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Specimen Collection Manual and Test Catalog

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TSH WITH FREE T4 IF INDICATED

Geisinger Epic Procedure Code:  LAB3206    Geisinger Epic ID:  41920

SPECIMEN COLLECTION
Specimen type: 

Plasma or serum


Preferred collection container: 
Alternate collection container: 
3 mL green/black top lithium heparin tube
Specimen required: 

2 mL plasma or serum; minimum 0.5 mL



SPECIMEN PROCESSING
Processing instructions: 

Allow serum to clot. Centrifuge to separate serum or plasma within 2 hours of collection.


Transport temperature: 

Refrigerated (preferred) or frozen.


Specimen stability: 

Refrigerated: 7 days. Frozen: 1 month.


Rejection criteria: 

Stability limits exceeded.



TEST DETAILS
Reference interval: 

TSH: 0.27-4.2 uIU/mL
Free T4: 0.9 - 1.7 ng/dL.


Additional information: 

Specimens containing human anti-mouse antibodies may affect results.


CPT code(s):  84443
Note: The billing party has sole responsibility for CPT coding.  Any questions regarding coding should be directed to the payer being billed.
The CPT codes provided by GML are based on AMA guidelines and are for informational purposes only.

Test includes: 

Thyroid stimulating hormone (TSH) with an add-on of “Free T4” if the TSH is abnormal.


Methodology: 
Electrochemiluminescence
Synonyms: 

Thyroid Stimulating Hormone w/Free thyroxine if Thyroid Stimulating Hormone is abnormal, TSHR


Clinical significance: 

Typically, a small change in free T4 is accompanied by a big change in TSH. Thus, abnormal TSH levels often occur before free T4 abnormalities are detectable. This makes the “TSH w/FT4 if TSH is abnormal” test most suitable for screening for primary thyroid dysfunction and evaluation of thyroid nodule.


Doctoral Director(s): 
Hoi-Ying Elsie Yu, PhD, DABCC, FADLM
Sheng-Ying (Margaret) Lo, PhD, DABCC
Review Date:  12/27/2024

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