Capillary Fingerprick or Blood Spot Tests for Thyroid Evaluation

Thoughts from Richard Shames, MD

Richard Shames MD

I frequently feature information from Dr. Richard Shames, co-author with his wife Karilee Shames, RN, Ph.D., of several books on thyroid disease, and an integrative physician who has worked with thyroid patients for several decades. Dr. Shames is increasingly relying on specialized capillary fingerprick/blood spot testing for thyroid levels, rather than the traditional thyroid blood tests and analysis done by most laboratories.

This Q & A looks at Dr. Shames' opinions about this form of testing, which is considered somewhat controversial in the conventional medical world. 

Mary Shomon: Why are you increasingly preferring blood spot testing for thyroid tests, rather than standard blood lab tests?

Richard Shames, MD: What I am telling both patients and colleagues is that the reason is simple. While regular testing does a fine job for a great many people, for others (especially the more difficult-to-diagnose cases), these are new and better tests -- which in many cases are even available without a doctor's order -- that evaluate these hormone systems more effectively and more completely in my opinion.

After doing thyroid testing by regular venous blood draw for these last 25 years of hormone practice, I have come to see the superiority of a new technology that appeared in the prior decade. Osteopaths, Nutritionists, Chiropractors, and Naturopathic Doctors were using the new technology and advised us during some of our hormone seminars to give it a try.

What I found, as a medical doctor, was that the blood spot testing from capillary fingerprick gave more definitive results for my most difficult thyroid cases.

For example, when a patient who had regular blood lab tests was still uncomfortable despite normal results, I would do the blood spot finger prick analysis.

(I use the tests from ZRT Laboratory.) This new testing sometimes showed that this supposedly "normal" patient was actually too high or too low in thyroid hormone. When I followed the direction suggested by the new tests in terms of making a change in prescription, the patient frequently finally started to feel better.

Also, when I had a patient who had previously seen many other doctors, including endocrinologists, and had been repeatedly told that they didn't have a thyroid problem because their blood tests were normal, I gave these folks the new testing of finger prick blood spot analysis. Often I saw thyroid antibodies where there had been none previously, or I saw abnormal TSH values on the new testing that regular blood tests had shown as normal -- even using the new range of normal.

This new testing seemed to be so much more helpful to my more difficult patients that I started using these tests for most of my patients, to good advantage. I wanted to understand why this test was superior.

Mary Shomon: Why do you think that you're seeing what you consider to be more accurate results with this new testing, versus traditional tests?

Richard Shames, MD: I spoke with Dr. David Zava, the founder of ZRT Labs, who explained that capillary blood is a more accurate place to measure true levels of available thyroid hormone. Not only is the home-based finger stick test less invasive, less costly, and less of a hassle than having to go to a draw station, but also it has the potential of being more accurate because of where the blood is drawn from.

Moreover, there is an added benefit of taking a few drops of blood and having it dry in seconds on a piece of specially treated filter paper that is then analyzed by very sensitive modern equipment (chemiluminescence method). The dried sample is much more stable than thyroid hormones in a liquid form (a tube of blood serum) as is done in regular labs. This is especially true of the fragile pituitary hormone TSH, considered the gold standard for thyroid evaluation. The molecules of these hormones will degrade more rapidly in a liquid form than in a solid dried state.

People should know that the blood that is drawn in the morning at almost every lab in the US is not run through the machinery for analysis until that evening. During that time, your hormones - especially the important TSH - may end up showing lower on your test result than is accurate for you.

There is the important concern about TSH values: it is not a regular hormone, it is a pituitary hormone that according to the best standards should be refrigerated properly once drawn. Most big labs have satellite centers (draw stations) that courier the blood samples to them. Are these kept at exact proper temperature? Hardly ever. TSH serum is rarely refrigerated.

What this means is that you could be low thyroid with abnormally high TSH but by the end of a long day in a test tube, your levels of TSH that are able to be measured will now be in the normal range. If that's not bad enough, here's something even worse: if you are getting inadequate levels of medicine once you're taking thyroid pills, this inaccuracy could convince your doctor that you are on enough or even too much medicine, and he will likely lower your dose even though you're struggling at the present dose.

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If you are interested in specialized capillary fingerprick/blood spot testing for thyroid levels, there are two ways you can obtain this sort of testing. First, your practitioner can order these new tests for you, in addition to or instead of the traditional tests, via ZRT Laboratories. These tests are also available without a prescription to health consumers in many states, via home test kits. If you want to self-order, you can order directly from ZRT, or save money by getting a free membership in an independent patient consumer advocacy group, such as Canary Club, where you can benefit from the group's volume test discount. More information about ZRT and the Canary Club is available in my article on self-testing for thyroid and hormones.

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