Testosterone, Total and Free, Serum
Method Description Describes how the test is performed and provides a method-specific reference
This method utilizes a radioactive tracer together with equilibrium dialysis to analyze and determine the hostâ€™s serum binding capacity for testosterone. During buffered dialysis, any testosterone that is unbound to SHBG or albumin is free to pass through the semipermeable dialysis tubing, while those testosterone molecules bound to the binding proteins will be held inside the tubing. After dialysis, radioactivity is measured from a sample of the dialysate buffer; the resulting counts are compared to known values to yield a result expressed as a percentage of total testosterone. To yield an absolute free testosterone, the calculated percentage is multiplied by the total testosterone concentration as determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS).(Unpublished Mayo method)
Deuterated stable isotope (d3-testosterone) is added to a 0.2-mL serum sample as an internal standard. Protein is precipitated from the mixture by the addition of acetonitrile. The testosterone and internal standard are extracted from the resulting supernatant by an online extraction utilizing high-throughput liquid chromatography (HTLC). This is followed by conventional liquid chromatography and analysis on a tandem mass spectrometer equipped with a heated nebulizer ion source.(Wang C, Catlin DH, Demers LM, et al: Measurement of total testosterone in adult men: comparison of current laboratory methods versus liquid chromatography-tandem mass spectrometry. J Clin Endocrinol Metab 2004;89:534-543; Taieb J, Mathian B, Millot F, et al: Testosterone measured by 10 immunoassays and by isotope-dilution gas chromatography-mass spectrometry in sera from 116 men, women, and children. Clin Chem 2003;49:1381-1395)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday, Sunday; 1 p.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
See Individual Unit Codes
Performing Laboratory Location The location of the laboratory that performs the test