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Test Code TFC or LAB2346 Thyroid Function Cascade (TFC) Panel, Serum or Plasma

Important Note

The Thyroid Function Cascade (TFC) algorithm is designed for patients 6 years or older for initial screening and diagnosis of thyroid disease in non-hospitalized patients.

If an order for TFC is received on younger patients, TSH and Free T4 will be performed. If indicated, additional tests would need to be requested by the ordering physician. 

Please note: The screening cascade is not designed for monitoring patients receiving thyroid replacement therapy. For monitoring such patients, TSH should be followed 6-8 weeks after a dose change and every 6-12 months in patients on stable doses of thyroid replacement therapy.

Specimen Requirements

Container Type:

Optimal: Gold or Mint*

*For STAT requests

Acceptable: Red or Green
Optimal Collection Volume: 

4.5mL; full tube
Minimum Volume:

1 mL whole blood
Collection Instructions:

Gently invert the sample 5-6 times after collection.
Specimen Transport:

Refrigerate
Processing Instructions: 

1. If serum, allow the specimen to clot for 30 minutes.

2. Centrifuge specimen within 2 hours of collection.

3. After centrifugation, specimen tubes without a gel barrier should have the serum or plasma aliquoted to a false bottom container.

4. Keep serum or plasma refrigerated until testing can be performed.

Specimen Stability

Specimen Type Temperature Time
Serum* Refrigerated 7 days
Room Temperature 7 days
Frozen 30 days

*Note: Heparinized plasma in gel separator tubes is less stable than serum and is only suitable for add-on testing up to 2 days following sample collection.

Specimen Rejection Criteria

Hemolysis Mild OK; Moderate OK; Gross Reject
Lipemia Mild OK; Moderate OK; Gross Reject
Icterus Mild OK; Moderate OK; Gross Reject
Other Quantity not sufficient

Useful For

Screening for a diagnosis of thyroid disease.

Methodology

Roche Cobas - Electrochemiluminescence assay

Reference Ranges

Please click the Thyroid Function Cascade.

Day(s) Performed

24/7

Expected TAT

Same day

Performing Laboratory

Test

Performing Laboratory

BMH

BBC

BLH

BSH

TSH

X

X

X

X

Free T4

X

X

X

X

Total T3

X

      

Anti-TPO

X

      

* = If indicated, see Thyroid Function Cascade for details.

 

Sample Retention Time

6 days

CPT Code

  • TSH: 84443 (always performed)
  • Free T4: 84439*
  • Total T3: 84480*
  • Thyroid Peroxidase Antibody: 86376*

* = If indicated

LOINC Code

11579-0