Flores-Robles Claudia M, Roldan-Valadez Ernesto, Martínez-Cruz Nayeli, Arce-Sánchez Lidia, Priego-Zurita Ana L, Estrada-Gutierrez Guadalupe, Reyes-Muñoz Enrique
Department of Endocrinology, Instituto Nacional de Perinatología "Isidro Espinosa de los Reyes", Montes Urales 800, 11000 Mexico City, Mexico.
Directorate of Research, Hospital General de Mexico "Dr. Eduardo Liceaga", Dr. Balmis #148, 06720 Mexico City, Mexico.
Diagnostics (Basel). 2020 Jul 13;10(7):475. doi: 10.3390/diagnostics10070475.
Hypothyroxinemia of prematurity increases the rate of false-positive results in total thyroxine (tT4)-based screening programs for congenital hypothyroidism. The use of specific cutoff values for preterm infants has been proposed, but data on tT4 reference ranges in this population are limited. The primary aim was to establish reference percentiles for tT4 in dried blood spots among Mexican preterm infants. Secondary aims included a comparison of the change of tT4 concentrations over time according to gestational age and to discuss its impact on tT4-based screening programs. This was a retrospective cohort study; 1561 preterm infants were included. Percentile 10th for tT4 concentration at 24-27, 28-30, 31-34, and 35-36 weeks of gestational age, measured in the first week of life was: 47.6, 56.6, 82.3, and 117.1 nmol/L, respectively. tT4 concentrations were compared in three different time points: first week of life, 2-3 weeks of life, and term-corrected gestational age (38 weeks of gestation), progressively increased in infants below 30 weeks, remained stable in infants from 31 to 34 weeks, and decreased in late preterm newborns (35-36 weeks). This study suggests that preterm infants may require the use of lower tT4 cutoff values in newborn screening.
早产儿甲状腺素水平低下会增加先天性甲状腺功能减退症基于总甲状腺素（tT4）筛查项目的假阳性率。有人提议为早产儿设定特定的临界值，但该人群tT4参考范围的数据有限。主要目的是确定墨西哥早产儿干血斑中tT4的参考百分位数。次要目的包括根据胎龄比较tT4浓度随时间的变化，并讨论其对基于tT4的筛查项目的影响。这是一项回顾性队列研究；纳入了1561名早产儿。在出生后第一周测量的24 - 27周、28 - 30周、31 - 34周和35 - 36周胎龄时tT4浓度的第10百分位数分别为：47.6、56.6、82.3和117.1 nmol/L。在三个不同时间点比较了tT4浓度：出生后第一周、出生后2 - 3周和足月校正胎龄（妊娠38周），30周以下的婴儿tT4浓度逐渐升高，31至34周的婴儿保持稳定，晚期早产儿（35 - 36周）tT4浓度下降。这项研究表明，早产儿在新生儿筛查中可能需要使用较低的tT4临界值。
