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Test Code T-4 Thyroxine, Total

Synonyms/Keywords

T4 - Thyroxine, Total

Specimen Requirements

Fasting Required Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)		 Pediatric Minimum Volume
(no repeat)
No Plasma/Serum Lithium Heparin Plasma Separator Tube (PST) Lithium Heparin Green Top Tube (GTT), Serum Separator Tube (SST), Red Top Tube (RTT) 1.0 mL 0.5 mL 0.3 mL

Collection/Processing Instructions

GTT/RTT- physically separate plasma or serum from contact with cells as soon as possible or before transport.

Specimen Stability Information

Specimen Type Temperature Time
Serum Ambient 8 hours
Refrigerated 24 hours
Frozen >24 hours

Rejection Criteria

Gross Hemolysis
Marked Icterus

Test Information

Medicare patients must sign a waiver before specimen is collected since Medicare considers this a non-covered test.

Reference Range Information

Performing Location Reference Range
Marshfield
0 to < 4 years: 5.9-13.1 ug/dL
4 to < 14 years: 5.4-10.1 ug/dL
Female 14 to < 19 years: 5.8-11 ug/dL
Male 14 to < 19 years: 5.3-9.2 ug/dL
Adult (> 19 years):  6.1-12.2 ug/dL

Marshfield Labs Performing Department

Marshfield Labs Chemistry

Performing Information

Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Marshfield Monday through Sunday Less than 2 hours  Immunoenzymatic assay/ Beckman Coulter Unicel DXI

CPT Codes

CPT Modifier
(if needed)		 Quantity Description Comments
84436    1    

Outreach CPT Codes

CPT Modifier
(if needed)		 Quantity Description Comments
84436    1    

Ordering Applications

Ordering Application Description
Cerner Thyroxine