Biochemistry

Preferred Sample Type

Free T4 (FT4) Thyroxine

Suitable Specimen Types

Serum

Free T4 (FT4) Thyroxine

Specimen Volume

1 mL blood (minimum sample volume 100 uL)

Sample Preparation

Centrifuge

Turnaround Time

1 day

Sample Processing In Laboratory

Usual

Sample Stability

Store at 4 ºC for up to seven days. For longer periods store at -20 ºC.

 

General Information

The thyroid hormone T4 is physiologically part of the regulating circuit of the thyroid gland and has an effect on the general metabolism. The major fraction of the total thyroxine is bound to transport proteins (TBG, prealbumin, and albumin). The free thyroxine (fT4) is the physiologically active thyroxine component. The determination of free thyroxine is an important element in clinical routine diagnostics. Free T4 is measured with TSH when thyroid function disorders are suspected. The determination of fT4 is also suitable for monitoring thyrosuppressive therapy. The determination of free T4 has the advantage of being independent of changes in concentration and binding properties of the binding proteins.

 

Patient Preparation

Patients receiving therapy with biotin (> 5mg/day) should not have samples taken for analysis until at least 8 hours post dose. Patients receiving treatment with lipid lowering agents containing D-T4 should have the treatment suspended 4-6 weeks prior to FT4 measurements to allow the physiological state to become re-established. Fractionated or unfractionated heparin may produce artefactual elevation in measured concentrations of free thyroid hormones.

 

Notes

Any influence that might affect the binding behaviour of the binding proteins can alter the result of the fT4 tests (e.g. drugs, NTIs (Non‑Thyroid‑Illness) or patients suffering from FDH (Familial Dysalbuminemic Hyperthyroxinemia). In rare cases, interference due to extremely high titers of antibodies to analyte or to analyte‑specific antibodies, streptavidin or ruthenium can occur. Please contact the laboratory for further advice if tests results are not consistent with the patient's medical history, clinical presentation and/or other findings, as further interference studies can be performed.

Reference Range

9.0 - 19.0 pmol/L

Source of Reference Range

Abbott Diagnostics

Specifications

  • EQA Status:

    NEQAS

  • EQAS Scheme: Yes

Link to Further Information

https://labtestsonline.org.uk/tests/tsh http://www.british-thyroid-association.org/sandbox/bta2016/uk_guidelines_for_the_use_of_thyroid_function_tests.pdf http://www.thyroidmanager.org/

Tags

free t4 free thyroxine ft4 TFTs thyroid thyroid hormone thyroxine

Creation Date

Monday, 08 August 2011

Modification Date

Tuesday, 05 May 2020

General Information

General information about the website and its content

Read more

Location of Laboratories

Where the laboratories are located and information about the services offered at each laboratory

Read more

Copyright UHB Pathology 2018

Protection of Personal Information – Clinical Laboratory Services comply with the Trust Data Protection Policy and have procedures in place to allow the Directorate and it’s employees to comply with the Data Protection Act 1998 and associated best practice and guidance.

University Hospitals Birmingham medical laboratories at Queen Elizabeth Hospital, Heartlands Hospital, Good Hope Hospital and Solihull Hospital are UKAS (United Kingdom Accreditation Service) accredited to the ISO 15189:2012 standard. For a list of accredited tests and other information please visit the UKAS website using the following link: https://www.ukas.com/find-an-organisation/

  • Molecular Pathology is a UKAS accredited medical laboratory No. 8759
  • Biochemistry is a UKAS accredited medical laboratory No. 8910
  • Haematology and Transfusion is a UKAS accredited medical laboratory No. 8784
  • Clinical Microbiology is a UKAS accredited medical laboratory No. 8760
  • Cellular Pathology is a UKAS accredited medical laboratory No. 10141
  • Musculoskeletal laboratory is a UKAS accredited medical laboratory No. 9897
  • Heartlands, Good Hope and Solihull Hospital pathology laboratories are a UKAS accredited medical laboratory No.8217.

Tests not appearing on the UKAS Schedule of Accreditation currently remain outside of our scope of accreditation. However, these tests have been validated to the same high standard as accredited tests and are performed by the same trained and competent staff.

For further test information, please visit the test database: http://qehbpathology.uk/test-database

For further information contact Louise Fallon, Quality Manager, 0121 371 5962