T4, Total

Test Code

LAB126

Quest Code

867

CPT Codes
84436

Preferred Specimen

1 mL serum

Minimum Volume

0.5 mL

Other Acceptable Specimens

Plasma collected in: Sodium heparin (green-top) or lithium heparin (green-top) tube

Instructions

Note: Free T4 Index (T7) will only be calculated and reported if T3 Uptake is ordered as well

Transport Temperature

Room temperature

Specimen Stability

Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days

Methodology
Immunoassay (IA)

Setup Schedule

Set up: Mon-Sat; Report available: 1-2 days

Limitations

Nonthyroidal chronic diseases, nicotinic acid and nutrition may decrease results. Thyrotoxicosis may not always cause abnormal results. Binding protein variations may cause variations in results. Increases may be associated with pregnancy or oral contraceptive use.

Reference Range

T4 (Thyroxine), Total

	Male (mcg/dL)	Female (mcg/dL)
<1 Month	4.5-17.2	4.5-17.2
1-23 Months	5.9-13.9	5.9-13.9
2-12 Years	5.7-11.6	5.7-11.6
13-20 Years	5.1-10.3	5.3-11.7
>20 Years	4.9-10.5	5.1-11.9

Free T4 Index (T7)

1.4-3.8

Clinical Significance

For diagnosis of hypothyroidism and hyperthyroidism.

Performing Laboratory
Quest Diagnostics Nichols Institute
33608 Ortega Highway
San Juan Capistrano, CA 92675-2042

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.