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HelpTest Code TSH Thyroid-Stimulating Hormone (TSH), Reflexive
Additional Codes
St. Luke's Compendium Code (Iatric): L303.1009
Performing Laboratory
St. Lukes Hospital Laboratory
Methodology
Testing Algorithm if reflexive question is answered with a "Y":
If TSH is <0.350 mIU/mL, then FT4 “T4 (Thyroxine), Free, Serum” and FT3 “T3 (Triiodothyronine), Free, Serum” will be performed at an additional charge.
If TSH is >4.800 mIU/mL, then FT4 “T4 (Thyroxine), Free, Serum” will be performed at an additional charge.
Method Name:
Two-Site Immunoenzymatic Immunoassay
Specimen Requirements
Tightly cap and refrigerate specimens at 2–8°up to 48 hours.
Freeze samples at ≤ -20°C up to 30 days.
Draw blood in a serum gel tube(s), preferred. Plasma from a lithium heparin is acceptable.
Spin down and send 1 mL of serum (or plasma) refrigerated. If specimen testing is delayed more than 48 hours, the specimen should be frozen in a plastic vial.
Unspun specimens must be transported at ambient temperature and arrive to the laboratory within one hour of draw.
Reference Values
TSH
0.350-4.800 µIU/mL
FREE T3
2.30-4.20 pg/mL
FREE T4
0.89-1.76 ng/dL
Day(s) Test Set Up
Monday through Sunday
Test Classification and CPT Coding
CPT:
84443 - TSH
84439 - FT4 (if appropriate)
84481 - FT3 (if appropriate)
LOINC:
11579-0-TSH
3024-7- FT4 (if appropriate)
3051-0-FT3 (if appropriate)