Thyroxine-Binding Protein Electrophoresis, Serum
Method Description Describes how the test is performed and provides a method-specific reference
Radioactive (125)I-T4 is incubated with serum, the mixture is electrophoresed on polyacrylamide gel, and the profile of binding proteins is quantitated by counting the radioactivity in slices of the gel. The binding proteins are separated by both charge and size with prealbumin on the anode side followed by albumin and thyroxine-binding globulin (TBG). Gamma-globulin remains at the origin, and free thyroxine (T4) migrates between albumin and prealbumin. The concentration of (125)I-T4 added will saturate TBG, but not the other T4-binders. The binding is expressed as thyroxine-binding capacity at 100 mcg T4/dL serum. (Roberts RC, Nikolai TF: Assay of thyroxine-binding globulin by polyacrylamide electrophoresis: normal values. Clin Chem 1969;5:367-375; Nikolai TF, Seal US: X-chromosome linked familial decrease in thyroxine-binding globulin activity. J Clin Endocrinol Metab 1966;26:835-841; Davis PJ, Gregerman RI: Separation of thyroxine-binding proteins in human serum at pH 7.4. II. Effect of pH and temperature on the binding capacities of thyroxine-binding globulin [TBG] and thyroxine-binding prealbumin [TBPA]. J Clin Endocrinol Metab 1971;3:699-708)
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.
Wednesday; 8 a.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
Performing Laboratory Location The location of the laboratory that performs the test