ARUP's Laboratory Test Directory

0070140: Thyroxine

Test Mnemonic: T4
Methodology: Electrochemiluminescent Immunoassay

Performed: Sun-Sat

Reported: Within 24 hours

Specimen Required:  
Collect: One 4 mL SST or PST.  Also acceptable:  One 3 mL lavender (EDTA).

Transport: 1 mL serum or plasma at 2-8°C. (Min: 0.5 mL)  Submit specimen in an ARUP Standard Transport Tube.

Pediatric Collection/Transport: 0.2 mL serum or plasma at 2-8°C.

Remarks: Allow serum to clot completely at room temperature.  Separate serum or plasma from cells ASAP.

Unacceptable Conditions: Grossly hemolyzed specimens.

Stability: After separation from cells: Ambient: 24 hours; Refrigerated: 1 week; Frozen: 1 month

Reference Interval:
Cord blood: 6.6-17.5 µg/dL                          5-9 years: 6.4-13.3 µg/dL
1-7 days: 11.0-21.5 µg/dL                            10-14 years: 5.6-11.7 µg/dL
8-30 days: 8.2-16.6 µg/dL                            15-20 years: 4.2-11.8 µg/dL
1 month-4 years: 7.2-15.6 µg/dL                  21 years and older: 5.1-14.1 µg/dL

CPT Code(s):
84436