Does Unprecedented ICU Capacity Strain, As Experienced During the COVID-19 Pandemic, Impact Patient Outcome?

OBJECTIVES: To determine whether patients admitted to an ICU during times of unprecedented ICU capacity strain, during the COVID-19 pandemic in the United Kingdom, experienced a higher risk of death. DESIGN: Multicenter, observational cohort study using routine clinical audit data. SETTING: Adult general ICUs participating the Intensive Care National Audit & Research Centre Case Mix Programme in England, Wales, and Northern Ireland. PATIENTS: One-hundred thirty-thousand six-hundred eighty-nine patients admitted to 210 adult general ICUs in 207 hospitals. INTERVENTIONS: Multilevel, mixed effects, logistic regression models were used to examine the relationship between levels of ICU capacity strain on the day of admission (typical low, typical, typical high, pandemic high, and pandemic extreme) and risk-adjusted hospital mortality. MEASUREMENTS AND MAIN RESULTS: In adjusted analyses, compared with patients admitted during periods of typical ICU capacity strain, we found that COVID-19 patients admitted during periods of pandemic high or pandemic extreme ICU capacity strain during the first wave had no difference in hospital mortality, whereas those admitted during the pandemic high or pandemic extreme ICU capacity strain in the second wave had a 17% (odds ratio [OR], 1.17; 95% CI, 1.05-1.30) and 15% (OR, 1.15; 95% CI, 1.00-1.31) higher odds of hospital mortality, respectively. For non-COVID-19 patients, there was little difference in trend between waves, with those admitted during periods of pandemic high and pandemic extreme ICU capacity strain having 16% (OR, 1.16; 95% CI, 1.08-1.25) and 30% (OR, 1.30; 95% CI, 1.14-1.48) higher overall odds of acute hospital mortality, respectively. CONCLUSIONS: For patients admitted to ICU during the pandemic, unprecedented levels of ICU capacity strain were significantly associated with higher acute hospital mortality, after accounting for differences in baseline characteristics. Further study into possible differences in the provision of care and outcome for COVID-19 and non-COVID-19 patients is needed.

Trends in Intensive Care for Patients with COVID-19 in England, Wales, and Northern Ireland.

Rationale: By describing trends in intensive care for patients with coronavirus disease (COVID-19) we aim to support clinical learning, service planning, and hypothesis generation.Objectives: To describe variation in ICU admission rates over time and by geography during the first wave of the epidemic in England, Wales, and Northern Ireland; to describe trends in patient characteristics on admission to ICU, first-24-hours physiology in ICU, processes of care in ICU and patient outcomes; and to explore deviations in trends during the peak period.Methods: A cohort of 10,741 patients with COVID-19 in the Case Mix Program national clinical audit from February 1 to July 31, 2020, was used. Analyses were stratified by time period (prepeak, peak, and postpeak periods) and geographical region. Logistic regression was used to estimate adjusted differences in 28-day in-hospital mortality between periods.Measurements and Main Results: Admissions to ICUs peaked almost simultaneously across regions but varied 4.6-fold in magnitude. Compared with patients admitted in the prepeak period, patients admitted in the postpeak period were slightly younger but with higher degrees of dependency and comorbidity on admission to ICUs and more deranged first-24-hours physiology. Despite this, receipt of invasive ventilation and renal replacement therapy decreased, and adjusted 28-day in-hospital mortality was reduced by 11.8% (95% confidence interval, 8.7%-15.0%). Many variables exhibited u-shaped or n-shaped curves during the peak.Conclusions: The population of patients with COVID-19 admitted to ICUs, and the processes of care in ICUs, changed over the first wave of the epidemic. After adjustment for important risk factors, there was a substantial improvement in patient outcomes.

Assessing data linkage quality in cohort studies.

