Preferred Sample Type

Equilibrium Dialysis free T4 (EDFT4)

Suitable Specimen Types

  • Serum
4 mL of blood (abs min 300uL serum, 900ul if PEG/dilution studies required)

Specimen Transport

First Class Post

Sample Processing in Laboratory

No special requirements

Sample Preparation

Centrifuge and separate serum.

Turnaround Time

28 days

Sample Stability


Equilibrium Dialysis free T4 (EDFT4)

General Information

Equilibrium dialysis free T4 is considered analytically accurate and is the method against which others fT4 methods are compared.  Direct dialysis physically separates free thyroxine from protein-bound thyroxine.  The free component is then measured directly and so is free from interference from antibodies.

This test is only required when the routinely measured thyroid results do not fit the expected pattern or clinical picture.

Patient Preparation



Also called EDFT4. Send clinical details and any previous thyroid function test results including assay method.

Reference Range

Provided by Reference Laboratory


  • EQA Scheme?: No
  • EQA Status:

    None Available - sample exchange

The laboratories at Heartlands Hospital, Good Hope Hospital and Solihull Hospital form part of the services provided by University Hospitals Birmingham and 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:

  • Heartlands, Good Hope and Solihull Hospital pathology laboratories are a UKAS accredited medical laboratory No.8217
  • United Kingdom Health Security Agency laboratory is a UKAS accredited medical laboratory No.8213

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:

Protection of personal information - Laboratory Medicine comply with the Trust Data Protection policy and have procedures in place to allow the Directorate and its employees to comply with the Data Protection act  1998 and associated best practice and guidance.

For further information contact Louise Fallon, Quality Manager, 0121 424 1235