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Testosterone, Free, Mass Spectrometry/Equilibrium Dialysis (Endocrine Sciences)
CPT:
84402; 84403
Special Instructions
This method is recommended for testing women, children, and hypogonadal men.
Expected Turnaround Time
6 - 10 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
Specimen Requirements
Specimen
Serum, frozen
Volume
2 mL
Minimum Volume
1 mL (Note: This volume does not allow for repeat testing.)
Container
Gel-barrier tube or red-top tube
Collection
Serum must be separated from cells within 45 minutes of venipuncture. Send serum in a plastic transport tube. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.
Storage Instructions
Freeze
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 6 days |
Refrigerated | 7 days |
Frozen | 2.6 years |
Freeze/thaw cycles | Stable x9 |
Causes for Rejection
EDTA plasma; citrated plasma; hemolysis >5%
Test Details
Use
Free testosterone is the fraction of total testosterone that is not bound to circulating proteins. The free fraction is available to diffuse into target cells to interact with receptors or enzymes. The concentration of free testosterone is low relative to total testosterone, typically <3% of the total testosterone concentration. Total circulating testosterone is bound to sex hormone-binding globulin (SHBG) or albumin. Measurement of total and free testosterone is key in diagnosis of androgen excess or deficiency. Free testosterone is best measured by equilibrium dialysis, while total testosterone is measured by HPLC with tandem mass spectrometry.1-3 Free testosterone is estimated in this profile using these recommended techniques.
Tritiated testosterone is added to the sample and allowed to dialyze across a membrane. Once equilibrium has been achieved, the solutions on both sides of the membrane are sampled to determine the percent free testosterone. Total testosterone is measured by HPLC with tandem mass spectrometry. Serum free testosterone is then calculated by multiplying the percent free testosterone by the total testosterone concentration with unit correction.
Limitations
This method is recommended for testing women, children, and hypogonadal men.
Methodology
Testosterone: high-pressure liquid chromatography (HPLC)/tandem mass spectrometry; free testosterone: equilibrium dialysis
Reference Interval
See tables.
Age | Male (ng/dL) | Female (ng/dL) |
|---|---|---|
Premature Infants | ||
26 to 28 wk, day 4 | 59−125 | 5−16 |
31 to 35 wk, day 4 | 37−198 | 5−22 |
Full-term Infants | ||
Newborns, 1 to 7 m | 75−400 | 20−64 |
Prepubertal Children | ||
1 to 10 y | <2.5−10 | |
1 to 9 y | <2.5-10 | |
Adults | ||
>18 y | 264−916 | |
Premenopausal | 10−55 | |
Postmenopausal | 7−40 | |
Tanner Stage | Male | Female | ||
|---|---|---|---|---|
Age (y) | Testosterone (ng/dL) | Age (y) | Testosterone (ng/dL) | |
I | <9.8 | <2.5−10 | <9.2 | <2.5−10 |
II | 9.8−14.5 | 18−150 | 9.2−13.7 | 7−28 |
III | 10.7−15.4 | 100−320 | 10.0−14.4 | 15−35 |
IV | 11.8−16.2 | 200−620 | 10.7−15.6 | 13−32 |
V | 12.8−17.3 | 350−970 | 11.8−18.6 | 20−38 |
Age | Male | Female | ||
|---|---|---|---|---|
% Free | pg/mL | % Free | pg/mL | |
Full-term Infants | ||||
1 to 15 d | 0.9−1.7 | 1.5−31 | 0.8−1.5 | 0.5−2.5 |
1 to 2 m | 0.4−0.8 | 3.3−18 | 0.4−1.1 | 0.1−1.3 |
3 to 4 m | 0.4−1.1 | 0.7−14 | 0.5−1.0 | 0.3−1.1 |
5 to 6 m | 0.4−1.0 | 0.4−4.8 | 0.5−0.8 | 0.2−0.6 |
Prepubertal Children | ||||
1 to 10 y | 0.4−0.9 | 0.15−0.6 | Same as males | |
Puberty: Comprehensive values for free testosterone by dialysis for both males and females throughout puberty are currently unavailable. | ||||
Male | Female | |||
% Free | pg/mL | % Free | pg/mL | |
Adults | 1.5−3.2 | 52−280 | 0.8−1.4 | 1.1−6.3 |
Footnotes
1. Rosner W, Auchus RJ, Azziz R, Sluss PM, Raff H. Utility, limitations, and pitfalls in measuring testosterone: An Endocrine Society position statement. J Clin Endocrinol Metab. 2007 Feb; 92(2):405-413. 17090633
2. Fritz KS, McKean AJ, Nelson JC, Wilcox RB. Analog-based free testosterone test results linked to total testosterone concentrations, not free testosterone concentrations. Clin Chem. 2008 Mar; 54(3): 512-516. 18171714
3. Miller KK, Rosner W, Lee H, et al. Measurement of free testosterone in normal women and women with androgen deficiency: Comparison of methods. J Clin Endocrinol Metab. 2004 Feb; 89(2):525-533. 14764757
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 500726 | Testosterone Free MS/Dialysis | 2991-8 | 500160 | Testosterone, Total | ng/dL | 2986-8 |
| 500726 | Testosterone Free MS/Dialysis | 2991-8 | 500727 | % Free Testosterone (Dialysis) | % | 15432-8 |
| 500726 | Testosterone Free MS/Dialysis | 2991-8 | 500728 | Free Testosterone, Serum | pg/mL | 2991-8 |
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