Background: Linkage of administrative data sources provides an efficient means of collecting detailed data on how individuals interact with cross-sectoral services, society, and the environment. These data can be used to supplement conventional cohort studies, or to create population-level electronic cohorts generated solely from administrative data. However, errors occurring during linkage (false matches/missed matches) can lead to bias in results from linked data.Aim: This paper provides guidance on evaluating linkage quality in cohort studies.Methods: We provide an overview of methods for linkage, describe mechanisms by which linkage error can introduce bias, and draw on real-world examples to demonstrate methods for evaluating linkage quality.Results: Methods for evaluating linkage quality described in this paper provide guidance on (i) estimating linkage error rates, (ii) understanding the mechanisms by which linkage error might bias results, and (iii) information that should be shared between data providers, linkers and users, so that approaches to handling linkage error in analysis can be implemented.Conclusion: Linked administrative data can enhance conventional cohorts and offers the ability to answer questions that require large sample sizes or hard-to-reach populations. Care needs to be taken to evaluate linkage quality in order to provide robust results.

Evaluating the clinical and cost-effectiveness of a conservative approach to oxygen therapy for invasively ventilated adults in intensive care: Protocol for the UK-ROX trial.

Background: In the United Kingdom, around 184,000 adults are admitted to an intensive care unit (ICU) each year with over 30% receiving mechanical ventilation. Oxygen is the commonest therapeutic intervention provided to these patients but it is unclear how much oxygen should be administered for the best clinical outcomes. Methods: The UK-ROX trial will evaluate the clinical and cost-effectiveness of conservative oxygen therapy (the minimum oxygen concentration required to maintain an oxygen saturation of 90% ± 2%) versus usual oxygen therapy in critically ill adults receiving supplemental oxygen when invasively mechanically ventilated in ICUs in England, Wales and Northern Ireland. The trial will recruit 16,500 patients from approximately 100 UK adult ICUs. Using a deferred consent model, enrolled participants will be randomly allocated (1:1) to conservative or usual oxygen therapy until ICU discharge or 90 days after randomisation. Objectives: The primary clinical outcome is all cause mortality at 90 days following randomisation. Discussion: The UK-ROX trial has received ethical approval from the South Central - Oxford C Research Ethics Committee (Reference: 20/SC/0423) and the Confidentiality Advisory Group (Reference: 22/CAG/0154). The trial commenced in May 2021 and, at the time of publication, 95 sites had opened to recruitment.

Risk of death following COVID-19 vaccination or positive SARS-CoV-2 test in young people in England.

Several studies have reported associations between COVID-19 vaccination and risk of cardiac diseases, especially in young people; the impact on mortality, however, remains unclear. We use national, linked electronic health data in England to assess the impact of COVID-19 vaccination and positive SARS-CoV-2 tests on the risk of cardiac and all-cause mortality in young people (12 to 29 years) using a self-controlled case series design. Here, we show there is no significant increase in cardiac or all-cause mortality in the 12 weeks following COVID-19 vaccination compared to more than 12 weeks after any dose. However, we find an increase in cardiac death in women after a first dose of non mRNA vaccines. A positive SARS-CoV-2 test is associated with increased cardiac and all-cause mortality among people vaccinated or unvaccinated at time of testing.

The association between time of in hospital cardiac arrest and mortality; a retrospective analysis of two UK databases.

AIMS: The incidence of in hospital cardiac arrest (IHCA) varies throughout the day. This study aimed to report the variation in incidence of IHCA, presenting rhythm and outcome based on the hour in which IHCA occurred. METHODS: We conducted a retrospective analysis of the National Cardiac Arrest Audit (NCAA) including patients who suffered an IHCA from 1st April 2011 to 31st December 2019. We then linked the NCAA and intensive care Case Mix Programme databases to explore the effect of time of IHCA on hospital survival in the subgroup of patients admitted to intensive care following IHCA. RESULTS: We identified 115,690 eligible patients in the NCAA database. Pulseless electrical activity was the commonest presenting rhythm (54.8%). 66,885 patients died in the immediate post resuscitation period. Overall, hospital survival in the NCAA cohort was 21.3%. We identified 13,858 patients with linked ICU admissions in the Case Mix Programme database; 37.0% survived to hospital discharge. The incidence of IHCA peaked at 06.00. Rates of return of spontaneous circulation, survival to hospital discharge and good neurological outcome were lowest between 05.00 and 07.00. Among those admitted to ICU, no clear diurnal variation in hospital survival was seen in the unadjusted or adjusted analysis. This pattern was consistent across all presenting rhythms. CONCLUSIONS: We observed higher rates of IHCA, and poorer outcomes at night. However, in those admitted to ICU, this variation was absent. This suggests patient factors and processes of care issues contribute to the variation in IHCA seen throughout the day.

