Plasma

Plasma Separator Tube 4.5 mL

Call laboratory for additional acceptable specimen collection containers.

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

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

1 hour (upon receipt in laboratory)

AGE                      MALES/FEMALES
< 12 months              0.8-2.7 ng/dL
1 - 5 years              0.8-1.8 ng/dL
5 years - 18 years       0.90-1.70 ng/dL
18+ years                0.80-1.80 ng/dL

Please print, complete and submit the Advance Beneficiary Notice (ABN) along with the Laboratory Requisition before shipping the specimen.

Reference range for 5 years to adult changed on 11/26/2013.
Reference range for 18 years and older changed on 2/23/2016.

The assay is unaffected by icterus (bilirubin is less than 41 
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).

No interference was observed from rheumatoid factor (up to 1200 U/mL)
and samples from dialysis patients.

No significant interference was demonstrated by high concentrations 
of 17 commonly used pharmaceuticals tested in vitro. At typical 
therapeutic concentrations, furosemide, carbamazepine, phenytoin, 
and levothyroxine sodium (L-T4, synthetic levothyroxine) caused 
elevated free T4 recovery.

The test cannot be used to determine fT4 in patients receiving 
treatment with lipid-lowering agents containing D-T4. If the thyroid 
function is to be checked in such patients, the therapy should be 
interrupted for 4-6 weeks to allow the physiological state to become 
re-established.*

Samples from neonates have not been tested with the FT4 assay.

Auto-antibodies 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 additives. In rare cases, interference due to extremely 
high titers of antibodies to streptavidin ruthenium can occur.

For diagnostic purposes, the FT4 findings should always be assessed in 
conjunction with the patient's medical history, clinical examination 
and other findings.

*Bantle JP, Hunninghake DB, Frantz ID, Kuba K, Mariash CN, Oppenheimer
 JH.  Comparison of Effectiveness of Thyrotropin-Suppressive Doses of
 D- and L-Thyroxine in Treatment of Hypercholesterolemia. Am J Med
 1984;3:475-481.

Electrochemiluminescence Immunoassay

Assay updated with increased tolerance to biotin on 4-16-2024.

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.

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).

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.