Table 1.

Reference ranges for thyroid function assays with their associated intra-assay coefficient of variation

Test	Reference range	Intra-assay coefficient of variation, associated range (95% CI)
Thyroid-stimulating hormone (TSH)	0.3–4.5 mlU/L	1.5% (0.5 to 33.0 mlU/L)
Free thyroxine (FT4)	10–22 pmol/L	2.0–2.5% (9.0 to 66.0 pmol/L)
Free triiodothyronine (FT3)	3.1–6.8 pmol/L	2.0–3.5% (4.0 to 21.0 pmol/L)