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Test Code TSHFT4 Thyroid-Stimulating Hormone (TSH) with Reflex to FT4, Plasma or Serum

Performing Laboratory

MaineGeneral Medical Center

Specimen Requirements

Submit only 1 of the following specimens:

 

Preferred:

Plasma

Draw blood in a green-top (lithium heparin) tube(s). For pediatric specimen, draw blood in a green-top (lithium heparin) MICROTAINER(S)®. (Moderately hemolyzed specimen is not acceptable.) Spin down and send 1 mL of lithium heparin plasma refrigerated.

Note:  1. Indicate plasma on request form.

2. Label specimen with patient’s name (first and last), date of birth, date and time of draw, phlebotomist’s initials, and as plasma.

 

Alternate:

Serum

Draw blood in a serum gel tube(s). (Moderately hemolyzed specimen is not acceptable.) Spin down and send 1 mL of serum refrigerated.

Note:  1. Indicate serum on request form.

2. Label specimen with patient’s name (first and last), date of birth, date and time of draw, phlebotomist’s initials, and as serum.

Reference Values

TSH

0.3-4.8 mIU/L

Critical value (automatic call-back):  >100 mIU/L

Free T4

0.6-1.6 ng/mL

Critical value (automatic call-back):  >4.0 ng/mL

Methodology

Note:  If TSH is <0.3 mIU/L or >4.8 mIU/L, then a FT4 “T4 (Thyroxine), Free, Plasma or Serum” will be performed at an additional charge.

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding

84443 - TSH

84439 - FT4 (if appropriate)