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Test Code THCAS THYROID CASCADE

Important Note

TSH is performed first. If the TSH is outside the normal range, a T4, Free is ordered automatically (CPT: 84439). If the TSH is low and the T4, Free is normal based on the appropriate reference range for the age/sex of the patient, a T3, Total is ordered (CPT: 84480).

The results of this assay can be effected due to the consumption of Biotin. Patients should discontinue the use of vitamins or supplements that contain Biotin 12 hours before blood draw. 

 

Additional Codes

LAB2103

Performing Laboratory(s)

Porter Hospital Laboratory

University of Vermont Medical Center (T3 Total)

Specimen Requirements

Specimen Type: Blood
Container/Tube: Tiger top, serum gel
Specimen Volume: Full tube, submit 1.0 mL serum
Specimen Minimum Volume: 0.6 mL for full cascade
Collection Instructions:
1. Send specimen in original tube.
2. If there is a delay in transport of >1 hour, centrifuge tube.
3. Centrifuged samples are stable for:
• 7 days at 2 – 8ºC

Specimen Transport Temperature

Refrigerated

Test Classification and CPT Coding

TSH 84443

FT4  84439

T3    84480

Test Schedule / Analytical Time / Test Priority / Turn Around Time

Daily / 24 Hours / Available STAT / Routine - 4 Hours

                                                       STAT - 60 Minutes

(Total T3 will be sent to Reference Lab for testing if needed)

Normal Reference Values

See each component.

Critical Values

None

Components

TSH reflex 

Free T4 reflex

Total 3