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Test Code 8234 Thyroid-Stimulating Hormone Cascade

Important Note

The Thyroid cascade is a reflex test where the reflex is part of the order and there is no option to decline the testing. TSH is done first. If the TSH is outside normal range a Free-T4 is ordered automatically (CPT: 84439). If the TSH is low and the Free-T4 is normal based on the appropriate reference range for the age/sex of the patient a Total -T3 is ordered (CPT: 84480).

Test subject to Medicare National Coverage Determination (NCD) 190.22 THYROID TESTING

See Medical Necessity on Sidebar

Purpose

Thyroid function test. Investigation of low thyroxine (T4) result; the differential diagnosis of primary hypothyroidism from normal, and the differential diagnosis of primary hypothyroidism from pituitary/hypothalamic hypothyroidism. TSH is high in primary hypothyroidism. Low TSH occurs in hyperthyroidism.

 

Performing Laboratory

Copley Hospital

 

Methodology

Chemiluminescence (LOCI Module)

 

Specimen Requirements

Specimen Type: Blood (Plasma or Serum)

Preferred: Light-Green Top

Acceptable: Gold Top

Specimen Volume: Full Tube

Specimen Minimum Volume: 2 mL

 

Collection Instructions:

1. Label specimen with patient’s full name, date of birth,

    date & time of collection and person collecting.

2. If delay in specimen transport > 1 hour, centrifuge tube.

3. Refrigerate specimen during transport.

 

Reference Values

Normal: 0.36 - 3.74 µIU / mL

 

Stability

Refrigerated: 7 Days

 

Day(s) Performed

Daily

Available STAT

Analytical Time: 1 Day

 

Aliases

Thyroid-Stimulating Hormone Cascade

TSH Cascade

Thyroid-Stimulating Hormone

Free T4

Thyroxine

TSH

 

Test Classification & CPT Coding

84443