Document Detail

Assessment of thyroid function during pregnancy: first-trimester (weeks 9-13) reference intervals derived from Western Australian women.
MedLine Citation:
PMID:  18759718     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: To establish first-trimester-specific reference intervals for thyroid function tests in pregnant Australian women. DESIGN, SETTING AND PARTICIPANTS: Serum samples were collected from 2159 pregnant women (9-13 weeks' gestation) attending a private pathology practice for first-trimester screening during October and November 2006. Levels of serum thyrotropin (TSH), free thyroxine (fT4), free triiodothyronine (fT3), thyroid peroxidase antibodies (TPOAb), and thyroglobulin antibodies (TgAb) were measured by chemiluminescent immunoassay (Abbott ARCHITECT analyser). MAIN OUTCOME MEASURES: Reference intervals based on 2.5th and 97.5th percentiles for TSH, fT4 and fT3, after exclusion of 338 women with positive TPOAb or TgAb tests; comparison with reference intervals for non-pregnant women (TSH, 0.40-4.0 mU/L; fT4, 9-19 pmol/L; fT3, 3.0-5.5 pmol/L). RESULTS: Derived reference intervals for thyroid function tests during the first trimester of pregnancy were: TSH, 0.02-2.15 mU/L; fT4, 10.4-17.8 pmol/L; and fT3, 3.3-5.7 pmol/L. If the non-pregnant TSH reference range was applied to the study participants, 344 women (16.0%) whose serum TSH concentration was within the first-trimester-specific reference range would be misclassified as having subclinical hyperthyroidism, and 98 women (4.5%) with a TSH concentration above the first-trimester-specific upper reference limit would not be identified. CONCLUSIONS: The reference interval for TSH during the first trimester of pregnancy differs substantially from that for non-pregnant women, and applying the general laboratory reference range to pregnant women results in misclassification of thyroid status for 20.5% of women. Australian pathology laboratories should adopt pregnancy-specific reference intervals for thyroid function tests.
Rhonda M Gilbert; Narelle C Hadlow; John P Walsh; Stephen J Fletcher; Suzanne J Brown; Bronwyn G Stuckey; Ee Mun Lim
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The Medical journal of Australia     Volume:  189     ISSN:  0025-729X     ISO Abbreviation:  Med. J. Aust.     Publication Date:  2008 Sep 
Date Detail:
Created Date:  2008-09-01     Completed Date:  2008-10-22     Revised Date:  2009-04-09    
Medline Journal Info:
Nlm Unique ID:  0400714     Medline TA:  Med J Aust     Country:  Australia    
Other Details:
Languages:  eng     Pagination:  250-3     Citation Subset:  IM    
Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, and School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia.
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MeSH Terms
Chorionic Gonadotropin, beta Subunit, Human / blood
Pregnancy / blood*
Pregnancy Trimester, First
Reference Values
Thyroid Function Tests
Thyroid Gland / physiology*
Thyrotropin / blood*
Thyroxine / blood*
Triiodothyronine / blood*
Western Australia
Reg. No./Substance:
0/Chorionic Gonadotropin, beta Subunit, Human; 6893-02-3/Triiodothyronine; 7488-70-2/Thyroxine; 9002-71-5/Thyrotropin
Comment In:
Med J Aust. 2009 Feb 16;190(4):219-20   [PMID:  19220192 ]

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