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Test Code FREE T4 Thyroxine Free

Clinical System Name

Thyroxine Free

Synonyms

FT4

Description

This method measures free T4 by competitive immunoassay. Free T4's with results of 0.6 or 0.7 ng/dL are sent out reflexively for Free T4 by equilibrium dialysis. 

Sample Requirements

Specimen: Whole blood

Container(s): Gold SST, Red, Gold Microtainer

Preferred Vol: 1.0 mL

Minimum Vol: 0.5 mL

 

 

Processing Instructions

Reject due to: gross lipemia

Spin: Y

Aliquot: Y

Temp: 2-8 C

Storage location: CPA refrigerator,  FrigD rack. Serum should be removed from separator for storage.

Note: Minimum volume of 1.0 mL serum may be shared with TSH, T3, T4, free T3, and free T4

 

Off-site collection: Spin blood. Transfer serum to plastic aliquot container. Refrigerate.

Stability

Specimen Type Temperature Time
gel separator with serum Refrigerated 48 h
separated serum Room temp 2 h
  Refrigerated 7 d
  Frozen -20 C 4 w

 

Availability

STAT Performed TAT
N M-Sa, day shift 1-3 d

 

Performing Laboratory

Seattle Children's Laboratory    

Department

Department:  Chemistry

Location: Chem West

Phone Number:  (206) 987-2617

 

 

 

Reference Range

  Age 

ng/dL

Birth - 3 days  2.0 - 5.0 
3 days - 1 month 0.9 - 2.2
1 month - 18 years 0.8 - 2.0
18 years - adult 0.8 - 2.2

 

Methodology

Method: Chemiluminescence by Vitros 3600, third generation assay

Analytical Volume: 0.200 mL serum

Limitations: Turbidity may affect results. Bilirubin 20 mg/dL causes positive interference of 20%.  Bilirubin less than 0.4 mg/dL is ok.

CPT Codes

84439