Ann Lab Med.  2015 Mar;35(2):198-204. 10.3343/alm.2015.35.2.198.

Establishment of Trimester-Specific Reference Intervals for Thyroid Hormones in Korean Pregnant Women

• Moon HW
• Chung HJ
• Park CM
• Hur M
• Yun YM

• KMID: 2363179
• DOI: http://doi.org/10.3343/alm.2015.35.2.198

Abstract

BACKGROUND
Establishment of trimester- and assay-specific reference intervals for every population is recommended. The aim of this study was to establish a trimester- and assay-specific reference interval for thyroid-stimulating hormone (TSH) and free thyroxine (FT4) in Korean pregnant women.
METHODS
From April 2012 to December 2012, 531 pregnant women receiving prenatal care and 238 age-matched, non-pregnant women were enrolled in this study. After excluding patients with pregnancy-associated complications or thyroid-specific autoantibody, 465 pregnant and 206 non-pregnant women were included. Non-parametric analysis (2.5-97.5th percentile) was performed to determine the reference interval. Levels of TSH and FT4 were determined by electrochemiluminescence immunoassay (Elecsys thyroid tests, Roche Diagnostics, Germany).
RESULTS
The TSH reference intervals were 0.01-4.10, 0.01-4.26, and 0.15-4.57 mIU/L for the first, second, and third trimester, respectively. From the first trimester to the third trimester, the median TSH levels showed a significantly increasing trend (P<0.0001). The FT4 reference intervals were 0.83-1.65, 0.71-1.22, and 0.65-1.13 ng/dL for the first, second, and third trimester, respectively, showing a significantly decreasing trend (P<0.0001).
CONCLUSIONS
Establishing trimester-specific reference intervals in pregnant women is essential for accurate assessment of thyroid function. Our population-specific and method-specific reference intervals will be useful for screening Korean pregnant women for thyroid disease.

Keyword

TSH; FT4; Reference interval; Korean; Pregnancy; Trimester

MeSH Terms

Adult
Asian Continental Ancestry Group
Case-Control Studies
Female
Humans
*Immunoassay/standards
Luminescent Measurements
Pregnancy
Pregnancy Trimesters
Prenatal Care
Reference Values
Republic of Korea
Thyroid Hormones/*analysis/standards
Thyroxine/*analysis/standards
Thyroid Hormones
Thyroxine

Figure

• 

  Fig. 1 Trends of TSH (A) and FT4 (B) levels during each trimester of pregnancy and non-pregnancy. A significantly increasing trend of TSH level from the first to the third trimester was observed (P<0.001), and FT4 level showed a significantly decreasing trend with an increase in gestational age (P<0.001), which was lowest in the third trimester. The central box represents values from the lower to the upper quartile. The middle line represents the median and the bars represent the 2.5th and 97.5th percentile.Abbreviations: TSH, thyroid stimulating hormone; FT4, free thyroxine.

• 

  Fig. 2 Bland-Altman plots showing differences between Elecsys and ADVIA Centaur in TSH (A) and FT4 (B) measurements using 55 specimens of pregnant women. Thick solid lines represent the mean bias (means of paired differences). Dashed lines represent 95% limits of agreement (bias±1.96 SD).Abbreviations: TSH, thyroid stimulating hormone; FT4, free thyroxine.

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