Test/Investigation
Free triiodothyronine (fT3)
Site(s) or Laboratory offering Test/Investigation
NNUH, QEH, JPUH
Units
pmol/L
Comments/Precautions
May be added to thyroid profile. Used to monitor treatment of thyrotoxicosis in first few months post diagnosis. Occasionally for detection of T3 toxicosis (free T4 and TSH suppressed). Please contact the lab if you suspect assay interference
Sample type
Serum
Turnaround times (TAT) Urgent/Routine/GP or OPD
1 hour / 4 hour / by 8am next day
Reference intervals (adult unless stated)
Adult (> 18 yr) range: 2.4 – 6.0 pmol/L
Female paediatric ranges:
4 day – < 1yr 3.56 – 7.48 pmol/L
1 yr – < 12 yr 4.29 – 6.79 pmol/L
12 yr – < 15 yr 3.84 – 6.06 pmol/L
15 yr – < 19 yr 3.55 – 5.7 pmol/L
Male paediatric ranges:
4 day – < 1yr 3.56 – 7.48 pmol/L
1 yr – < 12 yr 4.29 – 6.79 pmol/L
12 yr – < 15 yr 4.44 – 6.65 pmol/L
15 yr – < 19 yr 3.46 – 5.92 pmol/L
If UKAS Accredited Test indicate at which site
Y NNUH, QEH
Source
Adult ranges: Abbott Alinity kit insert [G71299R04] Paediatric ranges: CALIPER (Adeli, K., Higgins, V., Trajcevski, K., White-Al Habeeb, N. (2017). The Canadian laboratory initiative on pediatric reference intervals: A CALIPER white paper. Crit Rev Clin Lab Sci, 54(6):358-413. doi: 10.1080/10408363.2017.1379945. Epub 2017 Oct 11. Erratum in: Crit Rev Clin Lab Sci. 2020 Mar;57(2):145. PMID: 29017389.)