Free Androgen Index (FAI)

Specimen Required

3-5cc Clotted Blood or Serum

Fasting Required

Purpose of the Test

The Free Androgen Index (FAI) test is used to evaluate the amount of free and bioavailable testosterone in the blood, which is important for the diagnosis and monitoring of various conditions related to androgen levels, such as polycystic ovary syndrome (PCOS), hirsutism, and male hypogonadism.

When this test is required

The test may be ordered when someone has symptoms related to abnormal androgen levels, such as excessive hair growth, acne, irregular menstrual periods, infertility, or erectile dysfunction. It may also be ordered to monitor the effectiveness of hormone therapy or to evaluate the causes of infertility or recurrent miscarriages.

What the Test Detects

The FAI is calculated by dividing the total testosterone concentration in the blood by the sex hormone-binding globulin (SHBG) concentration, which is a protein that binds to and regulates the availability of sex hormones in the body. The resulting ratio reflects the percentage of testosterone that is free and bioavailable for use by the body.

Preparation for the Test

No specific test preparation is required, but you should inform your healthcare provider if you are taking any medications that may affect the results.

Sample Requirements

The test requires a blood sample, usually drawn from a vein in the arm.

Additional Notes

The FAI test is just one of several tests used to evaluate androgen levels, and the results should be interpreted in the context of the individual’s clinical and laboratory findings. Additionally, the FAI may not accurately reflect the true amount of free and bioavailable testosterone in the blood, as other factors, such as albumin levels and other hormone levels, can affect SHBG binding and testosterone availability.

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