Blood Spot Test Information

Advantages

  • Convenient for both patient and health care practitioner
  • No phlebotomist, special preparation such as centrifugation of the blood, or special packaging and shipment required, therefore less expensive and more convenient than conventional blood draws
  • Simple and convenient collection of blood at home allows for flexibility of testing at the right time of day or month or following hormone therapy
  • Hormones and other analytes stable in dried blood spot at room temperature for weeks, allowing for greater latitude in collection and shipping
  • Infectious agents such as HIV are inactivated by drying the blood thus allowing for safer transport and lab testing of the blood sample
  • Familiarity of hormone test levels: ranges for hormones in blood spots nearly identical to ranges for conventional serum tests

Blood spot and saliva are both now used for the minimally-invasive hormone testing.  Blood spot testing was originally developed in the 1960s out of a need to screen newborns for phenylketonuria (PKU), since a simple heelstick is more practical than a conventional blood draw in young infants.  Later this was broadened to include tests for congenital hypothyroidism, or slow thyroid.  Today neonatal screening for PKU and thyroid deficiencies using blood spot tests is a routine procedure, and assays for a wide range of other potential health issues in blood spot have been successfully developed.  The simplicity of sample collection, stability of samples in storage and transport, and excellent correlation of blood spot assays with serum tests, have made it an ideal method for epidemiological and field research studies for a variety of health conditions in both children and adults.

The ability to measure accurately levels of steroid hormones in blood spots has important implications for reproductive endocrinology, and also allows effective monitoring of hormone replacement therapy.  This is of particular note for sublingual hormone users, for whom saliva testing is not optimal.  Hormones held in the mouth as a troche or sublingual drops concentrate locally within the oral mucosa, which results in a higher local concentration in the saliva.  This can result in “false high” salivary test results for up to 36 hours, depending on many factors responsible for clearing the locally concentrated hormone from the oral mucosa, including the ability to produce saliva, frequency and types of meals and beverages consumed, and tooth brushing.  The blood spot assay circumvents this problem of “false-high” test results seen in saliva of sublingual hormone users because the capillary blood is taken from a site distal to the oral mucosa, the finger.

Blood spot testing has distinct advantages over conventional serum testing for monitoring topical hormone supplementation.  Levels of steroid hormones produced endogenously are remarkably similar in venipuncture serum and finger stick capillary blood spots.  However, when hormones are delivered topically (transdermally, sublingually, or vaginally), capillary blood spot levels can be much higher than serum levels.  Studies investigating tissue uptake of topically delivered hormones have also shown a striking discrepancy; high tissue hormone levels and much lower serum levels.  For example, topically delivered progesterone at a commonly used physiological dose results in high luteal phase levels of progesterone in capillary blood spots (20-40 ng/ml) and research shows that the same physiological dosing raises the tissue levels of progesterone to a very high luteal phase level (> 20 ng/g tissue).  However, under these same conditions, venipuncture serum progesterone levels only increase marginally to sub-luteal levels (1-3 ng/ml).  The same is seen with saliva versus serum levels, with much higher hormone levels seen in saliva.  This has led to the hypothesis that when hormones are delivered through the skin or oral or vaginal mucosa, conventional serum hormone tests grossly underestimate hormone delivery to tissues.  In contrast, hormone levels in saliva or capillary blood spot better represent tissue hormone uptake.  Using only serum test results to monitor topical progesterone supplementation has led to confusion and can result in over-dosing in an attempt to achieve physiological luteal levels of progesterone.

Blood Spot Collection

Collection of the blood spots is a relatively simple and nearly painless procedure that can be done at home.  A simple nick of the finger followed by placing blood drops on a filter card is all that is needed.  The kit contains easy step-by-step instructions, skin cleansing wipes, two lancets, a filter paper on which the blood drops are collected, and a band-aid.  The dry blood spot sample requires no special handling and is returned, together with a requisition form completed by the patient indicating any current hormone therapy and symptoms, to the laboratory for analysis in a pre-paid return package.  Blood spot samples are collected in the morning before eating or drinking.  Topical hormone users should use their hormones daily as usual but avoid applying the hormones with the hands for several days prior to collection.

Clinical Utility

Blood spot testing can help providers:

  • Identify hormonal deficiencies or imbalances associated with aging and disease, thyroid dysfunction, and symptoms of menopause and andropause
  • Link clinical symptoms to specific hormone imbalances identified by the test
  • Restore hormonal balance and patient quality of life using test results as a rational basis for treatment
  • Monitor patient hormone levels for individualized, physiologic dosing of hormone supplementation
  • Track patient progress with comparative history reports provided with follow-up testing

Customer Support

  • Evaluation report includes test results, details of supplements, and current symptoms reported by the patient
  • The report is available via secure internet access in 5 – 7 business days
  • ZRT Laboratory staff physicians are available for inquiries without appointment, 8:00 a.m. to 5:00 p.m. weekdays

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