Regional citrate anticoagulation versus systemic heparin anticoagulation for continuous kidney replacement therapy in intensive care.

PURPOSE: Many intensive care units (ICUs) have transitioned from systemic heparin anticoagulation (SHA) to regional citrate anticoagulation (RCA) for continuous kidney replacement therapy (CKRT). We evaluated the clinical and health economic impacts of ICU transition to RCA. MATERIALS AND METHODS: We surveyed all adult general ICUs in England and Wales to identify transition dates and conducted a micro-costing study in eight ICUs. We then conducted an interrupted time-series analysis of linked, routinely collected health records. RESULTS: In 69,001 patients who received CKRT (8585 RCA, 60,416 SHA) in 181 ICUs between 2009 and 2017, transition to RCA was not associated with a change in 90-day mortality (adjusted odds ratio 0.98, 95% CI 0.89-1.08) but was associated with step-increases in duration of kidney support (0.53 days, 95% CI 0.28-0.79), advanced cardiovascular support (0.23 days, 95% CI 0.09-0.38) and ICU length of stay (0.86 days, 95% CI 0.24-1.49). The estimated one-year incremental net monetary benefit per patient was £ - 2376 (95% CI £ - 3841-£ - 911), with an estimated likelihood of cost-effectiveness of <0.1%. CONCLUSIONS: Transition to RCA was associated with significant increases in healthcare resource use, without corresponding clinical benefit, and is highly unlikely to be cost-effective over a one-year time horizon.

Attributable risk analysis reveals potential healthcare savings from increased consumption of dairy products.

With rising burdens of obesity and chronic disease, the role of diet as a modifiable risk factor is of increasing public health interest. There is a growing body of evidence that low consumption of dairy products is associated with elevated risk of chronic metabolic and cardiovascular disorders. Surveys also suggest that dairy product consumption falls well below recommended targets for much of the population in many countries, including the USA, UK, and Australia. We reviewed the scientific literature on the health effects of dairy product consumption (both positive and negative) and used the best available evidence to estimate the direct healthcare expenditure and burden of disease [disability-adjusted life years (DALY)] attributable to low consumption of dairy products in Australia. We implemented a novel technique for estimating population attributable risk developed for application in nutrition and other areas in which exposure to risk is a continuous variable. We found that in the 2010-2011 financial year, AUD$2.0 billion (USD$2.1 billion, €1.6 billion, or ∼1.7% of direct healthcare expenditure) and the loss of 75,012 DALY were attributable to low dairy product consumption. In sensitivity analyses, varying core assumptions yielded corresponding estimates of AUD$1.1-3.8 billion (0.9-3.3%) and 38,299-151,061 DALY lost. The estimated healthcare cost attributable to low dairy product consumption is comparable with total spending on public health in Australia (AUD$2.0 billion in 2009-2010). These findings justify the development and evaluation of cost-effective interventions that use dairy products as a vector for reducing the costs of diet-related disease.

New-onset atrial fibrillation in intensive care: epidemiology and outcomes.

