Thyroid Cascading Reflex
Test Code
15102
84443
CPT Code is subject to a Medicare Limited Coverage Policy and may require a signed ABN when ordering.
Clinical Significance
Thyroid Cascading Reflex - The Thyroid Cascading Reflex order code that will act as an aid to physicians in the diagnosis of common adult thyroid disorders. The initial results of a TSH will determine further reflex orders of T4, Free, TPO Antibodies and T3, Free orders and provided an interpretation based upon the results of the reflexed tests.
Test Resources
Clinical Focus
Thyroid Dysfunction in Nonpregnant AdultsTest Details
The Thyroid Cascading Reflex begins with a TSH.
If the TSH result is abnormal, then T4, Free will be performed at an additional charge (CPT code(s): 84439).
If the TSH is elevated and the T4, Free is either normal or low, then TPO Antibodies will be performed at an additional charge (CPT code(s): 86376).
If the TSH is low and the T4, Free is either normal or low, then T3, Free will be performed at an additional charge (CPT code(s): 84481).
Note: This assay should only be ordered on patients 1 year of age or older. Orders on patients younger than 1 year will have a TSH only performed.
If the TSH result is abnormal, then T4, Free will be performed at an additional charge (CPT code(s): 84439).
If the TSH is elevated and the T4, Free is either normal or low, then TPO Antibodies will be performed at an additional charge (CPT code(s): 86376).
If the TSH is low and the T4, Free is either normal or low, then T3, Free will be performed at an additional charge (CPT code(s): 84481).
Note: This assay should only be ordered on patients 1 year of age or older. Orders on patients younger than 1 year will have a TSH only performed.
Specimen collection after fluorescein dye angiography should be delayed for at least 3 days. For patients on hemodialysis, specimen collection should be delayed for 2 weeks after angiography. According to the assay manufacturer Siemens: samples containing fluorescein can produce falsely depressed values.
Methodology
Immunoassay (IA)
Reference Range(s)
| Premature Infants (28-36 Weeks) | |
| 1st Week of Life | 0.20-27.90 mIU/L |
| Term Infants (>37 Weeks) | |
| Serum or Cord Blood | 1.00-39.00 mIU/L |
| 1-2 Days | 3.20-34.60 mIU/L |
| 3-4 Days | 0.70-15.40 mIU/L |
| 5 Days-4 Weeks | 1.70-9.10 mIU/L |
| 1-11 Months | 0.80-8.20 mIU/L |
| 1-19 Years | 0.50-4.30 mIU/L |
| ≥20 Years | 0.40-4.50 mIU/L |
| Pregnancy | |
| First Trimester | 0.26-2.66 mIU/L |
| Second Trimester | 0.55-2.73 mIU/L |
| Third Trimester | 0.43-2.91 mIU/L |
TSH levels decline rapidly during the first week of life in most children, but may remain transiently elevated in a few individuals despite normal free T4 levels. For proper interpretation of an abnormal TSH from a newborn thyroid screen, a Free T4 by Dialysis (test code 35167) or Total T4 (test code 867) should be considered.
Preferred Specimen(s)
4 mL serum
Minimum Volume
2 mL
Collection Instructions
This assay should only be ordered on patients 1 year of age or older. Orders on patients younger than 1 year will have a TSH only performed.
Transport Container
Serum separator tube (SST)
Transport Temperature
Room temperature
Specimen Stability
- Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days
Setup Schedule
4 mL serum
2 mL
This assay should only be ordered on patients 1 year of age or older. Orders on patients younger than 1 year will have a TSH only performed.
Serum separator tube (SST)
Room temperature
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days
Refrigerated: 7 days
Frozen: 28 days