Establishing a DAO Deficiency
While it is possible to measure DAO activity, the tests available can be inaccurate and insufficient. Your doctor can order a lab test for DAO activity, but due to the dynamic nature of metabolic activity and the wide array of variables involved in enzymatic activity at any given point in time, these tests are largely viewed as unreliable.
A blood test can establish both histamine and DAO levels, with a high histamine-to-DAO ratio indicating potential histamine overload. However, it has not been thoroughly established that blood levels of DAO are directly correlated to DAO levels within the GI tract. Further, circulating DAO provides no indication of DAO activity within the gut, where a multitude of factors can block the action of the enzyme.
DAO deficiency is directly correlated with histamine sensitivity and intolerance. Thus, focusing on histamine in the body and in the diet becomes a more effective approach to identifying and addressing DAO deficiency.
Beyond the elimination diet, laboratory testing for DAO activity can also be done through a physician. While these test can be helpful in that they can identify low DAO activity, they cannot provide solutions to your experiences. They can be highly influenced by your diet, medications and other factors, so the results may be inaccurate or insufficient. A blood test can establish both histamine and DAO levels. A high histamine to DAO ratio is a clear sign that histamine may pose a concern. Again, results can be skewed if you have recently consumed high levels of histamine-rich foods or DAO suppressing products, so this test alone cannot be viewed as definitive.