AIMS: New-onset atrial fibrillation (NOAF) is common in patients treated on an intensive care unit (ICU), but the long-term impacts on patient outcomes are unclear. We compared national hospital and long-term outcomes of patients who developed NOAF in ICU with those who did not, before and after adjusting for comorbidities and ICU admission factors. METHODS AND RESULTS: Using the RISK-II database (Case Mix Programme national clinical audit of adult intensive care linked with Hospital Episode Statistics and mortality data), we conducted a retrospective cohort study of 4615 patients with NOAF and 27 690 matched controls admitted to 248 adult ICUs in England, from April 2009 to March 2016. We examined in-hospital mortality; hospital readmission with atrial fibrillation (AF), heart failure, and stroke up to 6 years post discharge; and mortality up to 8 years post discharge. Compared with controls, patients who developed NOAF in the ICU were at a higher risk of in-hospital mortality [unadjusted odds ratio (OR) 3.22, 95% confidence interval (CI) 3.02-3.44], only partially explained by patient demographics, comorbidities, and ICU admission factors (adjusted OR 1.50, 95% CI 1.38-1.63). They were also at a higher risk of subsequent hospitalization with AF [adjusted cause-specific hazard ratio (aCHR) 5.86, 95% CI 5.33-6.44], stroke (aCHR 1.47, 95% CI 1.12-1.93), and heart failure (aCHR 1.28, 95% CI 1.14-1.44) independent of pre-existing comorbidities. CONCLUSION: Patients who develop NOAF during an ICU admission are at a higher risk of in-hospital death and readmissions to hospital with AF, heart failure, and stroke than those who do not.

Child maltreatment and emergency department visits: a longitudinal birth cohort study from infancy to early adulthood.

BACKGROUND: Child maltreatment (CM) is a serious global public health issue, with documented impacts on health. OBJECTIVE: To examine the association between different levels of CM concern, and Emergency Department (ED) visits from infancy to early adulthood. PARTICIPANTS AND SETTING: Individuals born in Adelaide, South Australia from January 1986 to June 2017 (N = 443,754). METHODS: Using linked administrative data, we examined frequency and adjusted rate ratios for all-cause and cause specific ED visits among individuals with varying levels of CM concern. RESULTS: Cumulative mean ED visits to age 14.5 years were higher for individuals with any CM concern, ranging from 10.2 to 14.8, compared with 6.4 in persons with no recorded CM concern. Adjusted rate ratios for ED visits varied from 1.26 (95% CI: 1.23-1.30) to 1.54 (1.48-1.60) in children (birth to 12 years), 1.98 (CI: 1.92-2.04) to 4.34 (CI: 4.09-4.60) in adolescence and 2.22 (CI: 2.14-3.48) to 3.48 (3.27-3.72) in young adults, increasing with severity of maltreatment concerns. ED visits coded as self-harm or poisoning, injuries, substance use or mental illness were particularly high, with incidence rate ratios mostly 3 to 15 times for mental health/substance related visits and 1.5 to 3.2 for other accidents or injury for individuals with any CM concern versus none. CONCLUSIONS: The high rate ratios for ED visits in children with CM concern, especially for self-harm, substance use and mental health during adolescence and adulthood highlights the enduring mental health needs of victims of child maltreatment, providing further impetus for prevention.

Linkage of National Congenital Heart Disease Audit data to hospital, critical care and mortality national data sets to enable research focused on quality improvement.

