Laboratory Test Information Guide

Details for Free Androgen Index, Plasma/Serum

Test Name: Free Androgen Index, Plasma/Serum
Alternate Name(s): FAI
Free Testosterone
Laboratory: Core
Specimen Type: Adult:
4.5 mL Light Green top (Li-Heparin) Vacutainer tube

0-2 years: 0.5 mL Light Green top (Li-Heparin) Microtainer
2-10 years: 3 mL Light Green top (Li-Heparin) Vacutainer tube

Red or Gold top tubes are also acceptable

Lavender top (EDTA) tubes are NOT acceptable
Collection Information: Minimum volume of plasma or serum required is 700 L for adult samples or 200 L for pediatric samples.
Test Schedule: Monday - Friday
Turnaround time from when specimen
is received in testing laboratory:
5 days
Reference Range: Male:
20 49 years: 35.0 92.6 %
≥ 50 years: 24.3 72.1 %

20 49 years: 0.3 5.6 %
≥ 50 years: 0.2 3.6 %
Effective Date: 2018-03-06
Revised Date: 2018-08-17
Critical Value:  
Interpretive Comments: The free androgen index (FAI) or free testosterone index (FTI) provides a convenient estimate of the free testosterone level from the independent measurement of both the total testosterone and the sex hormone binding globulin (SHBG) level. It is calculated from the equation:

FAI = total testosterone (nmol/L)/SHBG (nmol/L) expressed as a percentage.

The FAI can be used as a surrogate measure of bio-available testosterone for those cases where the serum albumin level is normal. Results should be interpreted with caution in patients with decreased albumin levels such as nephrotic syndrome or liver cirrhosis.
Special Processing:  
Comments: Biotin may interfere with this test. Samples should not be taken from patients receiving high biotin doses (i.e. > 5 mg/day) until at least 8 hours after the last biotin administration.
Method of Analysis: Roche Electrochemiluminescence
Critical Information Required:  
Storage & Shipment: Store and ship plasma or serum frozen.
System Codes: 
Referred To:  

Questions? Comments? Contact Laura Gopaul