Free T4 (FT4)

Department: Chemistry
Test Synonym(s): LAB127, FT4, Thyroxine Free, Free Thyroxine
CPT Codes: 84439
Methodology: Chemiluminescent Microparticle Immunoassay (CMIA)
Reference Range: 5-14 days: 1.05-3.21 ng/dL; 15-30 days: 0.68-2.53 ng/dL; 1 mo-1 yr: 0.89-1.7 ng/dL; 1-150 yrs: 0.89-1.37 ng/dL; Pregnant Females - 1st Trimester: 0.88-1.46 ng/dL, 2nd Trimester: 0.72-1.22 ng/dL, 3rd Trimester: 0.66-1.10 ng/dL Note: Pediatric Reference Ranges only verified for serum, see CALIPER Study at CaliperDatabase.com
Tube Type: Gold top SST (Clot activator with gel)
Specimen: Serum
Alternate Specimen: Red Top (no gel)
Pediatric Requirements: 1 Gold top microtainer
Volume: 1 mL
Minimum Volume: 1 Gold top
Temperature: Separate within one hour and store at 2-8C until delivery
Stability: Room temperature: 1 day; Refrigerated: 6 days; Frozen: Not recommended
Reasons for Rejection: Hemolysis; improper collection
Days Performed: Daily
Times Performed: Continuous
Significance: NOTE: Pediatric Reference Ranges based on in-house studies and CALIPER database - CaliperDatabase.com
Special Instructions: Effective 5/29/18, the acceptable tube type for FT4 testing is Gold Top tube.

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