Thyroxine (T4) Free Blood Test, Dialysis

The Thyroxine (T4) Free Blood Test, Dialysis, measures the amount of Free T4 in a blood sample to help assess thyroid hormone function and screen for thyroid disorders.

Quest
LabCorp

Sample Report

Test Code: 501902

CPT Code: 84439

Also Known As: Free Thyroxine (T4) by Dialysis/Mass Spectrometry; FT4

Methodology:

Direct Dialysis Mass Spectrometry • High-pressure Liquid Chromatography/Mass Spectrometry (HPLC/MS)

Specimen Type: Blood

Preparation:

No special preparation is required.

Test Results:

7-9 days. May take longer based on weather, holiday, or lab delays.

Details:

This test measures Free T4 levels using the Direct Dialysis and High-Pressure Liquid Chromatography/Mass Spectrometry (LC/MS-MS) methodologies.

Sample Report

Test Code: 35167

CPT Code: 84439

Also Known As: Free Thyroxine (T4) by Dialysis/Mass Spectrometry; FT4

Methodology:

Equilibrium Dialysis • Chromatography/Mass Spectrometry

Specimen Type: Blood

Preparation:

No special preparation is required.

Test Results:

7-10 days. May take longer based on weather, holiday, or lab delays.

Details:

This test measures Free T4 levels using the Equilibrium Dialysis and Chromatography/Mass Spectrometry methodologies.

Description

What is a thyroid?

The thyroid is a gland in the neck, above the collarbone, shaped like a butterfly. The thyroid is one of the endocrine glands, which produce hormones. These thyroid hormones help regulate the rate of many activities in the body, such as how fast calories are burned and how fast the heart beats.

What is the purpose of this test?

Order this Thyroxine (T4) Free Blood Test, Dialysis, to measure the amount of free T4 in a blood sample to help assess thyroid hormone function and screen for thyroid disorders. Thyroxine Free Direct (T4) is the active form of thyroxine and is a more accurate reflection of thyroid hormone function. The free T4 test is thought by many to be a more accurate reflection of thyroid hormone function, and, in most cases, its use has replaced that of the total T4 test. A total T4 or free T4 test is primarily ordered in response to an abnormal TSH result. However, sometimes healthcare providers will order the T4 test and a TSH to evaluate overall thyroid hormone function. These tests are usually ordered for individuals showcasing signs or symptoms of hyperthyroidism or hypothyroidism.

When should I order the Thyroxine (T4) Free Blood Test, Dialysis?

Individuals may order this panel if they suspect thyroid problems. Common signs or symptoms associated with thyroid malfunction or disorders include: