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HelpTest Code FFTST Testosterone, Free and Weakly Bound, With Total Testosterone, LC/MS-MS
Specimen Required
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/tube: Plastic vial
Specimen Volume: 2 mL
Collection Instructions:
1. Within one hour of collection, centrifuge and aliquot 2 mL serum into a plastic vial.
2. Ship refrigerated.
Secondary ID
75642Method Name
Ammonium sulfate precipitation; liquid chromatography/tandem mass spectrometry (LC/MS-MS)
Reporting Name
Testosterone,F/WklyBd+T LC/MSSpecimen Type
SerumSpecimen Minimum Volume
1.4 mL (does not allow for repeat testing)
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Refrigerated (preferred) | 7 days |
| Ambient | 7 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Reference Values
Males:
|
Age: |
Range (ng/dL): |
|
Premature Infants (26 to 28 weeks) Day 4 |
59.0-125.0 |
|
Premature (31-35 weeks) Day 4 |
37.0-198.0 |
|
Newborns |
75.0-400.0 |
|
Prepubertal (1 to 10 years) |
<2.5-10.0 |
1 to 7 Months
Levels decrease rapidly the first week to 20.0-50.0 ng/dL, then increase to 60.0-400.0 ng/dL (mean=190.0) between 20-60 days. Levels then decline to prepubertal range of <2.5-10.0 by seven months.
Females:
|
Age: |
Range (ng/dL): |
|
Premature Infants (26 to 28 weeks) Day 4 |
5.0-16.0 |
|
Premature (31-35 weeks) Day 4 |
5.0-22.0 |
|
Newborns |
20.0-64.0 |
|
Prepubertal (1 to 9 years) |
<2.5-10.0 |
1 to 7 Months
Levels decrease during the first month to <10.0 ng/dL and remain there until puberty.
Puberty:
|
Tanner Stage (Males) |
Age (Years) |
Range (ng/dL) |
Mean (ng/dL) |
|
1 |
<9.8 |
<2.5-10.0 |
4.9 |
|
2 |
9.8-14.5 |
18.0-150.0 |
42.0 |
|
3 |
10.7-15.4 |
100.0-320.0 |
190.0 |
|
4 |
11.8-16.2 |
200.0-620.0 |
372.0 |
|
5 |
12.8-17.3 |
350.0-970.0 |
546.0 |
|
Tanner Stage (Females) |
Age (Years) |
Range (ng/dL) |
Mean (ng/dL) |
|
1 |
<9.2 |
<2.5-10.0 |
4.9 |
|
2 |
9.2-13.7 |
7.0-28.0 |
18.0 |
|
3 |
10.0-14.4 |
15.0-35.0 |
25.0 |
|
4 |
10.7-15.6 |
13.0-32.0 |
22.0 |
|
5 |
11.8-18.6 |
20.0-38.0 |
28.0 |
Adults:
|
≥18 Years |
Range (ng/dL) |
|
Males |
350.0-1030.0 |
|
Females |
|
|
Premenopausal |
10.0-55.0 |
|
Postmenopausal |
7.0-40.0 |
Testosterone % Free+Weakly Bound:
Female: 3.0-18.0%
Male: 9.0-46.0%
Testosterone, F+W Bound:
Female: 0.0-9.5 ng/dL
Male: 40.0-250.0 ng/dL
Day(s) Performed
Daily
Report Available
6 to 10 daysPerforming Laboratory
LabCorp BurlingtonTest Classification
This test was developed, and its performance characteristics determined by LabCorp. It has not been cleared or approved by the Food and Drug Administration.CPT Code Information
84410
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| FFTST | Testosterone,F/WklyBd+T LC/MS | Not Provided |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| Z6079 | Testosterone, Total, LC/MS | 2986-8 |
| Z6080 | Testost. % Free+Weakly Bound | 6891-6 |
| Z6081 | Testost. F+W Bound | 2990-0 |
Useful For
Free and weakly bound testosterone (FWBT), also referred to as bioavailable testosterone, is thought to reflect an individual's biologically active, circulating testosterone. FWBT includes free testosterone and testosterone that is bound to albumin. FWBT does not include sex hormone-binding globulin-bound testosterone. The SHBG-bound fraction is biologically inactive because of the high binding affinity of SHBG for testosterone. The rapid dissociation of "weakly bound" testosterone from albumin results in the availability of essentially all albumin-bound testosterone for steroid-receptor interaction.(1)
Clinical Information
Free and weakly bound (bioavailable) testosterone measurement involves the selective precipitation of sex hormone binding globulin (SHBG) with ammonium sulfate. Tritiated testosterone is added to serum, which is then allowed to come to equilibrium at physiologic temperature. Testosterone bound to SHBG is then selectively precipitated with 50% ammonium sulfate, leaving free and albumin-bound testosterone in solution. The percentage of tritiated label not bound to SHBG is multiplied by the total testosterone to produce the bioavailable testosterone.
Elevated levels of free and weakly bound testosterone (FWBT) are observed in female hirsutism.(2) The measurement of free and weakly bound testosterone in women, when used in conjunction with the assay of the DHEA-S and SHBG, can be used to establish etiology of hirsutism. In males, decreased serum concentrations are associated with hypogonadism. FWBT levels tend to increase during pregnancy but have been found to remain below the upper limit of the reference interval.(3) Total testosterone levels in women decrease by approximately 30% after menopause.(4) Administration of exogenous estrogens has the physiologic effect of increasing SHBG concentrations and suppressing the production of androgens by the ovary.(4) This results in a net decrease in FWBT. Decreased FWBT levels have been associated with diminished libido and loss of bone density.(4,5) FWBT levels in males fall with age at a rate that exceeds that of total testosterone and parallels the drop in DHEA sulfate.(6) This decrease is thought to be caused by diminished testicular production and not due to hypothalamic/pituitary insufficiency.(7) Decreased FWBT was not, however, found to correlate with diminished potency.(8) Since SHBG has been found to increase with age, the FWBT level may be a more reliable indicator of testosterone production than total testosterone.