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Pediatric reference intervals for free thyroxine and free triiodothyronine
Offie P Soldin1, Megan Jang, Tiedong Guo
1Department of Oncology, Georgetown University Medical Center, Washington, DC 20007, USA. os35@georgetown.edu
Summary
This study establishes new, precise reference intervals for free thyroxine (FT4) and free triiodothyronine (FT3) in children aged 0-18 years. These findings, determined by LC/MS/MS, offer a more accurate assessment of thyroid function in pediatric populations.
Area of Science:
- Pediatric Endocrinology
- Clinical Chemistry
- Mass Spectrometry
Background:
- Accurate reference intervals for thyroid hormones free thyroxine (FT4) and free triiodothyronine (FT3) are crucial for clinical diagnosis in children.
- Existing reference intervals may lack precision, impacting the interpretation of thyroid function tests.
Purpose of the Study:
- To establish age- and sex-specific reference intervals for FT4 and FT3 in neonates, infants, and children up to 18 years of age.
- To utilize tandem mass spectrometry for precise quantification of these thyroid hormones.
Main Methods:
- Serum samples from 1426 children (FT4) and 1107 children (FT3) were analyzed.
- Isotope dilution liquid chromatography tandem mass spectrometry (LC/MS/MS) with deuterium-labeled internal standards was employed.
- Data were collected from healthy children between January 2008 and June 2008.
Main Results:
- FT4 reference intervals were similar across ages and sexes, ranging from 1.3-2.4 ng/dL (1-18 years) and 1.3-2.8 ng/dL (1-12 months).
- LC/MS/MS yielded significantly tighter FT4 intervals compared to immunoassay methods.
- FT3 intervals were consistent across ages and sexes, approximately 1.5-6.0 pg/mL (1 month-18 years).
Conclusions:
- This study provides the first pediatric reference intervals for FT4 and FT3 (birth to 18 years) using LC/MS/MS.
- LC/MS/MS offers more specific and accurate quantification of thyroid hormones.
- The LC/MS/MS method demonstrated excellent correlation with equilibrium dialysis.
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