Department of Epidemiology, Tulane School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana, USA
Department of Epidemiology, Tulane School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana, USA.
Arch Dis Child. 2020 May;105(5):428-432. doi: 10.1136/archdischild-2019-317678. Epub 2019 Dec 13.
The Zika virus outbreak has drawn attention to microcephaly, whose definition is based on head circumference measuring below a percentile or number of SDs below the mean. The objective of this analysis was to assess how differences in measurement precision might affect prevalence and trends of microcephaly.
Data from all births in Uruguay during 2010-2015 were obtained from the Perinatal Information System. The prevalence of births with microcephaly was calculated based on head circumference measurement at birth applying the INTERGROWTH-21 standards for sex and gestational age, and compared by method of ascertaining gestational age.
Rounding and digit preference was observed: 74% of head circumference measurements were reported as a whole centimetre value. The prevalence of births varied substantially by the criterion used to define microcephaly (<3 SD, <2 SD, <3rd percentile for gestational age) and could be halved or doubled based on adding or subtracting a half-centimetre from all reported head circumference measurements. If 4 days were added to gestational age calculations, rather than using completed gestational weeks (without days) for gestational age reporting, the prevalence was 1.7-2 times higher.
Rounding in measurement of head circumference and reporting preferences of gestational age may have contributed to a lower prevalence of microcephaly than expected in this population. Differences in head circumference measurement protocols and gestational age dating have the potential to affect the prevalence of babies reported with microcephaly, and this limitation should be acknowledged when interpreting head circumference data collected for surveillance.
寨卡病毒的爆发引起了人们对小头症的关注，其定义基于头围低于百分位数或平均值的标准差数。本分析的目的是评估测量精度的差异如何影响小头症的流行率和趋势。
从乌拉圭 2010 年至 2015 年期间所有出生的围产儿信息系统中获得数据。根据 INTERGROWTH-21 标准的性别和胎龄，在出生时对头围进行测量，计算小头症出生的流行率，并按确定胎龄的方法进行比较。
观察到头围测量值存在四舍五入和数字偏好：74%的头围测量值以整厘米值报告。小头症的定义标准（<3 个标准差、<2 个标准差、<胎龄的第 3 个百分位数）不同，小头症出生的流行率差异很大，根据在所有报告的头围测量值上增加或减少半厘米，流行率可以减半或翻倍。如果将 4 天添加到胎龄计算中，而不是使用完整的孕周（无天数）报告胎龄，流行率将增加 1.7-2 倍。
头围测量的四舍五入和胎龄报告偏好可能导致该人群的小头症流行率低于预期。头围测量方案和胎龄日期的差异有可能影响报告的小头症婴儿的流行率，在解释为监测收集的头围数据时，应承认这一局限性。
