Test Details
Methodology
Equilibrium dialysis and high-pressure liquid chromatography/tandem mass spectrometry (HPLC/MS-MS)
Result Turnaround Time
6 - 10 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Custom Additional Information
Direct measurement of FT3 by equilibrium dialysis, high-pressure liquid chromatography, and tandem mass spectrometry (ED-HPLC/MS-MS) provides enhanced accuracy over commonly used analog (automated) methods and is not affected by clinical conditions that impact protein binding capacity.1-4 Examples of clinical conditions in which the FT3 by dialysis and MS/MS method may be preferred include congenital absence of thyroxine-binding protein (TBG);1 pregnancy;1-5 administration of oral contraceptives or hormone therapy;6 administration of atypical antipsychotic medications;7 malignancy or other critical illnesses.8
Specimen Requirements
Specimen
Serum (preferred) or plasma, frozen
Volume
1 mL
Minimum Volume
0.3 mL (Note: This volume does not allow for repeat testing).
Container
Red-top tube, gel-barrier tube, lavender-top (EDTA) tube, or green-top (sodium heparin) tube
Collection Instructions
Serum/plasma must be separated from cells within 45 minutes of venipuncture. Send serum/plasma in a plastic transfer tube.
Reference Range
See table.
Age | Range (pg/mL) | Mean (pg/mL) |
|---|---|---|
Premature (0 to 4 wk) | 1.35−6.25 | 3.13 |
Newborn | ||
0 to 2 wk | 0.99−8.03 | 4.21 |
2 wk to 12 m | 1.59−6.15 | 3.87 |
Prepubertal 1 to 10 y | 2.21−4.99 | 3.60 |
Children >10 y and adults | 1.81−4.06 | 2.77 |
Pregnant female | ||
first trimester | 1.6−3.3 | 2.5 |
second trimester | To be determined | |
third trimester | 1.0−3.2 | 2.1 |
Storage Instructions
Freeze (preferred) or refrigerate. Stable at room temperature or refrigerated for five days. Stable frozen for 70 days.
Causes for Rejection
Whole blood
Footnotes
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 503600 | T3, Free, Dialysis, LC/MS-MS | 503601 | T3, Free, Dialysis, LC/MS-MS | pg/mL | 29239-1 | |
| Order Code | 503600 | |||||
| Order Code Name | T3, Free, Dialysis, LC/MS-MS | |||||
| Order Loinc | ||||||
| Result Code | 503601 | |||||
| Result Code Name | T3, Free, Dialysis, LC/MS-MS | |||||
| UofM | pg/mL | |||||
| Result LOINC | 29239-1 |