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Incidence of Low Free T4 Values in Premature Infants as Determined by Direct Equilibrium Dialysis

Journal of Perinatology volume 24, pages 640–644 (2004)Cite this article

Abstract

BACKGROUND: The incidence of transient reductions in serum free T4 (FT4) in premature infants may be overestimated because certain FT4 analytical methods underestimate FT4 concentrations. Transient reductions of FT4 measurements have been reported in the majority of premature newborn infants. Direct equilibrium dialysis (DED) does not underestimate FT4 concentrations and is the best available technique to measure serum FT4 in the premature infant.

OBJECTIVE: To evaluate the incidence of low FT4 concentrations in premature infants using DED to measure FT4.

DESIGN/METHOD: We measured FT4 by DED in infants with birth weight <1500 g. Infants were excluded if the following conditions were present: congenital anomalies or maternal thyroid disorders. Free T4 was measured at 14 days of life. Low FT4 was defined using a statistical definition of FT4 measurements <10.3 pmol/l (0.8 ng/dl).

RESULTS: Free T4 was measured by DED in 114 infants. Low FT4 levels were seen in nine infants (7.9%).

CONCLUSION: The incidence of low FT4 was much lower than previously reported when FT4 was measured using DED indicating that methodological issues are involved in the variability among estimates of the frequency of transient reduction in FT4.

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Authors and Affiliations

  1. Department of Pediatrics, Coleman Pavilion Room 11121C, Loma Linda University School of Medicine, 11175 Campus Street, Coleman Pavilion, Suite 11121, Loma Linda, 92354, CA, USA

    Christopher W Rabin DO, Andrew O Hopper MD, Leela Job MD, Ricardo L Peverini MD, Susan J Clark MD, Douglas D Deming MD, Jerald C Nelson MD & Nidia R Vyhmeister MD

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Rabin, C., Hopper, A., Job, L. et al. Incidence of Low Free T4 Values in Premature Infants as Determined by Direct Equilibrium Dialysis. J Perinatol 24, 640–644 (2004). https://doi.org/10.1038/sj.jp.7211109

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