Table 2.

Reference interval of FT4 (pmol/L)

	First trimester	Second trimester	Third trimester	Post-partum
Sample size	139	139	139	55
Mean + 2SD
Lower limit	11.39	9.98	9.48	11.97
90% CI	11.09–11.70	9.71–10.24	9.19–9.80	11.53–12.43
Upper limit	17.39	15.25	15.10	19.10
90% CI	16.96–17.84	14.86–15.65	14.71–15.49	18.06–20.26
Percentile non parametric method
Lower limit	11.35	9.79	9.48	11.95
90% CI	10.08–12.14	9.24–10.3	8.20–10.12	–*
Upper limit	17.35	15.47	15.37	19.25
90% CI	16.80–19.05	14.88–16.90	14.43–16.25	–*
Robust method
Lower limit	11.35	9.96	9.46	11.88
90% CI	11.06–11.67	9.68–10.25	9.16–9.77	11.50–12.33
Upper limit	17.43	15.30	15.13	19.29
90% CI	16.96–17.89	14.90–15.70	14.73–15.54	18.22–20.38

–*Not calculated, as recommended by CLSI document EP28-A3c [16]