Thyroid Cascading Reflex
Test code
CPT code(s)*
Test resources
Clinical focus
Details
Includes
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.
Methodology
Immunoassay (IA)
Specimen requirements | |
|---|---|
| Patient preparation | 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. |
| 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 |
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.
Reference ranges are provided as general guidance only. To interpret test results use the reference range in the laboratory report.
*The CPT codes provided are based on AMA guidance 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.
This material contains content from LOINC® (http://loinc.org). The LOINC Table, LOINC Table Core are copyright © 1995-2019, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee and is available at no cost under the license at http://loinc.org/license.
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