Yang Lili, Zhang Yu, Yang Jianbin, Huang Xinwen
Department of Genetics and Metabolism, Children's Hospital, Zhejiang University School of Medicine, Hangzhou, China.
Ann Clin Biochem. 2018 Jan;55(1):92-99. doi: 10.1177/0004563216688038. Epub 2017 Mar 9.
Background Birth weight influences profiles of dried blood amino-acids and acylcarnitines in newborn screening. This study aimed to define a more appropriate cut-off value to reduce the false positive rate and the number of recalled patients in newborn screening. Methods All babies who underwent newborn screening in our center were included; they were divided into groups by birth weight: 2500-3999 g (comparator group), <1000 g (group 1), 1000-1499 g (group 2), 1500-2499 g (group 3), and >4000 g (group 4). The 0.5th and 99.5th percentiles were used as the cut-off values. Comparisons were done on amino acid and acylcarnitines concentrations between the groups. False positive rate, positive predictive value, corrected false positive rate by birth weights were determined. Results Data on a total of 578,287 newborn infants were included in the analysis. The total false positive rate was 0.75%, and positive predictive value 2.89%. The false positive rate was 0.69%, 0.54% and 5.31% in infants with normal birth weight, birth weight of >4000 (group 4) and low birth weight of < 2500 g (groups 1, 2 and 3), respectively. Low-birth weight infants had much higher phenylalanine, tyrosine, methionine, arginine, propionylcarnitine, isovalerylcarnitine and octadecanoylcarnitine concentrations. Free carnitines and palmitoylcarnitine concentrations were lower. After adjusting for birth weight, false positive rate of all indices decreased to 0.53%, and positive predictive value increased to 4.31%. Conclusions Amino acid and carnitine concentrations in low-birth weight newborn infants may differ from the normal term newborn infants. The cut-off values of individual metabolites should be adjusted based on birth weight, to reduce false positive rate and increase positive predictive value.
背景 出生体重会影响新生儿筛查中干血氨基酸和酰基肉碱的谱图。本研究旨在确定一个更合适的临界值，以降低新生儿筛查中的假阳性率和召回患者的数量。方法 纳入在本中心接受新生儿筛查的所有婴儿；按出生体重将他们分为几组：2500 - 3999克（对照组）、<1000克（第1组）、1000 - 1499克（第2组）、1500 - 2499克（第3组）和>4000克（第4组）。将第0.5百分位数和第99.5百分位数用作临界值。对各组之间的氨基酸和酰基肉碱浓度进行比较。确定假阳性率、阳性预测值、按出生体重校正的假阳性率。结果 分析共纳入578287例新生儿的数据。总假阳性率为0.75%，阳性预测值为2.89%。出生体重正常的婴儿、出生体重>4000克（第4组）和出生体重<2500克的低体重婴儿（第1、2和3组）的假阳性率分别为0.69%、0.54%和5.31%。低体重婴儿的苯丙氨酸、酪氨酸、蛋氨酸、精氨酸、丙酰肉碱、异戊酰肉碱和十八烷酰肉碱浓度要高得多。游离肉碱和棕榈酰肉碱浓度较低。在调整出生体重后，所有指标的假阳性率降至0.53%，阳性预测值升至4.31%。结论 低体重新生儿的氨基酸和肉碱浓度可能与足月儿不同。应根据出生体重调整个体代谢物的临界值，以降低假阳性率并提高阳性预测值。
