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Effects of Sample Handling and Analytical Procedures on Thyroid Hormone Concentrations in Pregnant Women’s Plasma

Villanger, Gro Dehli; Learner, Emily; Longnecker, Matthew P.; Ask, Helga; Aase, Heidi; Zoeller, R. Thomas; Knudsen, Gun P.; Reichborn-Kjennerud, Ted; Zeiner, Pål; Engel, Stephanie M.

doi: 10.1097/EDE.0000000000000606

Background: Maternal thyroid function is a critical mediator of fetal brain development. Pregnancy-related physiologic changes and handling conditions of blood samples may influence thyroid hormone biomarkers. We investigated the reliability of thyroid hormone biomarkers in plasma of pregnant women under various handling conditions.

Methods: We enrolled 17 pregnant women; collected serum and plasma were immediately frozen. Additional plasma aliquots were subjected to different handling conditions before the analysis of thyroid biomarkers: storage at room temperature for 24 or 48 hours before freezing and an extra freeze–thaw cycle. We estimated free thyroid hormone indices in plasma based on T3 uptake.

Results: High correlations between plasma and serum (>0.94) and intraclass correlation coefficients for plasma handling conditions (0.96 to 1.00) indicated excellent reliability for all thyroid hormone biomarkers.

Conclusion: Delayed freezing and freeze–thaw cycles did not affect reliability of biomarkers of thyroid function in plasma during pregnancy. See video abstract at,

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From the aNorwegian Institute of Public Health, Mental and Physical Health, Oslo, Norway; bDepartment of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC; cNational Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC; dBiology Department, University of Massachusetts-Amherst, Amherst, MA; and eDivision of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway.

Submitted 13 October 2015; accepted 27 November 2016.

This study was supported in part by R01ES021777, the Intramural Research Program, The National Institutes of Environmental Health Sciences (NIEHS), the National Institutes of Health (NIH), and The Norwegian Institute of Public Health.

The authors report no conflicts of interest.

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Correspondence: Gro Dehli Villanger, Norwegian Institute of Public Health, P.O. Box 4404, N-0403 Oslo, Norway. E-mail:

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