Gloved hand hold an empty vial with text bubble saying confusing thyroid blood work: assay intereference

When your doctor assesses or treats your thyroid function, they will usually rely on blood work. Sometimes, we see confusing blood test results, which don’t follow the predictable relationships between the various hormones being tested.

Normal Testing

Usually, testing is straightforward, and results align with symptoms. In cases of hypothyroidism, we expect elevated TSH and diminished T3 and T4. With hyperthyroidism, we expect low TSH and elevated T3 and T4.

a schematic showing thyroid metabolism in hypothyroidism, including T3 and T4 and how when they drop, TSH will increase
thyroid physiology involved in hyperthyroidism showing T3 and T4 hormones have increased expression while TSH drops

Sometimes test results can be confusing, and one reason is assay interference.

Assay Interference

This topic may be a bit technical. Assay interference is basically describing an issue with the test that’s measuring something in our blood. For example, when measuring TSH, the test is quite a sophisticated process, involving measuring antibodies and looking for reactions.

That process, as good as it is, can have errors. Substances may interfere with parts of the test that alters the correct value of the result.  In fact, assay interference is a largely known phenomenon [2], [5]. This too can lead to misinterpretation of patient’s results by the lab or the wrong course of treatment given by the doctor [5].

How Does Assay Interference Affect Things Clinically?

This is an aspect which needs to be considered after all other causes of confusing thyroid lab results are considered. There’s not much to do clinically in this case, other than considering re-testing or going with a watch-and-wait approach.

Talk to your naturopath how we may approach these kinds of issue.


Interested in learning more?

Read on in our series of articles on Thyroid Health!

About the Author - Dr. Johann de Chickera

man facing camera

Dr. Johann is a fully licensed Naturopathic Doctor. His approach emphasizes the importance of living a healthy lifestyle and improving one’s health naturally. Dr. Johann obtained a Doctor of Naturopathy at the Canadian College of Naturopathic Medicine (CCNM). Education at CCNM is a vigorous four years, with a curriculum involving biomedical sciences, physical diagnosis, clinical nutrition, traditional Chinese medicine and acupuncture, botanical (herbal) medicine, physical medicine, homeopathy and lifestyle management.

While Dr. Johann has a general practice, he focuses on fertility, hormonal imbalances, gut health, and autoimmune disease.

To book in please call us at (519) 442-2206 or click here.

Leave a Comment