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HelpTest Code FT4 Free Thyroxine (FT4)
Laboratory Code
LAB127
Specimen Requirements
Specimen Type: Serum
Container/Tube: Gold Top (SSTII)
Volume: 5.0 mL
Minimum Volume: 0.5 mL serum
Collection Instructions: Allow specimen to clot for 30 mins and centrifuge within 2 hrs.
Specimen Stability
| Specimen Type | Serum |
|---|---|
| Ambient | 24 hours |
| Refrigerate | 6 days |
| Frozen | 1 month |
Methodology
Chemiluminescent Immunoassay
Days and Times Performed
24 hrs, TAT 1 day
Specimen Condition
| Gross Haemolysis | Alert/Reject |
|---|---|
| Icterus | OK |
| Lipaemia | OK |
| Others | Not applicable |
Reference Interval
| Age | |
|---|---|
| 0 – < 1 yr | 10.5 – 18.8 pmol/L |
| 1 yr – 18 yrs | 10.0 – 14.3 pmol/L |
| ≥ 19 yrs | 9.0 – 19.1 pmol/L |
Testing Laboratory
National University Hospital
Clinical Chemistry, 67724346
Useful For
Diagnosis of hyperthyroidism and hypothyroidism.
Service Code
31623
LOINC Code Information
83121-4
Alias
Free T4 (Thyroxine)
Non-Protein Bound Tetraiodothyronine
Update
Last updated 11/03/2025