Developing a national birth cohort for child health research using a hospital admissions database in England: The impact of changes to data collection practices

Abstract

Background National birth cohorts derived from administrative health databases constitute unique resources for child health research due to whole country coverage, ongoing follow-up and linkage to other data sources. In England, a national birth cohort can be developed using Hospital Episode Statistics (HES), an administrative database covering details of all publicly funded hospital activity, including 97% of births, with longitudinal follow-up via linkage to hospital and mortality records. We present methods for developing a national birth cohort using HES and assess the impact of changes to data collection over time on coverage and completeness of linked follow-up records for children. Methods We developed a national cohort of singleton live births in 1998–2015, with information on key risk factors at birth (birth weight, gestational age, maternal age, ethnicity, area-level deprivation). We identified three changes to data collection, which could affect linkage of births to follow-up records: (1) the introduction of the “NHS Numbers for Babies (NN4B)”, an on-line system which enabled maternity staff to request a unique healthcare patient identifier (NHS number) immediately at birth rather than at civil registration, in Q4 2002; (2) the introduction of additional data quality checks at civil registration in Q3 2009; and (3) correcting a postcode extraction error for births by the data provider in Q2 2013. We evaluated the impact of these changes on trends in two outcomes in infancy: hospital readmissions after birth (using interrupted time series analyses) and mortality rates (compared to published national statistics). Results The cohort covered 10,653,998 babies, accounting for 96% of singleton live births in England in 1998–2015. Overall, 2,077,929 infants (19.5%) had at least one hospital readmission after birth. Readmission rates declined by 0.2% percentage points per annual quarter in Q1 1998 to Q3 2002, shifted up by 6.1% percentage points (compared to the expected value based on the trend before Q4 2002) to 17.7% in Q4 2002 when NN4B was introduced, and increased by 0.1% percentage points per annual quarter thereafter. Infant mortality rates were under-reported by 16% for births in 1998–2002 and similar to published national mortality statistics for births in 2003–2015. The trends in infant readmission were not affected by changes to data collection practices in Q3 2009 and Q2 2013, but the proportion of unlinked mortality records in HES and in ONS further declined after 2009. Discussion HES can be used to develop a national birth cohort for child health research with follow-up via linkage to hospital and mortality records for children born from 2003 onwards. Re-linking births before 2003 to their follow-up records would maximise potential benefits of this rich resource, enabling studies of outcomes in adolescents with over 20 years of follow-up.

Access to palivizumab among children at high risk of respiratory syncytial virus complications in English hospitals

“…However, birth cohorts derived from HES data have been extensively validated and widely used for research of birth outcomes. [28][29][30][31] Further, we demonstrated that the distribution of recorded gestational age among births identified in HTI was representative of births in England, and the distribution of risk factors among eligible infants with and without any missing data were comparable. Linkage of HES to NHS Birth Notification database (maintained by NHS Digital) could provide complete information on key birth characteristics for all births.…”

“…Missing data rates were comparable to these reported in wholecountry birth cohorts derived from HES. 28,29 Completeness and accuracy of gestational age is known to vary between hospitals (as submission of these variables to HES is not mandatory), with some hospitals reporting no recorded data, and some reporting invalid data which were removed when preparing the cohort. 29 We could not use multiple imputation to take missing data into account in our models, since multiple imputation requires all analyses to be run on the same sample size.…”

Birth prevalence of anorectal malformations in England and 5-year survival: a national birth cohort study

“…HES contains details of all admissions to National Health Service (NHS)-funded hospitals and captures 97% of births in England 15. Maternal and infant birth admissions contain information about maternal and infant characteristics, while subsequent infant hospital admissions enable longitudinal follow-up 15 16. Diagnoses and procedures in HES are recorded using the International Classification of Diseases 10th revision (ICD-10) and the Classification of Surgical Operations and Procedures, respectively.…”

Scaling up research on family justice using large-scale administrative data: an invitation to the socio-legal community

“…By linking data we gain a less fragmented view of individual interaction with, or pathways through services and the courts (Jay et al 2017). In addition, there is a wealth of excellent literature on approaches to data linkage (Harron et al 2017, Zylbersztejn et al 2020). In the discipline of health in particular, there are multiple examples of robust studies that have linked data across organisational sources to build holistic analyses of patients' engagement with health services and their outcomes (Harron et al 2020).…”