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Test Code T4 T4, LAB126


Homogeneous Enzyme Immunoassay (EIA)

Performing Laboratory

St. Luke's Hospital Cedar Rapids

Specimen Requirements


Prefered:  Green-top (lithium heparin) tube

Acceptable:  Gold-top serum gel tube or plain, red-top tube

Specimen Volume: 0.1 mL of plasma or serum

Stability:  Separated samples stored at 2 – 8°C and analyzed within 30 days

Collection Instructions:

Note: 1. Anti-thyroxine antibodies will interfere with this assay.

2. Human anti-mouse antibodies or other heterophile antibodies may be present in patient specimens. This assay has been specially formulated to minimize the effects of these antibodies, however results from patients known to have these antibodies should be carefully evaluated.

Reference Values


Age Group



1 – 23 months

7.4 – 14.3 mcg/dL


2 years – 12 years

6.8 – 12.5 mcg/dL


13 years – 20 years

6.0 – 11.6 mcg/dL


≥21 years

4.7 – 13.3 mcg/dL


Day(s) Test Set Up

Monday through Saturday

Test Classification and CPT Coding


Useful For

Thyroid funtion