Triiodothyronine - Free (T-3)

Label Mnemonic:	FT3
Epic code:	LAB137
Order form:	Laboratory Requisition
Supply order:	Supply Order Form
Billing:	Billing Policies
CPT code:	84481

Specimen(s):

Plasma

Collection Medium:

Plasma Separator Tube 4.5 mL

Alternate Collection Media:

Call laboratory for additional acceptable specimen collection containers.

Minimum:

3 mL whole blood in light green top or TWO Microtainer^® devices

Testing Schedule:

24 hrs/day, 7 days a week, including holidays.

Turn Around Time:

1 hour (upon receipt in laboratory)

Reference Range:

Less than 1 month:  1.4-5.5 pg/mL
Less than 1 year:     2-6.9 pg/mL
1 - 5 years:        2.4-6.7 pg/mL
5 - 18 years:       2.3-5.5 pg/mL
Adults:           2.57-4.43 pg/mL

To convert results to ng/dL, multiply result x.1
To convert results to pmol/L, multiply result x 1.54

Comments:

Assay updated with increased tolerance to biotin on February 7, 2023.

Test Limitations:

The assay is unaffected by icterus (bilirubin is less than 66 
mg/dL), hemolysis (Hb is less than 1000 mg/dL), lipemia (Intralipid is 
less than 2000 mg/dL) and biotin is less than 1200 ng/mL (criterion: 
recovery within plus or minus 10% of initial value).

18 commonly used pharmaceuticals were tested in vitro. No interference 
with the assay was found.

Therapeutic concentrations of acetylsalicylic acid and furosemide lead 
to elevated FT3 values.

Autoantibodies to thyroid hormones can interfere with the assay.

The risk of interference from potential immunological interactions 
between test components and rare sera has been minimized by the 
inclusion of suitable additives. In rare cases, interference due to 
extremely high titers of antibodies to streptavidin and ruthenium can 
occur. FT3 contains additives which minimize these effects.  For 
diagnostic purposes, the FT3 findings should always be assessed in 
conjunction with the patient's medical history, clinical examination 
and other findings.

Methodology:

Electrochemiluminescence Immunoassay

Sample Processing:

Centrifuge at a speed and time necessary to get barrier separation of plasma/serum and cells within 1 hour of collection. Send specimen in original tube. Do Not transfer to another tube.
Each sample must be labeled with at least TWO full patient identifiers (First/Last Name & DOB are sufficient for non-UIHC affiliated clients) to avoid sample rejection/delays.

Sample Storage:

Refrigerate.
All sample storage requirements are intended for delivery to UIHC within 24 hours of collection for testing. If samples won't arrive in this time period, please call the UIHC Core Lab for alternative storage/shipping instructions (319-356-3527).

Transport Instructions:

Place labeled specimen into zip-lock type biohazard bag; seal bag.
Place completed requisition into outside pocket of bag.
Transport in cooler with refrigerated coolant packs.

CPT Code:

84481

See Additional Information:
Biotin Interference with Immunoassays