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HelpTest Code LAB137 T3 (Triiodothyronine), Free, Plasma or Serum
Additional Codes
45662
Reporting Title
Free T3
Methodology
Roche Diagnostics, Electrochemiluminescence Immunoassay
T3, free is active T3 hormone. Useful in differential diagnosis of Grave’s disease, toxic adenomas, toxic goiter, and excessive T4 therapy.
Performing Laboratory
OhioHealth Laboratory Services-RMH Core Laboratory
Specimen Requirements
Due to interference, patients receiving high doses of biotin (>5 mg/day) should wait at least 8 hours after dose before having blood drawn.
Submit only 1 of the following specimens:
Preferred:
Serum
Draw blood in a gold-top serum gel tube(s). Spin down and
send 1 mL of serum refrigerated.
Note:
1. A speckled-top serum gel tube (s) or a plain, red-top tube(s) is also acceptable.
2. Indicate serum on request form.
3. Label specimen appropriately (serum).
Alternate:
Plasma
Draw blood in a mint green-top (heparin) gel tube(s). Spin down and send 1 mL of heparinized plasma refrigerated.
Note: 1. Indicate plasma on request form.
2. Label specimen appropriately (plasma).
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum or plasma | Refrigerated | 7 days |
| Ambient | 5 days | |
| Frozen | 1 month |
Specimen Transport Temperature
Refrigerate/Frozen OK/Ambient OK
Reference Values
0-60 days: 2.0-5.2 pg/mL
61 days-24 months: 1.5-6.4 pg/mL
25 months-12 years: 2.0-6.0 pg/mL
13 years-20 years: 2.0-5.0 pg/mL
>21 years: 2.0-4.4 pg/mL
Day(s) Test Set Up
Monday through Sunday
Test Classification and CPT Coding
84481