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TSH with Reflex to Free T4 [36127X]

Test Code

361278

CPT Code(s)

84443

Includes

For patients 1 year of age or older, Free T4 will be performed at an additional charge (CPT code(s): 84439) when TSH result exceeds age/gender specific reference range.

Preferred Specimen(s)

1 mL serum

Minimum Volume

0.7 mL

Alternative Specimen(s)

1 mL plasma collected in a: sodium heparin (green-top) tube

Specimen Container

Plastic screw-top vial

Transport Temperature

Room temperature

Specimen Stability

Serum
 Room temperature: 7 days
 Refrigerated: 7 days
 Frozen: 28 days
Plasma
 Room temperature: 72 hours
 Refrigerated: 7 days
 Frozen: 28 days

Methodology

Immunoassay

Performing Laboratory

Quest Diagnostics Nichols Institute
14225 Newbrook Drive
Chantilly, VA 20153

Setup Schedule

Set up: Daily all shifts; Report available: Next day

Reference Range(s)

Premature Infants (28-36 Weeks)  
  1st Week of Life 0.20-27.90 mIU/L
Term Infants (>37 Weeks)  
  Serum or Cord Blood 1.00-39.00 mIU/L
  1-2 Days 3.20-34.60 mIU/L
  3-4 Days 0.70-15.40 mIU/L
  5 Days-4 Weeks 1.70-9.10 mIU/L
  1-11 Months 0.80-8.20 mIU/L
  1-19 Years 0.50-4.30 mIU/L
  ≥20 Years 0.40-4.50 mIU/L
Pregnancy  
  First Trimester 0.26-2.66 mIU/L
  Second Trimester 0.55-2.73 mIU/L
  Third Trimester 0.43-2.91 mIU/L
TSH levels decline rapidly during the first week of life in most children, but may remain transiently elevated in a few individuals despite normal free T4 levels. For proper interpretation of an abnormal TSH from a newborn thyroid screen, a Free T4 by Dialysis (test code 35167) or Total T4 (test code 867) should be considered.

Clinical Significance

For differential diagnosis of primary, secondary, and tertiary hypothyroidism. Also useful in screening for hyperthyroidism. This assay allows adjustment of exogenous thyroxine dosage in hypothyroid patients and in patients on suppressive thyroxine therapy for thyroid neoplasia.

LOINC®' Code(s)

The Result and LOINC information listed below should not be used for electronic interface maintenance with Quest Diagnostics. Please contact the Quest Diagnostics Connectivity Help Desk for more information at 800-697-9302.

NOTE: The codes listed in the table below are not orderable Test Codes.

Result
Code
Result NameLOINC CodeComponent Name
866T4, Free3024-7Thyroxine.free
899TSH3016-3Thyrotropin

Reference ranges are provided as general guidance only. To interpret test results use the reference range in the laboratory report.

The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.

LOINC assignment is based on a combination of test attributes, including the method used by the performing laboratory. For tests not performed by Quest Diagnostics, codes are assigned by the performing laboratory.

* The tests listed by specialist are a select group of tests offered. For a complete list of Quest Diagnostics tests, please refer to our Directory of Services.