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Thyroxine (T4), Free, Dialysis/Mass Spectrometry (Endocrine Sciences)

CPT: 84439
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Synonyms

  • Free Thyroxine (T4) by Dialysis/Mass Spectrometry

Expected Turnaround Time

6 - 11 days



Specimen Requirements


Specimen

Serum or plasma


Volume

1 mL


Minimum Volume

0.5 mL; pediatric volume: 0.4 mL (Note: This volume does not allow for repeat testing.)


Container

Red-top tube, gel-barrier tube, or lavender-top (EDTA) tube


Collection

Serum or plasma must be separated from cells within 45 minutes of venipuncture. Send serum or plasma in plastic transport tube. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.


Storage Instructions

Freeze


Stability Requirements

Temperature

Period

Room temperature

2 days

Refrigerated

5 days

Frozen

453 days

Freeze/thaw cycles

Stable x3


Test Details


Methodology

Direct dialysis mass spectrometry; high-pressure liquid chromatography/mass spectrometry (HPLC/MS)


Reference Interval

See table.

Age

Range (ng/dL)

Premature (0 to 4 wk)

0.86−4.46

Newborn

0 to 2 wk

0.84−4.97

2 wk to 12 m

0.81−2.12

Children 1 to 11 y

0.65−1.9

Pubertal children and adults

0.8−1.7

Pregnant female

first trimester (0 to 13.3 wk)

0.65−1.4

second trimester (13.4 to 26.6 wk)

0.5−1.3

third trimester (>26.6 wk)

0.5−1.1


LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
501902 Free T4 by Dialysis/Mass Spec 501903 Free T4 by Dialysis/Mass Spec ng/dL 6892-4

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