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Test Code LAB136 T3 (Triiodothyronine), Total, Plasma or Serum

Additional Codes

46588

Reporting Title

T3 Total

Methodology

Roche Diagnostics, Electrochemiluminescence Immunoassay

T3 levels tend to distinguish euthyroid from hyperthyroid patients but are less clear in euthyroid and hypothyroid. T3 is most useful in diagnosing thyrotoxicosis and in monitoring sodium liothyronine therapy.

Performing Laboratory

OhioHealth Laboratory Services - RMH and MH Core Laboratories

Specimen Requirements

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. Heterophile antibodies may interfere with this assay.

3. Indicate serum on request form.

4. 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. Heterophile antibodies may interfere with this assay.

2. Indicate plasma on request form.

3. Label specimen appropriately (plasma).

 

Specimen Transport Temperature

Refrigerate/Frozen OK/Ambient OK

Reference Values

0-5  days:  73-288
6d-2 mo:   80-275
3-11 mo:   86-265
1-5 y:        92-248
6-10 y:      93-231
11-19 y:    91-218

>19 y:       72-170 ng/dL

 

Many conditions unrelated to thyroid disease affect T3 values, therefore, total T3 should not be used on its own to determine thyroid status. Other thyroid markers and clinical findings should be used as well. More than 20% of critically ill patients have low total T3 levels.

Day(s) Test Set Up

Monday through Sunday; Continuously

Test Classification and CPT Coding

84480