Q. My friend recently had a hormone test using blood from just a finger prick. A few years ago I had a hormone test using saliva. How do these tests compare to a regular blood test, and is one of these tests better than the other?
A. As �nanotechnology� enters into the field of medicine, what is now called �blood spot testing� may emerge as the future of blood testing. Blood spot testing is simply the testing of blood from a finger prick that has been collected on filter paper and dried. The technique has been used since the early Sixties to screen for phenylketonuria in newborns, and commercially since 2002 to measure levels of a variety of other substances, hormones in particular, in blood. Blood collection from a finger prick is certainly less traumatic than by vein puncture and does not require a trained phlebotomist. Also, if the specimen needs to be transported, it is stable for about a month without requiring refrigeration, so the high cost of overnight delivery is avoided.
Blood spot testing yields results that are virtually the same as the results from blood obtained by vein puncture. A major difference between blood spot testing and saliva testing is that 95% or more of the hormones circulating in blood are bound to proteins such as sex hormone binding globulin, cortisol binding globulin, and albumin. Only the small fraction of hormones not bound to protein is active, although both bound and unbound hormones are measured in the blood test. The saliva hormone test measures only the unbound hormones, a much lower actual amount but the amount that is actually functioning in the body at the time of specimen collection.
Saliva hormone testing has been done for decades and has a couple of advantages over blood spot testing. For instance, when it is necessary to measure hormone levels several times during the day, or at an inconvenient time such as midnight, collecting the saliva specimen is easier than the blood spot. The major disadvantage of saliva hormone testing is that it requires a specialized laboratory because the levels of hormones in blood are 10 to 100 times higher than the hormone levels in saliva, plus recent food or drink choices can interfere with test results. In addition, small amounts of blood in saliva, perhaps from periodontal disease, will cause significant changes in the hormone level.
Saliva hormones are almost always falsely elevated when topical hormone creams are being used. Since the hormone is applied to the skin by the hands, handling the saliva collection container transfers some of the hormone to the container. It takes very little hormone from this source to dramatically affect the test results.
The decision on whether to measure saliva or blood hormone levels should be made with your health care provider. Some peptide hormones can be tested only in blood, but most steroid hormones can be tested in either. Whether blood or saliva is chosen, the information will greatly assist him or her in establishing a complete picture of your overall health. Hormonal imbalances are linked to bone loss, cardiovascular disease, fatigue, depression, general aging, and cancer, particularly breast and prostate cancers. Clues on ways to improve quality of life can be found through hormone testing.
This article appears in January 14 • 2005.