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

BACKGROUND: The incidence of transient reductions in serum free T 4 (FT 4 ) in premature infants may be overestimated because certain FT 4 analytical methods underestimate FT 4 concentrations. Transient reductions of FT 4 measurements have been reported in the majority of premature newborn infants. Direct equilibrium dialysis (DED) does not underestimate FT 4 concentrations and is the best available technique to measure serum FT 4 in the premature infant. OBJECTIVE: To evaluate the incidence of low FT 4 concentrations in premature infants using DED to measure FT 4 . DESIGN/METHOD: We measured FT 4 by DED in infants with birth weight