Blood Spot Testing Questions

Why would I choose blood spot testing over saliva or blood serum testing?

Blood spot testing provides results that correlate extremely well to serum testing results in terms of accuracy, but without the cost and inconvenience of conventional blood drawing.

There is no more wasted time and resources going to a lab for a painful blood draw as you collect your sample either at home or in your doctor’s office. In preparation for our CardioMetabolic testing and morning cortisol, which both must be done upon waking, blood spot testing is particularly convenient after an all night fast. Blood spot testing is also a preferred method for those supplementing with troches or sublingual hormones. Use of these particular oral supplements can cause false high saliva testing results due to high concentrations of hormone in the oral mucosa for several days following your last dosage. Blood spot testing allows people who use these oral supplements to continue taking their hormones while testing. Blood spot testing is also preferable for those who have dry mouth conditions such as Sjogren’s Syndrome or who otherwise have difficulty collecting enough saliva for testing. In addition, some of ZRT’s tests are only offered in blood spot, such as thyroid, CardioMetabolic, and Vitamin D.

Choose Blood Spot testing if you:

  • Use troche or sublingual (dissolved under the tongue) hormones
  • Cannot create enough saliva
  • Would rather perform a finger stick
  • Want to measure a hormone that is only tested in blood spot

How are finger-stick dried blood spot and venipuncture blood serum different?

First, one is "whole" blood drawn from the end of the finger. This is mostly capillary blood as opposed to blood drawn from the arm, which is venous blood. The former contains nutrients, hormones, and oxygen to feed the tissues. The latter is partially spent of these life-giving components and is returning to the heart, lungs, and gastrointestinal tract to pick up another load.

Second, dried blood spots are comprised of whole blood complete with blood cells, whereas serum is the watery component that remains after lab technicians separate blood cells from venipuncture blood (i.e., blood drawn from veins using a syringe). Therefore, any hormones bound to any removed blood cells during the separation process are lost. Consequently, test results from blood spots reflect a more accurate assessment of your correct capillary blood hormone levels than test results from serum. Since capillary blood is what feeds the cells of your body, hormones detected in capillary blood reflect a more accurate assessment of hormone levels that affect your body’s tissues.

Are hormone results from blood spots different from conventional venipuncture serum?

Yes and no.

The answer is “No” when hormones are produced within the body (endogenously), or are slowly delivered into the body with a transdermal patch (e.g., estradiol patch) or by pellet insertion. In these situations, hormone test results are remarkably similar from finger-stick dried blood spots and serum. In fact, hormone ranges established for blood spots are nearly identical to those of serum.

The answer is “Yes” when steroid hormones are delivered rapidly into the body through the skin or mucous membranes (e.g., topical or sublingual estradiol, progesterone, and testosterone). When hormones enter the body through the skin or mucous membranes, capillary blood and tissue levels far exceed the levels seen in venous blood. So when topicals or sublinguals are used for hormone supplementation, blood spot testing, using capillary blood from the finger, is a more accurate representation of the amount of hormone delivered to tissues.

Are there any special precautions to take when collecting blood spots?

Yes. Use care if you are applying hormones topically with your hands. Topical hormones can concentrate in the fingers when hormones are applied with the hands, resulting in false high results. It may take 12-24 hours for the hormones in the hands to equilibrate with other tissues in the body. Therefore, when using topical hormones, rub them in without using fingers (e.g. wrist to wrist) for at least two days prior to collection. Skip use of anti-aging creams that may contain hormone traces. It is important to continue to use the hormones as usual during this time; just avoid hand exposure. For additional information on collection when using hormones, see the Blood Spot Testing Collection Instructions in your test kit.

Can whole blood from serum venipuncture be used for the dried blood spot test?

Again, this is a yes and no answer. For peptide hormone analysis (e.g., insulin, LH, FSH, etc.), results are the same for finger-stick capillary whole blood, venipuncture whole blood, and serum. If you are looking at endogenously produced steroid hormones (estradiol, progesterone, testosterone, DHEA-S, cortisol), the results are the same. However, if you have used one of these steroid hormones topically or sublingually, blood spot testing, showing capillary blood hormone levels, gives values much higher and more accurate than the venipuncture blood spot sample. This is because blood cells and serum that exit the capillary beds and return to the venous blood are “spent” of the bioavailable fraction of hormone. In this case, capillary blood more accurately represents tissue levels of the topically delivered hormone.

Are the same tests available for blood spot as saliva?

Yes, but ZRT performs more tests in blood spot than in saliva.

In saliva, we test:

  • AM Cortisol (C1)
  • PM Cortisol (C4)
  • Diurnal Cortisol (C1, C2, C3, C4)
  • DHEA-S (DS)
  • Estradiol (E2)
  • Estriol (E3)
  • Estrone (E1)
  • Progesterone (Pg)
  • Testosterone (T)

In blood spot, we test:

  • AM Cortisol (C1)
  • Cholesterol, total
  • HDL Cholesterol
  • LDL Cholesterol
  • VLDL Cholesterol
  • DHEA-S (DS)
  • Estradiol (E2)
  • Fasting Insulin
  • Follicle Stimulating Hormone (FSH)
  • Hemoglobin A1c (HbA1c)
  • High-Sensitivity C-Reactive Protein (hs-CRP)
  • Insulin (fasting)
  • Insulin-like Growth Factor (IGF-1)
  • Luteinizing Hormone (LH)
  • Progesterone (Pg)
  • Prostate Specific Antigen (PSA)
  • Sex Hormone Binding Globulin (SHBG)
  • Testosterone (T), total
  • Thyroid Peroxidase Antibodies (TPO)
  • Thyroid Stimulating Hormone (TSH)
  • Thyroxine (T4) free
  • Triglycerides (TG)
  • Triiodothyronine (Free T3)
  • Vitamin D, 25-OH, Total

Saliva testing measures the free or bioavailable fraction of hormone. Does blood spot testing measure the same thing?

Blood spot testing measures the total amount of hormone available to tissues, but when divided by the amount of Sex Hormone Binding Globulin (SHBG), this ratio then determines how much of the hormone is bioavailable. So, by combining estradiol or testosterone with SHBG testing, it is possible to determine the bioavailable fraction of these hormones indirectly. This is why we included the SHBG test in our Female and Male Hormone Profiles in Blood Spot.