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Laboratory Medicine

Test Directory / Free Androgen Index

Free Androgen Index

Brown clotted serum, gel barrier

TestFree Androgen Index
Common AbbreviationsFAI
ProfileConsists of testosterone and SHBG
Tube typeBrown clotted serum, gel barrier
Clinical IndicationSex hormone binding protein (SHBG) levels are commonly measured as a supplement to total testosterone because variations in the carrier protein may affect the concentration of testosterone in circulation. The “Free Androgen Index” (FAI) is calculated as the ratio of total testosterone to SHBG and has proved a useful indicator of abnormal androgen status in conditions such as polycycstic ovary syndrome and hirsutism. This is particularly useful when the total testosterone concentration is normal but the SHBG is low, resulting in an elevated concentration of non-protein bound testosterone. FAI is only reported in female patients.
Specimen TypeBlood
Sample typeSerum
Minimum Volume0.5mL If requesting more than 10 tests please send an additional brown clotted serum sample.
Special PrecautionsNo special requirements
StabilitySee Testosterone and Sex Hormone Binding Protein
Turnaround TimeInpatient: 48 hours Outpatient/ GP: 48 hours
Reference IntervalFemales only: 20 - 49 years: 0.3 - 5.6% > 50 years: 0.2 - 3.6%
LimitationsSee Testosterone and Sex Hormone Binding Protein
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