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Test Code LAB123676 TSH Cascade

Important Note

Note 1: Order this test if an order for "TSH with reflex to Free T4 (FT4)" is requested.

Note 2: A.K.A. Thyroid Cascade

Note 3: Testing requires both plasma (light green tube) and serum (plain red tube).

Caution:

Two important patient groups may require alternate thyroid function testing strategies: patient with pituitary disease and patients patients with neuropsychiatric disorders.  These patients may require endocrinologic consultations, because the sensitive-thyroid stimulating hormone measurement may be misleading and additional tests probably are necessary.

Methodology

Profile Information:

Test ID

Reporting Name

Available Separately

TSH

TSH, Sensitive, S

Yes

Reflex Tests:

Test ID

Reporting Name

Available Separately

FT4

T4 (Thyroxine), Free, S

Yes

ATPO

Thyroperoxidase Ab, S

Yes

T3R

T3 (Triiodothyronine), Total, S

Yes

Performing Laboratory

Peninsula Regional Medical Center - Chemistry and Special Chemistry

Specimen Requirements

Testing requires both plasma (light green tube) and serum (plain red tube).

1 - Light Green

Draw blood in a green-top (lithium heparin) tube.

Spin down and send 2 mL of lithium heparin plasma.

Label specimen as Plasma.

1- plain red

Draw blood in a plain, red-top tube.  

Spin down and send 2 mL of serum.  

Label specimen as Serum. 

Reference Values

≥18 years: 0.450-5.330 µIU/mL

Reference values have not been established for patients that are <12 months of age.

Day(s) Test Set Up

Monday through Sunday

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)

Additional Information

Testing Algorithm:
If thyroid-stimulating hormone (TSH) is <0.450 µIU/mL, then free T4 (FT4) is performed at an additional charge.

If FT4 is normal and the TSH is <0.1 µIU/mL, then T3 is performed at an additional charge.

If TSH is >5.330 µIU/mL, then FT4 and thyroperoxidase antibodies are performed at an additional charge. Note: Thyroperoxidase antibodies will only be reflex ordered if the patient has no history of abnormal thyroperoxidase antibodies testing.