Certain drugs inhibit the enzymatic activity of DAO; for example, one of the most known is acetylsalicylic acid or naproxen. However, depending on the type of diagnostic test to be performed or rule out a DAO deficiency, the aspects to be considered will be different.

Migraine, intestinal irregularities, rhinitis, atopic skin, fatigue… Do they sound familiar? Approximately 15% of the world population has a deficiency of Diamine Oxidase (DAO) enzyme without knowing it. Unlike an allergy, when there is a DAO deficiency, the symptom appearance is not linked to the consumption of a certain food, but rather they appear due to an accumulation of their histamine levels. In addition, this alteration in the metabolism of histamine can be reflected in many systems of the body: central nervous system, digestive, cardiovascular, dermal, respiratory and locomotor. As it is a clinical picture with such diverse symptoms, its diagnosis can take years to be carried out. However, when we detect two or more symptoms related to this alteration, there is a high probability that it is a possible DAO deficiency.

In this sense, when we make the first visit to AD Dietistas, we can see two different cases and situations: on the one hand, patients who have a DAO deficiency diagnosis or, on the other, who do not have it, but they have observed that the symptoms fit with a DAO deficiency. In order to reach a correct diagnosis, the different parameters that we currently have to confirm or rule out DAO deficiency must be analyzed.

First of all, if there is a family history of symptoms related to DAO deficiency, it will be interesting to carry out the genetic test. In this case, as we discussed in this article, if the test result is positive, it means that there are one or more alterations in the different genetic variants of the AOC1 gene, which codes for the synthesis of the DAO enzyme.

Secondly, if there is no family history, a blood test is performed to determine the activity of the DAO enzyme. Following this line, certain drugs which inhibit DAO activity have been described; for example, acetylsalicylic acid or better known as Aspirin^®. There are many others that you can consult in this article (in Spanish). In this sense, one of the most frequently asked questions is to know how long it is necessary to be without taking the medication until the test is carried out. In this regard, the following aspects should be considered:

• If the origin of the DAO deficiency is primary (genetic) and the associated genetic variants are analyzed, the result of the test will not be affected by the consumption of inhibitory drugs, since DAO activity is not studied.
• If there is no family history of symptoms related to DAO deficiency, a secondary origin will be suspected (inflammatory bowel diseases, alcohol consumption, surgical interventions, menstrual period, taking certain drugs that block the DAO enzyme…). In this case, the test to be carried out will be to determine the activity of DAO in the blood. It will be necessary to take into account if the patient is taking any drug that inhibits the activity of the enzyme. Thus, it is usually recommended to stop taking the medication a week before the test to avoid interfering with the result to the least extent. If this cannot be the case, the time will be limited to what the patient can sustain without taking the medication.

For this reason, it is important to go to a dietician-nutritionist specialized in DAO deficiency, who can advise and guide the patient in a personalized way, knowing their case and context.