Evaluation of Thyroid Function in Pregnant Women Using Automated Immunoassays
Autor: | Robert D Nerenz, K. Aaron Geno, Mark A. Cervinski, Matthew S Reed |
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Rok vydání: | 2020 |
Předmět: |
0301 basic medicine
medicine.medical_specialty Clinical Biochemistry Thyroid Gland Thyrotropin 030209 endocrinology & metabolism Context (language use) Thyroid Function Tests 03 medical and health sciences 0302 clinical medicine Pregnancy Reference Values Medicine Humans Euthyroid Immunoassay business.industry Obstetrics Biochemistry (medical) Thyroid Gestational age medicine.disease Anti-thyroid autoantibodies Thyroxine 030104 developmental biology medicine.anatomical_structure Female Pregnant Women Thyroid function business hormones hormone substitutes and hormone antagonists Hormone |
Zdroj: | Clinical chemistry. 67(5) |
ISSN: | 1530-8561 |
Popis: | Introduction Automated free thyroxine (FT4) immunoassays are widely available, but professional guidelines discourage their use in pregnant women due to theoretical under-recoveries attributed to increased thyroid hormone binding capacity and instead advocate the use of total T4 (TT4) or free thyroxine index (FTI). The impact of this recommendation on the classification of thyroid status in apparently euthyroid pregnant patients was evaluated. Methods After excluding specimens with thyroid autoantibody concentrations above reference limits, thyroid-stimulating hormone (TSH), FT4, TT4, and T-uptake were measured on the Roche Cobas® platform in remnant clinical specimens from at least 147 nonpregnant women of childbearing age and pregnant women at each trimester. Split-sample comparisons of FT4 as measured by the Cobas and equilibrium dialysis were performed. Results FT4 decreased with advancing gestational age by both immunoassay and equilibrium dialysis. TSH declined during the first trimester, remained constant in the second, and increased throughout the third, peaking just before delivery. Interpretation of TT4 concentrations using 1.5-times the nonpregnant reference interval classified 13.6% of first trimester specimens below the lower reference limit despite TSH concentrations within trimester-specific reference intervals. Five FTI results from 480 pregnant individuals (about 1.0%) fell outside the manufacturer’s reference interval. Conclusions Indirect FT4 immunoassay results interpreted in the context of trimester-specific reference intervals provide a practical and viable alternative to TT4 or FTI. Declining FT4 and increasing TSH concentrations near term suggest that declining FT4 is not an analytical artifact but represents a true physiological change in preparation for labor and delivery. |
Databáze: | OpenAIRE |
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