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Test Code T4P T4 (Thyroxine), Total

Additional Codes

EPIC:  LAB126

Methodology

Chemiluminescent Immunoassay


Used in the diagnosis of hypothyroidism and hyperthyroidism, assessing thyroid function in patients with normal thyroxine-binding globulin levels, and monitoring patients on hormone replacement therapy.

Performing Laboratory

St. Joseph Hospital

Specimen Requirements

Preferred:  Plasma

Draw blood in a light green-top (PST - lithium heparin gel) tube(s). (Hemolyzed specimen is not acceptable.) Spin down, separate plasma from cells within 2 hours of collection, and send 1 mL of lithium heparin plasma refrigerated.

Note:  Label specimen as “plasma”. 

Acceptable:  Serum

Draw blood in a plain, red-top tube(s) or SST- serum gel tube(s). (Hemolyzed specimen is not acceptable.) Centrifuge, separate serum from cells within 2 hours of collection, and send 1 mL of serum refrigerated.

Note:  Label specimen as “serum”

Reference Values

Adults:  4.5 - 11.7 µg/dL

Adolescents (13-20Y):   6.0 - 11.6 ug/dL

Children (2-12Y):  6.8 - 12.5 ug/dL

Infants (1-23M)   7.4 - 14.3 µg/dL

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding

84436