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Testosterone, Free, Equilibrium Ultrafiltration With Total Testosterone, LC/MS-MS
CPT:
84402; 84403
Special Instructions
State patient's age and sex on the test request form.
Expected Turnaround Time
4 - 6 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Related Documents
For more information, please view the literature below.
Frequently Asked Questions: Testosterone by Mass Spectrometry − New Profiles
Specimen Requirements
Specimen
Serum
Volume
2.2 mL
Minimum Volume
1.8 mL (Note: This volume does not allow for repeat testing.)
Container
Red-top tube or gel-barrier tube
Collection
Serum should be transferred from cells within one hour of collection and transferred to a plastic transport tube.
Storage Instructions
Room temperature
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 7 days |
Refrigerated | 7 days |
Frozen | 5.58 years |
Freeze/thaw cycles | Stable x9 |
Causes for Rejection
Hemolyzed sample; icteric sample; gross lipemia; recently administered isotopes; plasma specimen
Test Details
Use
Evaluate hirsutism and masculinization in women; evaluate testicular function in clinical states in which the testosterone-binding proteins may be altered (obesity, cirrhosis, thyroid disorders)
Limitations
This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.
Methodology
Free: equilibrium ultrafiltration; total: liquid chromatography/tandem mass spectrometry (LC/MS-MS)
Reference Interval
See table.1
Free Testosterone | ||
|---|---|---|
Age | Male (ng/dL) | Female (ng/dL) |
Cord blood | 0.50−2.20 | 0.40−1.60 |
1 to 15 d | 0.15−3.10 | 0.05−0.25 |
1 to 2 m | 0.33−0.80 | 0.01−0.13 |
3 to 5 m | 0.07−1.40 | 0.03−0.11 |
6 to 7 m | 0.04−0.48 | 0.02−0.06 |
6 to 9 y | 0.01−0.32 | 0.01−0.09 |
10 to 11 y | 0.06−0.57 | 0.10−0.52 |
12 to 14 y | 0.14−15.60 | 0.10−0.52 |
15 to 17 y | 8.00−15.90 | 0.10−0.52 |
Adults | 5.00−21.00 | 0.10−0.85 |
Percentage of Total Testosterone | ||
Age | Male (%) | Female (%) |
Cord blood | 2.00−4.40 | 2.00−3.90 |
1 to 15 d | 0.90−1.70 | 0.80−1.50 |
1 to 2 m | 0.40−0.80 | 0.40−1.10 |
3 to 5 m | 0.40−1.10 | 0.50−1.00 |
6 to 7 m | 0.40−1.00 | 0.50−0.80 |
6 to 9 y | 0.90−1.70 | 0.90−1.40 |
10 to 11 y | 1.00−1.90 | 1.00−1.90 |
12 to 14 y | 1.30−3.00 | 1.00−1.90 |
15 to 17 y | 1.80−2.70 | 1.00−1.90 |
Adults | 1.50−4.20 | 0.50−2.80 |
Additional Information
The concentration of free testosterone is very low, typically <2% of the total testosterone concentration. In most men and women, >50% of total circulating testosterone is bound to sex hormone-binding globulin (SHBG) and most of the rest is bound to albumin.1 Routinely available assay methods used to measure total testosterone are not sensitive enough to quantitate accurately the free testosterone fraction directly. Free testosterone is estimated in this profile by an indirect method, equilibrium ultrafiltration. Tritiated testosterone is added to the sample and allowed to come to equilibrium with testosterone in the serum at physiological temperature.2,3 The amount of the added radiolabeled testosterone must be low enough to ensure that the addition will not significantly increase the total testosterone concentration. Once equilibrium is achieved, the free testosterone is separated from the bound testosterone by filtration through a membrane by centrifugal ultrafiltration.4 The radioactivity of the protein-free ultrafiltrate is measured and used to calculate the percent free testosterone. The concentration of free testosterone is then calculated by multiplying the percent free testosterone by the total testosterone concentration.
Footnotes
1. Wheeler MJ. The determination of bioavailable testosterone. Ann Clin Biochem. 1995; 32(Pt 4):345-357 (review). 7486793
2. Klee GG, Heser DW. Techniques to measure testosterone in the elderly. Mayo Clin Proc. 2000; 75(Suppl):S19-S25. 10959211
3. Gronowski AM, Landau-Levine M. Reproductive endocrine function. In: Burtis CA, Ashwood ER, eds. Tietz Textbook of Clinical Chemistry. 3rd ed. Philadelphia, Pa: WB Saunders Co; 1999:1601-1641.
4. Vlahos I, MacMahon W, Sgoutas D. An improved ultrafiltration method for determining free testosterone in serum. Clin Chem. 1982; 28(11):2286-2291. 7127776
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 070038 | Testosterone, F Eqlib+T LC/MS | 58952-3 | 070036 | Testosterone, Total, LC/MS | ng/dL | 2986-8 |
| 070038 | Testosterone, F Eqlib+T LC/MS | 58952-3 | 070039 | Testosterone, Free | ng/dL | 2991-8 |
| 070038 | Testosterone, F Eqlib+T LC/MS | 58952-3 | 080770 | % Free Testosterone | % | 15432-8 |
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