Thyroid Cascading Reflex

Cleveland HeartLab T, Test


CPT Code:
Thyroid Stimulating Hormone (TSH):
     Thyroxine (T4), Free: 84439 (if reflexed)
     Thyroid Peroxidase Antibodies (TPO): 86376 (if reflexed)
     Triiodothyronine (T3), Free: 84481 (if reflexed)

Order Code: 1394
Tests Included: The Thyroid Cascading Reflex begins with a TSH. If the TSH result is abnormal, T4, Free will be performed at an additional charge (CPT Code: 84439). If the TSH is elevated and the T4, Free is either normal or low, TPO Antibodies will be performed at an additional charge (CPT Code: 86376). If the TSH is low and the T4, Free is either normal or low, T3, Free will be performed at an additional charge (CPT Code: 84481).

ABN Requirement: No
Specimen: Serum
Volume:  4.0 mL
Minimum Volume:  2.0 mL
Container: Gel-barrier tube (SST)


  1. Collect and label sample according to standard protocols.
  2. Gently invert tube 5 times immediately after draw. DO NOT SHAKE.
  3. Allow blood to clot 30 minutes.
  4. Centrifuge for 10 minutes.

Note: This assay should only be ordered on patients 4 years of age or older. Orders on patients younger than 4 years of age will only have a TSH performed.

Additional Information: Serum TSH levels exhibit a diurnal variation with the peak occurring during the night. The lowest levels occur between 10 AM and 4 PM and can reach 50% of the peak. Specimens should not be taken from patients receiving therapy with high biotin doses (>5 mg/day) until at least 8 hours following the last dose.

Transport: Store serum at 2°C to 8°C after collection and ship the same day per packaging instructions included with the provided shipping box.


Ambient (15-25°C): Not Acceptable
Refrigerated (2-8°C):
7 days
Frozen (-20°C):
30 days

Causes for Rejection: Specimens other than serum; improper labeling; samples not stored properly; samples older than stability limits; moderate or gross hemolysis; samples which are heat-inactivated; samples stabilized with azide

Methodology: Electrochemiluminescence Immunoassay (ECLIA)

Turn Around Time: 1 to 5 days

Reference Range(s) and/or Risk Range(s): See Laboratory Report or individual tests for reference range and/or risk range information

Thyroid Stimulating Hormone (TSH):

Thyroxine (T4), Free:

Thyroid Peroxidase Antibody (TPO):

Triiodothyronine (T3), Free:

Clinical Significance: The Thyroid Cascading Reflex is intended to aid physicians in the diagnosis of common adult thyroid disorders. The initial results of a TSH will determine further reflex orders of Free T4, TPO Antibodies, and Free T3 and will provide an interpretation based upon the results of the reflexed tests.

Limitations: The presence of autoantibodies may induce high molecular weight complexes (macro-TSH) which may cause unexpected high values of TSH. In rare cases, interference due to extremely high titers of antibodies to analyte-specific antibodies, streptavidin, or ruthenium can occur.

The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.