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Additional Codes
LAB5725
Performing Laboratory
MBMC Main Laboratory
Methodology
Electro-Chemiluminescent Immunoassay (ECLIA)
Testing Algorithm
If the TSH result is outside of established reference range, a Free T4 will reflex with an additional charge. If the Free T4 result is < 1.7 ng/dL and the TSH is <0.3mcLUnits/mL, a Free T3 will reflex with an additional charge.
Specimen Requirements
Specimen Type: Plasma
Container/Tube: Mint-green top (lithium heparin)
Specimen Volume: Full tube
Specimen Minimum Volume: 2.5 mL
Alternative Specimen Type: Serum
Alternative Container/Tube: Gold, Serum gel
Alternative Specimen Volume: Full tube
Specimen Transport Temperature
Ambient
Day(s) Test Set Up
Monday through Sunday
Turnaround Time:
STAT: 1 hour after receipt in laboratory
Routine: within 4 hours
Reference Values
TSH:
0-4 days: 1.00 - 25.00 uIU/mL
4-30 days: 0.50 - 10.00 uIU/mL
>30 days: 0.30 - 4.20 uIU/mL
TSH concentration may range up to 100 mcIUnits/mL due to surge of TSH production on the first day of life and then fall gradually to adult levels by one month of age.
Free T4:
0 minutes-4 days 1.00 - 3.00 ng/mL
4 days-30 days 0.80 - 2.20 ng/mL
30 days-150 years 0.90 - 1.70 ng/mL
Free T4 concentrations rise acutely to as high as 5.00 ng/dL on the first day of life following TSH surge and then decrease gradually to adult levels by one month of age.
Free T3:
2.00-4.40 pg/mL
Test Classification and CPT Coding
Test Classification:This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer’s instructions.
CPT Code:
84443-TSH
84439-Free T4, if appropriate
84481-Free T3, if appropriate