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Mint Green Top (Lithium Heparin Gel)
Specimen Requirements
Preferred:
Container/Tube: Mint Green Top (Lithium Heparin Gel)
Minimum Volume: 1.0 mL
Collection Instructions: Centrifuge within 2 hours
Also Acceptable:
Container/Tube: Gold Top (SST-Gel)
Specimen Stability
Ambient: 8 hours
Refrigerate: 48 hours
Frozen: aliquot for longer storage
Reference Range
0-10 years: 0.60-1.34 ng/dL
11-18 Years: 0.50-1.25 ng/dL
19+ years: 0.61-1.12 ng/dL
Reference Ranges for Pregnant Females:
Pregnant Females, 1st Trimester 0.52 – 1.10 ng/dL
Pregnant Females, 2nd Trimester 0.45 – 0.99 ng/dL
Pregnant Females, 3rd Trimester 0.48 - 0.95 ng/dL
Methodology
Chemiluminescent Immunoassay
CPT
84439
Interferences
Biotin concentrations > 10 ng/mL can lead to
significant (> 10%) positive bias in Free T4 results.
If unexpected results are obtained, and biotin
interference is suspected, the Beckman Coulter TSH assay may provide a better assessment of thyroid function as it is not susceptible to biotin interference.