OBJECTIVES: To link five national data sets (three registries, two administrative) and create longitudinal healthcare trajectories for patients with congenital heart disease (CHD), describing the quality and the summary statistics of the linked data set. DESIGN: Bespoke linkage of record-level patient identifiers across five national data sets. Generation of spells of care defined as periods of time-overlapping events across the data sets. SETTING: National Congenital Heart Disease Audit (NCHDA) procedures in public (National Health Service; NHS) hospitals in England and Wales, paediatric and adult intensive care data sets (Paediatric Intensive Care Audit Network; PICANet and the Case Mix Programme from the Intensive Care National Audit & Research Centre; ICNARC-CMP), administrative hospital episodes (hospital episode statistics; HES inpatient, outpatient, accident and emergency; A&E) and mortality registry data. PARTICIPANTS: Patients with any CHD procedure recorded in NCHDA between April 2000 and March 2017 from public hospitals. PRIMARY AND SECONDARY OUTCOME MEASURES: Primary: number of linked records, number of unique patients and number of generated spells of care. Secondary: quality and completeness of linkage. RESULTS: There were 143 862 records in NCHDA relating to 96 041 unique patients. We identified 65 797 linked PICANet patient admissions, 4664 linked ICNARC-CMP admissions and over 6 million linked HES episodes of care (1.1M inpatient, 4.7M outpatient). The linked data set had 4 908 153 spells of care after quality checks, with a median (IQR) of 3.4 (1.8-6.3) spells per patient-year. Where linkage was feasible (in terms of year and centre), 95.6% surgical procedure records were linked to a corresponding HES record, 93.9% paediatric (cardiac) surgery procedure records to a corresponding PICANet admission and 76.8% adult surgery procedure records to a corresponding ICNARC-CMP record. CONCLUSIONS: We successfully linked four national data sets to the core data set of all CHD procedures performed between 2000 and 2017. This will enable a much richer analysis of longitudinal patient journeys and outcomes. We hope that our detailed description of the linkage process will be useful to others looking to link national data sets to address important research priorities.

Impact of the COVID-19 pandemic on in-hospital cardiac arrests in the UK.

AIMS: To compare in-hospital cardiac arrest (IHCA) rates and patient outcomes during the first COVID-19 wave in the United Kingdom (UK) in 2020 with the same period in previous years. METHODS: A retrospective, multicentre cohort study of 154 UK hospitals that participate in the National Cardiac Arrest Audit and have intensive care units participating in the Case Mix Programme national audit of intensive care. Hospital burden of COVID-19 was defined by the number of patients with confirmed SARS-CoV2 infection admitted to critical care per 10,000 hospital admissions. RESULTS: 16,474 patients with IHCA where a resuscitation team attended were included. Patients admitted to hospital during 2020 were younger, more often male, and of non-white ethnicity compared with 2016-2019. A decreasing trend in IHCA rates between 2016 and 2019 was reversed in 2020. Hospitals with higher burden of COVID-19 had the greatest difference in IHCA rates (21.8 per 10,000 admissions in April 2020 vs 14.9 per 10,000 in April 2019). The proportions of patients achieving ROSC ≥ 20 min and surviving to hospital discharge were lower in 2020 compared with 2016-19 (46.2% vs 51.2%; and 21.9% vs 22.9%, respectively). Among patients with IHCA, higher hospital burden of COVID-19 was associated with reduced survival to hospital discharge (OR = 0.95; 95% CI 0.93 to 0.98; p < 0.001). CONCLUSIONS: In comparison with 2016-2019, the first COVID-19 wave in 2020 was associated with a higher rate of IHCA and decreased survival among patients attended by resuscitation teams. These changes were greatest in hospitals with the highest COVID-19 burden.

Hospitalizations among children involved in the child protection system: A long-term birth cohort study from infancy to adulthood using administrative data.

BACKGROUND: Despite considerable health consequences of child abuse and neglect, there is limited evidence on hospitalizations in this population. OBJECTIVES: To describe frequency and reasons for hospitalization by lifetime child protection system (CPS) involvement. PARTICIPANTS: 608,540 children born from January 1, 1986 to June 30, 2017 in South Australia, Australia METHODS: Using linked administrative data on CPS involvement and hospitalizations, we descriptively examined cumulative incidence, cumulative count and reasons for hospitalization from infancy to early adulthood by CPS involvement. RESULTS: By 16.5 years of age, cumulative incidence of ever-being hospitalized was 58% (95% CI 58-58) for children with no CPS involvement and significantly higher (72% (95% CI 71-73) to 88% (95% CI 86-90), P < 0.001) among those with different levels of CPS involvement. Cumulative mean counts of hospitalizations were highest at every age for those placed in out-of-home-care (reaching 7.7 by 16.5 years), almost four times higher than for children with no CPS involvement (2.0 by 16.5 years). Most frequent reasons for hospitalizations were similar across CPS involvement in the early years. From adolescence through early adulthood, mental health, and 'injury, poisoning or toxic effects of drugs' were frequent reasons for hospitalization among individuals with CPS involvement. CONCLUSIONS: This study highlights the vulnerability of children who have been maltreated, or are at risk of maltreatment, and the urgency of implementing effective preventive strategies early in life including consideration of adequate responses of child protection services. Frequent hospitalizations for mental health and injury confirms the potentially preventable nature of these hospitalizations.

