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Test Code CTSH3 TSH Cascade

Important Note

An algorithm is used to reflex testing based on the initial TSH result.  See attached algorithm in Resources section.

Additional Codes

EPIC:  LAB5431

Methodology

Chemiluminescent Immunoassay

Functional sensitivity: 0.01 mIU/mL


Used in the differential diagnosis of primary (thyroid) from secondary (pituitary) and tertiary (hypothalamus) hypothyroidism, in the diagnosis of primary hyperthyroidism, and in monitoring patients on thyroid replacement therapy.

Performing Laboratory

St. Joseph Hospital

Specimen Requirements

Serum

Draw blood in a plain, red-top tube or a serum gel tube. (Hemolyzed specimen is not acceptable.) Centrifuge and separate serum from cells within 2 hours of collection and send 1 mL of serum refrigerated.

 

Reference Values

TSH:  0.270 - 4.700 µIU/mL

FT4:  0.9 - 1.7 ng/dL

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding

84443

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