priority list.

Turning markers into a protocol

The panel is the start of a structured process, not a verdict. A workable approach usually looks like this:

• A defined elimination phase covering a prioritised subset of flagged foods, with a fixed end date the patient knows in advance
• Symptom tracking during that phase, so you have something to compare against
• Staged reintroduction, one food at a time, with enough spacing to attribute any response
• A written plan for what happens after reintroduction, including which foods return to the diet permanently

The reintroduction phase is where most of the clinical value sits, and it is the phase most often skipped. A patient who never reintroduces ends up with a permanently narrowed diet and no better understanding of their own physiology.

Where this fits without adding chair time

Collection happens at home. The patient does not occupy a room, and you do not need new equipment, a phlebotomy setup or additional staff training on collection. For a chiropractic practice looking at food-driven inflammation as a contributing factor in recurring presentations, that means adding a diagnostic input without altering how appointments run.

For dietitians building virtual services, at-home collection removes the geographic constraint entirely. The panel arrives, the patient collects, and the interpretation and protocol-building — the parts that require your expertise — happen over video. That supports a genuine diagnostic service line rather than intake-questionnaire nutrition, and it gives you a defensible reason for the patient to stay engaged through a multi-month reintroduction process.

For union members, testing is available at no cost through insurance, which removes the affordability conversation that otherwise stops many patients before the first collection.

The clinician stays in the loop

IS382 COMPLETE is sold to healthcare providers, not direct to consumers, and that is deliberate. A four-marker panel across 382 foods produces a lot of data, and data of that density needs someone with clinical training to weigh it against history, presentation and everything else in the file. The markers inform your judgement. The plan is still yours to write.