National administrative record linkage between specialist community drug and alcohol treatment data (the National Drug Treatment Monitoring System (NDTMS)) and inpatient hospitalisation data (Hospital Episode Statistics (HES)) in England: design, method and evaluation.

OBJECTIVES: The creation and evaluation of a national record linkage between substance misuse treatment, and inpatient hospitalisation data in England. DESIGN: A deterministic record linkage using personal identifiers to link the National Drug Treatment Monitoring System (NDTMS) curated by Public Health England (PHE), and Hospital Episode Statistics (HES) Admitted Patient Care curated by National Health Service (NHS) Digital. SETTING AND PARTICIPANTS: Adults accessing substance misuse treatment in England between 1 April 2018 and 31 March 2019 (n=268 251) were linked to inpatient hospitalisation records available since 1 April 1997. OUTCOME MEASURES: Using a gold-standard subset, linked using NHS number, we report the overall linkage sensitivity and precision. Predictors for linkage error were identified, and inverse probability weighting was used to interrogate any potential impact on the analysis of length of hospital stay. RESULTS: 79.7% (n=213 814) people were linked to at least one HES record, with an estimated overall sensitivity of between 82.5% and 83.3%, and a precision of between 90.3% and 96.4%. Individuals were more likely to link if they were women, white and aged between 46 and 60. Linked individuals were more likely to have an average length of hospital stay ≥5 days if they were men, older, had no fixed residential address or had problematic opioid use. These associations did not change substantially after probability weighting, suggesting they were not affected by bias from linkage error. CONCLUSIONS: Linkage between substance misuse treatment and hospitalisation records offers a powerful new tool to evaluate the impact of treatment on substance related harm in England. While linkage error can produce misleading results, linkage bias appears to have little effect on the association between substance misuse treatment and length of hospital admission. As subsequent analyses are conducted, potential biases associated with the linkage process should be considered in the interpretation of any findings.

School Absenteeism Associated With Child Protection System Involvement, Maltreatment Type, and Time in Out-of-Home Care.

Greater school absenteeism is associated with numerous negative educational outcomes. We used a retrospective cohort design with linked administrative data on 296,422 children to examine the relationship between school absenteeism and child protection system (CPS) involvement. Children with substantiated maltreatment had 4.1 times more unexplained and problem absences than children with no CPS involvement. In multivariate analyses, children with substantiated maltreatment had significantly greater "chronic" truancy (OR = 3.41) and less "acceptable" levels of absences (OR = 0.74) compared to children with no CPS involvement. Greater absenteeism was seen for children with substantiated neglect and who had their first CPS notification earlier in life. Being in out-of-home care for 3+ years was a protective factor for children who had a CPS notification before age 5. Additional adversities had a strong additive effect with CPS involvement on absenteeism and chronic truancy. This study demonstrates the potential scope for reducing problem absenteeism and helps inform the public debate regarding how the type and timing of CPS involvement might ameliorate or exacerbate harm for children.

COVID-19 in critical care: epidemiology of the first epidemic wave across England, Wales and Northern Ireland.

