Accurate interpretation of thyroid dysfunction during pregnancy: should we continue to use published guidelines instead of population-based gestation-specific reference intervals for the thyroid-stimulating hormone (TSH)?

Table 5 Comparison between ATA and 6 subgroup-specific reference intervals

Subgroup	No. of subjects	Prevalence of thyroid dysfunction based on two criteria, n (%)		Prevalence of hyporthyroidism based on two criteria, n (%)		Prevalence of hyperthyroidism based on two criteria, n (%)		Kappa value	P value
Subgroup	No. of subjects	Subgroup-specific^a	ATA guidelines^b	Subgroup-specific^a	ATA guidelines^b	Subgroup-specific^a	ATA guidelines^b	Kappa value	P value
T1_a	245	29 (11.8)	49 (20.0)	14 (5.7)	47 (19.2)	15 (6.1)	2 (0.8)	0.33	< 0.001
T1_b	460	69 (15.0)	85 (18.5)	37 (8.0)	55 (12)	32 (7.0)	30 (6.5)	0.85	< 0.001
T2_a	453	61 (13.5)	47 (10.4)	31 (6.8)	31 (6.8)	30 (6.6)	16 (3.5)	0.85	< 0.001
T2_b	239	25 (10.5)	15 (6.3)	13 (5.4)	13 (5.4)	12 (5.0)	2 (0.8)	0.73	< 0.001
T3_a	228	30 (13.2)	21 (9.2)	15 (6.6)	17 (7.5)	15 (6.6)	4 (1.8)	0.72	< 0.001
T3_b	152	25 (16.4)	13 (8.6)	8 (5.3)	12 (7.9)	17 (11.2)	1 (0.7)	0.43	< 0.001

TSH thyroid stimulating hormone, ATA American Thyroid Association
^aSubgroup-specific reference values for TSH in pregnant women are defined as the lower and upper limits derived by the parametric method after normalizing the data distribution using the modified Box-Cox power transformation method: 0.34 to 3.74 mIU/L in the T1_a subgroup, 0.12 to 2.97 mIU/L in the T1_b subgroup, 0.48 to 3.00mIU/L in the T2_a subgroup, 0.68 to 3.02 mIU/L in the T2_b subgroup, 0.65 to 3.17 mIU/L in the T3_a subgroup and 0.82 to 3.20 mIU/L in the T3_b subgroup
^bGuidelines from the 2011 ATA recommendation maternal TSH between 0.1 to 2.5 mIU/L in the first trimester, 0.2 to 3.0 mIU/L in the second trimester, and 0.3 to 3.0 mIU/L in the third trimester

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