T4 (Thyroxine)

SIM

50277 

CPT

84436 

Synonyms

Thyroxine; Total T4 

Specimen Type

Plasma or serum 

Container

3.5 ml Green - Lithium heparin plasma separator 
4.0 ml Gold-top serum separator 

(If a TSH is requested along with the T4, only a Gold or Red top tube is the acceptable tube type for both a T4 and a TSH.) 

Collection Instructions

None

Volume

2 ml plasma or serum 
Min: 0.5 ml 

Additional Information

none

Patient Preparation

none

Specimen Processing Instructions

Plasma:  Centrifuge at 3380 rpm’s (±100) for a minimum of 10 minutes

Serum:  Allow to clot.  Centrifuge at 3380 rpm’s (±100) for a minimum of 10 minutes

Centrifuge within 2 hours of collection

Transport Requirements

Refrigerated

Specimen Stability

Room temperature:  8 hours   Refrigerated: 1 day 

Rejection Criteria

•  If not centrifuged within 2 hours of collection. 
•  Gross Hemolysis 

Reference Range

4.5 – 12.0 ug/dl

Critical Value

none 

Test Includes

Total T4 

Methodology

Homogenous Enzymatic Immunoassay 

Testing Frequency

Daily, Monday - Sunday 

Reviewed By

Summer Brochu

Reviewed Date

11.20.21

Supplemental