PURPOSE: To describe critical care patients with COVID-19 across England, Wales and Northern Ireland and compare them with a historic cohort of patients with other viral pneumonias (non-COVID-19) and with international cohorts of COVID-19. METHODS: Extracted data on patient characteristics, acute illness severity, organ support and outcomes from the Case Mix Programme, the national clinical audit for adult critical care, for a prospective cohort of patients with COVID-19 (February to August 2020) are compared with a recent retrospective cohort of patients with other viral pneumonias (non-COVID-19) (2017-2019) and with other international cohorts of critical care patients with COVID-19, the latter identified from published reports. RESULTS: 10,834 patients with COVID-19 (70.1% male, median age 60 years, 32.6% non-white ethnicity, 39.4% obese, 8.2% at least one serious comorbidity) were admitted across 289 critical care units. Of these, 36.9% had a PaO2/FiO2 ratio of ≤ 13.3 kPa (≤ 100 mmHg) consistent with severe ARDS and 72% received invasive ventilation. Acute hospital mortality was 42%, higher than for 5782 critical care patients with other viral pneumonias (non-COVID-19) (24.7%), and most COVID-19 deaths (88.7%) occurred before 30 days. Meaningful international comparisons were limited due to lack of standardised reporting. CONCLUSION: Critical care patients with COVID-19 were disproportionately non-white, from more deprived areas and more likely to be male and obese. Conventional severity scoring appeared not to adequately reflect their acute severity, with the distribution across PaO2/FiO2 ratio categories indicating acutely severe respiratory disease. Critical care patients with COVID-19 experience high mortality and place a great burden on critical care services.

Reflections on modern methods: linkage error bias.

Linked data are increasingly being used for epidemiological research, to enhance primary research, and in planning, monitoring and evaluating public policy and services. Linkage error (missed links between records that relate to the same person or false links between unrelated records) can manifest in many ways: as missing data, measurement error and misclassification, unrepresentative sampling, or as a special combination of these that is specific to analysis of linked data: the merging and splitting of people that can occur when two hospital admission records are counted as one person admitted twice if linked and two people admitted once if not. Through these mechanisms, linkage error can ultimately lead to information bias and selection bias; so identifying relevant mechanisms is key in quantitative bias analysis. In this article we introduce five key concepts and a study classification system for identifying which mechanisms are relevant to any given analysis. We provide examples and discuss options for estimating parameters for bias analysis. This conceptual framework provides the 'links' between linkage error, information bias and selection bias, and lays the groundwork for quantitative bias analysis for linkage error.

Lifetime risk of child protection system involvement in South Australia for Aboriginal and non-Aboriginal children, 1986-2017 using linked administrative data.

BACKGROUND: Child protection services exist to reduce potential harms from child maltreatment. Many jurisdictions produce annual data on child protection system (CPS) involvement, leaving a gap in knowledge of lifetime involvement. OBJECTIVE: To describe lifetime involvement in CPS, by type of contact. PARTICIPANTS: All 608,547 children born in South Australia (SA), Australia between 1986 and 2017. METHODS: A retrospective cohort design using linked administrative data to report cumulative incidence of CPS involvement from birth to age <18 (or June30 2017) by Aboriginal status. CPS involvement was categorised into notifications (3 levels), investigations, substantiations and out-of-home care (OOHC). Cumulative incidence curves were derived for 5 birth cohorts. RESULTS: Across childhood (to age <18 years), substantiated maltreatment was experienced by 3.2-3.6% of non-Aboriginal and 19-25% of Aboriginal children, 7 times reported annual substantiation rates. For most CPS categories CPS involvement increased until 2010, and was occurring earlier in life. By age 3, 0.5% of non-Aboriginal and 4.5% of Aboriginal children born 1986-1991 were the subject of a substantiation compared with 1.9% and 15% of non-Aboriginal and Aboriginal children, respectively, born 2010-2017. Incidence rates beyond age 3 were similar. OOHC contact was similar across cohorts, with ˜1.5% of non-Aboriginal and 12.7% of Aboriginal children ever-placed in care. CONCLUSIONS: Data linkage is an essential tool for understanding life course involvement with the CPS and describing trends not observable from annual snapshots. Such information is critical for burden of disease estimates, informing policy and monitoring CPS performance.