Rounding of birth weights in a neonatal intensive care unit over 20 years: an analysis of a large cohort study

Abstract

ObjectiveTo determine the frequency of birth weight digit preference for infants admitted to a large neonatal intensive care unit (NICU), the scale of rounding and its dependence on birth weight, and time and the impact on prescribing accuracy.DesignA consecutive cohort of birth weights extracted retrospectively from a single clinical database.Setting and participantsBirth weights from 9170 inborn infants recorded on an electronic prescribing database admitted to NICU over 20 years.Statistical approachData are presented for the frequency of each of the possible pairs of final digits. A statistical model of digit preference assuming rounding is used to quantify the proportions rounding to specific accuracy levels. These proportions are compared between those <1000 g and those above and over the 20-year time period.ResultsFrom a population of 9170 infants admitted over 20 years, there was a highly statistically significant digit bias with an increased prevalence of multiples of 100 (p<0.0001), 50 (p=0.007), 20 (p<0.0001), 10 (p<0.0001), 5 (p<0.0001) and 2 (p=0.0005). There was clear evidence of a reduced 100 g digit bias for infants 500 and 1000 g (0%) compared with those between 1000 and 4500 g (3.7%). The maximum birth weight error due to digit bias for all infants was 5%. There was clear evidence of an improvement in accuracy over 20 years.ConclusionsDigit bias in birth weights over 20 years in a tertiary NICU is highly significant at the 100, 50, 20, 10, 5 and 2-digit levels. There has been a substantial improvement in the accuracy of birth weight measurements over 20 years. The likely maximum error due to birth weight digit bias is 5% and is within an acceptable tolerance for drug dosing even at very low birth weights.

Antibiotic prescribing in neonatal sepsis: an Australian nationwide survey

“…In one study of more than 9000 neonates over a 20-year period, weight error due to digit bias (whereby round numbers are favoured) improved over 20 years but was still evident in neonates between 1000 and 4500 g at ≤5%. 31 Relative to body size, this phenomenon accounts for additional variation not seen in the adult population, where standardised doses are used, and the implications of this variation for research and practice improvement remain insufficiently understood.…”

Examining the link between women's exposure to stressful life events prior to conception and infant and toddler health: the role of birth weight

“…The number of individuals who endorsed specific PSLEs was small so we were unable to examine the independent effects of each type of event. The null finding of an indirect effect of PSLEs on child health through LBW could be explained by several mechanisms, including misclassification of infant birthweight[33, 34] or undetected dose-response effects. Alternatively, this finding may indicate that the effects of stressors on child health operate only via extreme effects on fetal growth.…”

Modelling Trends in Digit Preference Patterns

“…Accurate measurements of birth weight are particularly important in neonatal intensive care when drug prescription is weight based, and misreporting of weight can be especially detrimental for very small babies. Emmerson and Roberts () reported a study in which birth weights in a neonatal intensive care unit were recorded over 20 years, and birth weights of 9170 newborns were analysed. Weights were obtained by digital scales with 1‐g resolution; however, as Fig.…”

“…In this paper we present a model for digit preference and the trend in the preference pattern over a second dimension, which in most cases will be calendar time. We use the same data as Emmerson and Roberts () to estimate the trend in improvement against digit preference in birth weights as well as the preference pattern itself.…”

“… Proportion of the last two end digits in the birth weight data from Emmerson and Roberts () for the earlier (, June 1994–May 2004) and later (, June 2004–May 2013) observation period…”