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 4 Comparison between ATA and trimester-specific reference intervals

Trimester	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
Trimester	No. of subjects	Trimester-specific^a	ATA guidelines^b	Trimester specific^a	ATA guidelines^b	Trimester-specific^a	ATA guidelines^b	Kappa value	P value
First	705	116 (16.5)	134 (19.0)	60 (8.5)	102 (14.5)	56 (7.9)	32 (4.5)	0.69	< 0.001
Second	692	94 (13.6)	62 (9.0)	43 (6.2)	44 (6.4)	51 (7.4)	18 (2.6)	0.76	< 0.001
Third	380	44 (11.6)	34 (8.9)	22 (5.8)	29 (7.6)	22 (5.8)	5 (1.3)	0.66	< 0.001

TSH Thyroid stimulating hormone, ATA American Thyroid Association
^aTrimester-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: 0.23 to 3.09 mIU/L in the first trimester, 0.54 to 3.01 mIU/L in the second trimester, 0.66 to 3.23 mIU/L in the third trimester. ^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

ISSN: 1471-2393