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HelpTest Code TFC Thyroid Function Cascade
EHR Test Codes
| Test Code | Test Name | |
| Atlas | TFC | Thyroid Function, Cascade |
| Cerner | TFC | Thyroid Function Cascade |
Specimen Requirements
Preparation of Patient:
None
Container Type:
Green Top 5mL Lithium Heparin Separator Tube
Or
Gold Top 6mL SST Gel & Clot Activator Tube
Specimen Type:
Plasma or Serum
Specimen Volume:
2.5 mL Plasma or Serum minimum .5 mL
Specimen Handling/Transport:
Separate plasma or serum from cells within 2 hours of collection.
Transport ambient room temperature.
Specimen Stability/Storage:
5 days refrigerated 2-8°C
Performing Laboratory
Munson Medical Center Laboratories
Chemistry Department
Priority, Frequency, & Turnaround
Priority:
Non-Emergent
Frequency:
24 hours 7 days a week
Turnaround:
0 - 1 days
Methodology
Chemiluminescence Immunoassay
Reporting
Reference Range:
TSH 0.45 - 5.33 µIU/mL
Reflex Testing: If TSH result is ≤0.45 mIU/L, then (FT4) Free T4 will be performed. If TSH result is ≥5.33 mIU/L, then (FT4) Free T4 and (TPO) Thyroperoxidase Antibodies will be performed.
Critical Decision:
None
Clinical Significance
Testing begins with a measurement of TSH. When the TSH concentration is elevated, additional tests for free thyroxine concentration (FT4) and Thyroperoxidase antibodies (TPO) are automatically performed on the same sample. When the TSHS concentration is low, the FT4 concentration is perfomed.
By utilizing a cascaded testing procedure to efficiently evaluate and monitor the functional thyroid status, previous results and follow-up information are provided without delay and inconvenient reordering also by beginning with TSH measurement, clinically insignificant binding protein problems are bypassed, and biochemical tests correlate better with the patient's physiologic thyroid function.
See TSH, FT4, and TPO test for more information.
CPT Code(s)
84443 - TSH
84439 - Free T4 (if performed)
86376 - TPO Antibodies (if performed)