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Test Code THYCASC Thyroid Function Cascade

Important Note

1. If thyroid-stimulating hormone (TSH) is <0.1 mIU/L, then free T4 (FT4) is performed at an additional charge. If FT4 is normal and the TSH is <0.1 mIU/L, then T3 is performed at an additional charge.

2. If thyroid-stimulating hormone (TSH) is 0.10-0.29 mIU/L, then free T4 (FT4) is performed at an additional charge.

3. If thyroid-stimulating hormone (TSH) is 0.30-4.2 mIU/L, no further testing will occur.

4. If thyroid-stimulating hormone (TSH) is >4.2 mIU/L, then free T4 (FT4) and Thyroperoxidase (TPO) will be performed at an additional charge.

All Reflex testing is performed at Beebe Healthcare Laboratory except for Thyroperoxidase (TPO) which is performed by Mayo Medical Laboratories.

Additional Codes

TSH

Thyroid Stimulating Hormone

FT4

Free T4

Free Thyroxine

FT3

Free Triiodothyronine

TPO

Thyroperoxidase

 

Specimen Requirements

You must collect both specimens:

 

TSH, FT4 and FT3

Container/Tube Type: Green Top (Lithium Heparin) Tube

Transport refrigerated.

 

 

TPO:

Patient Preparation: Twelve hours before this test, do not take multivitamins or dietary supplements containing biotin or vitamin B7 that are commonly found in hair, skin, and nail supplements and multivitamins.

Container/Tube: Red top

Specimen Volume: 0.6 mL

Collection Instructions: Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.

 

TPO Minimum Volume: 0.5 mL serum

Day(s) Test Set Up

Monday through Sunday; Continuously

Test Classification and CPT Coding

84443-Thyroid-stimulating hormone-sensitive (s-TSH)

84439-T4 (thyroxine), free (if appropriate)

84480-T3 (triiodothyronine), total (if appropriate)

86376-Thyroperoxidase (TPO) antibodies (if appropriate)

Performing Laboratory

Beebe Healthcare Laboratory

Mayo Medical Laboratories (If TPO performed)

Performing Location

Margaret H. Rollins Laboratory
South Coastal Campus Laboratory

Rochester, Minnesota - Mayo Test (if applicable)

Specimen Stability

For TPO:

Specimen Type Temperature Time
Serum Refrigerated (preferred) 7 days
  Frozen  30 days
  Ambient  72 hours

 

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