Thyroxine, Free Direct Dialysis

Last Modified: 8/21/2023 2:22:03 PM


  Medicare Medical Necessity Restrictions May Apply
Medical Necessity Documentation:  
Client Notes:  
Patient Preparation:

Fasting patients preferred
Specimen Requirements:

2.0 mL Serum from a Red Top Tube in a Plastic Vial
Collection Instructions:  
Minimum Volume: 0.2 mL Serum
Transport & Storage: Temperature/Stability: 7 days Ambient
7 days Refrigerated
28 days Frozen
Reference Range: Pregnancy Reference Ranges
First Trimester: 0.9 - 2.0 ng/dL
Second Trimester: 0.8 - 1.5 ng/dL
Third Trimester: 0.8 - 1.7 ng/dL

Prematures, 25-30 weeks Birth to 7 days: 0.5 - 3.3 ng/dL
Prematures, 31-36 weeks, Birth to 7 days: 1.3 - 4.7 ng/dL
Cord Blood, > 37 weeks: 1.2-2.2 ng/dL
Birth to 4 days: 2.2 - 5.3 ng/dL
5 days to 13 days: Reference Range not established
2 weeks to 2 years: 0.8 - 2.0 ng/dL
3 years to 20 years: 1.0-2.4 ng/dL
21 years to 87 years: 0.8 - 2.7 ng/dL
> 87 years: Reference Range not established 
Critical Ranges:  
Test Comments: This assay utilizes biotin technology. Patients taking vitamin supplements containing high doses of biotin (>5 mg/day) may have falsely increased test results generated.
Methodology: Radioimmunoassay Direct Equilibrium Dialysis
Clinical Significance:  
Documentation:  
Custom Panel: No

PRODUCTION SCHEDULE

Turn Around Time: 4 to 7 days
Days Performed: Monday, Tuesday, Wednesday, Thursday
Sites Performed: Quest - Chantilly
PHL Test Code: T4FR
EPIC Test Code: LAB2518
Send Out Test Code: 35167
Alternate Test Names: Free T4 Direct Dialysis; FT4 Direct Dialysis; T4 Free Direct Dialysis; T4 Free Eq Dialysis
Included Tests:  
CPT Coding: 84439

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