Sign in →

Test Code FT4P T4 (Thyroxine), Free, Plasma or Serum

Additional Codes

LAB127

Methodology

Used to monitor thyroid function. Generally used as a second-line test after thyroid-stimulating hormone (TSH) to evaluate changes. Useful for obtaining a more accurate assessment of thyroid status in patients with abnormal T4 binding protein levels when combined with TSH, including those who are pregnant or receiving steroid therapy. When a Thyroid Cascade Profile is ordered, a free T4 will be reflexed if the TSH result is abnormal.

Performing Laboratory

St. Mary's Regional Medical Center-Chemistry

 

CPT: 84439

Specimen Requirements

Submit only 1 of the following specimens:

 

Plasma

Container/Tube: Light green-top (lithium heparin) tube

Specimen: 1 mL of lithium heparin plasma

Transport Temperature: Ambient

Collection Instructions:

Note: 1. Indicate plasma.
2. Label specimen appropriately (plasma).

 

Serum

Container/Tube: Plain, red-top tube or serum gel tube

Specimen: 1 mL of serum

Transport Temperature: Ambient

Collection Instructions:

Note: 1. Indicate serum.
2. Label specimen appropriately (serum).

Reference Values

01-23 months: 0.88-1.48 ng/dL

02-12 years: 0.81-1.35 ng/dL

13-20 years: 0.78-1.33 ng/dL

>20 years: 0.76-1.46 ng/dL

Day(s) Test Set Up

Monday through Sunday