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Method specific second-trimester reference intervals for thyroid-stimulating hormone and free thyroxine.
Rechelle Silvio1, Karly J Swapp, Sonia L La'ulu
1Department of Clinical Laboratory Sciences, Weber State University, Ogden, UT, USA.
Clinical Biochemistry
|January 7, 2009
Summary
Establishing second trimester reference intervals for thyroid-stimulating hormone (TSH) and free thyroxine (FT4) is crucial. New method-specific intervals are needed, as current assays show variability.
Area of Science:
- Endocrinology
- Clinical Chemistry
- Reproductive Medicine
Background:
- Thyroid hormones, including TSH and FT4, play a vital role in pregnancy.
- Accurate reference intervals are essential for diagnosing thyroid dysfunction during the second trimester.
- Assay methodology can influence thyroid hormone measurements.
Purpose of the Study:
- To establish reference intervals for TSH and FT4 in the second trimester of pregnancy.
- To evaluate the performance of the Elecsys E170 assay for TSH and FT4 in this population.
Main Methods:
- Analysis of samples from 3102 subjects.
- Exclusion of samples with thyroid peroxidase (TPO) and thyroglobulin (Tg) antibodies.
- Determination of reference intervals using antibody-negative samples on the Elecsys E170 platform.
Main Results:
- Second trimester reference intervals for TSH: 0.18–4.07 mIU/L.
- Second trimester reference intervals for FT4: 9.5–15.8 pmol/L.
- The Elecsys E170 TSH assay demonstrated a positive bias compared to the ARCHITECT i2000(SR) assay.
Conclusions:
- Method-specific reference intervals for TSH and FT4 are necessary for accurate interpretation in the second trimester.
- Assay differences highlight the importance of using appropriate reference ranges for specific laboratory platforms.
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