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23069 Triiodothyronine, Free

Triiodothyronine, Free
Test Code: T3-FREE
Synonyms/Keywords
​​​​T-3, Free, T-3 Free, Free T3, FT3​
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 mL​ 0.5 mL​ 0.3 mL​
  • GTT/RTT - physically separate plasma or serum from contact with cells as soon as possible of before transport.  Separate from cells within 30 minutes to minimize uptake of corticosteroids by RBCs
Collection Processing Instructions
Samples collected in a RTT must be removed from the cells within one hour for storage or transport. Samples collected in gel barrier tubes must be removed from the primary tube prior to transporting to Marshfield. Do not send the primary collection tube.​
Specimen Stability Information

Specimen Type Temperature Time

Plasma/Serum​

​Ambient
​8 hours
Refrigerated​
 2 days
Frozen​ >2 days​

  • ​Thaw samples no more than 3 times
Rejection Criteria
Gross Hemolysis
Gross Icterus
Interference
Human Anti-Murine Antibodies (HAMA) may develop leading to test interference in patients receiving murine-based agents for chemotherapy or tumor-imaging studies.​
 
For testing performed at Weston lab: High doses of exogenous biotin (also termed Vitamin B7, Vitamin H or Coenzyme R) may interfere with this assay. It is recommended that patients refrain from consuming any multivitamin or supplement containing biotin for at least 72 hours prior to collection of a blood sample.
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Weston​ ​Monday through Sunday​ ​Less than 2 hours​ ​Homogeneous Sandwich Chemiluminescent Immunoassay (LOCI)Siemens Dimension
Marshfield​ Monday through Sunday​ Less than 2 hours​
 Beckman Coulter DXI​
Test Information
See Clinical Practice Guidelines for more information​
Reference Range Information
Performing Location Reference Range
Weston
 0-10 years 2.1-5.1 pg/mL
11-18 years 2.1-4.5 pg/mL
>18 years 2.1-4.1 pg/mL ​
​Marshfield
0 to <1 year:  2.8 – 4.5 pg/mL
1 to <15 years:  2.6 – 4.0 pg/mL
Female 15 to <19 years:  2.3 – 3.5 pg/mL
Male 15 to <19 years:  2.5 – 3.7 pg/mL
Adult (>19 years):  2.5 – 3.9 pg/mL​ ​ 
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
84481 ​ ​ ​ ​ ​
Synonyms/Keywords
​​​​T-3, Free, T-3 Free, Free T3, FT3​
Ordering Applications
Ordering Application Description
​​Cerner
 Triiodothyronine, Free
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
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 mL​ 0.5 mL​ 0.3 mL​
  • GTT/RTT - physically separate plasma or serum from contact with cells as soon as possible of before transport.  Separate from cells within 30 minutes to minimize uptake of corticosteroids by RBCs
Collection Processing
Samples collected in a RTT must be removed from the cells within one hour for storage or transport. Samples collected in gel barrier tubes must be removed from the primary tube prior to transporting to Marshfield. Do not send the primary collection tube.​
Specimen Stability Information

Specimen Type Temperature Time

Plasma/Serum​

​Ambient
​8 hours
Refrigerated​
 2 days
Frozen​ >2 days​

  • ​Thaw samples no more than 3 times
Rejection Criteria
Gross Hemolysis
Gross Icterus
Interference
Human Anti-Murine Antibodies (HAMA) may develop leading to test interference in patients receiving murine-based agents for chemotherapy or tumor-imaging studies.​
 
For testing performed at Weston lab: High doses of exogenous biotin (also termed Vitamin B7, Vitamin H or Coenzyme R) may interfere with this assay. It is recommended that patients refrain from consuming any multivitamin or supplement containing biotin for at least 72 hours prior to collection of a blood sample.
Reference Range Information
Performing Location Reference Range
Weston
 0-10 years 2.1-5.1 pg/mL
11-18 years 2.1-4.5 pg/mL
>18 years 2.1-4.1 pg/mL ​
​Marshfield
0 to <1 year:  2.8 – 4.5 pg/mL
1 to <15 years:  2.6 – 4.0 pg/mL
Female 15 to <19 years:  2.3 – 3.5 pg/mL
Male 15 to <19 years:  2.5 – 3.7 pg/mL
Adult (>19 years):  2.5 – 3.9 pg/mL​ ​ 
For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Weston​ ​Monday through Sunday​ ​Less than 2 hours​ ​Homogeneous Sandwich Chemiluminescent Immunoassay (LOCI)Siemens Dimension
Marshfield​ Monday through Sunday​ Less than 2 hours​
 Beckman Coulter DXI​
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
84481 ​ ​ ​ ​ ​
For most current information refer to the Marshfield Laboratory online reference manual.