Association Between ABO and Rh Blood Groups and SARS-CoV-2 Infection or Severe COVID-19 Illness : A Population-Based Cohort Study.

BACKGROUND: The ABO and rhesus (Rh) blood groups may influence risk for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. OBJECTIVE: To determine whether ABO and Rh blood groups are associated with risk for SARS-CoV-2 infection and severe coronavirus disease 2019 (COVID-19) illness. DESIGN: Population-based cohort study. SETTING: Ontario, Canada. PATIENTS: All adults and children who had ABO blood group assessed between January 2007 and December 2019 and who subsequently had SARS-CoV-2 testing between 15 January and 30 June 2020. MEASUREMENTS: The main study outcome was SARS-CoV-2 infection, determined by viral RNA polymerase chain reaction testing. A second outcome was severe COVID-19 illness or death. Adjusted relative risks (aRRs) and absolute risk differences (ARDs) were adjusted for demographic characteristics and comorbidities. RESULTS: A total of 225 556 persons were included, with a mean age of 54 years. The aRR of SARS-CoV-2 infection for O blood group versus A, AB, and B blood groups together was 0.88 (95% CI, 0.84 to 0.92; ARD, -3.9 per 1000 [CI, -5.4 to -2.5]). Rhesus-negative (Rh-) blood type was protective against SARS-CoV-2 infection (aRR, 0.79 [CI, 0.73 to 0.85]; ARD, -6.8 per 1000 [CI, -8.9 to -4.7]), especially for those who were O-negative (O-) (aRR, 0.74 [CI, 0.66 to 0.83]; ARD, -8.2 per 1000 [CI, -10.8 to -5.3]). There was also a lower risk for severe COVID-19 illness or death associated with type O blood group versus all others (aRR, 0.87 [CI, 0.78 to 0.97]; ARD, -0.8 per 1000 [CI, -1.4 to -0.2]) and with Rh- versus Rh-positive (aRR, 0.82 [CI, 0.68 to 0.96]; ARD, -1.1 per 1000 [CI, -2.0 to -0.2]). LIMITATION: Persons who rapidly died of severe COVID-19 illness may not have had SARS-CoV-2 testing. CONCLUSION: The O and Rh- blood groups may be associated with a slightly lower risk for SARS-CoV-2 infection and severe COVID-19 illness. PRIMARY FUNDING SOURCE: Ontario Academic Health Sciences Centre AFP Innovation Fund and the Ontario Ministry of Health and Long-Term Care.

Maternal Origin and Risk of Neonatal and Maternal ICU Admission.

OBJECTIVES: To evaluate maternal world region of birth, as well as maternal country of origin, and the associated risk of admission of 1) a mother to a maternal ICU, 2) her infant to a neonatal ICU, or 3) both concurrently to an ICU. DESIGN: Retrospective population-based cohort study. SETTING: Entire province of Ontario, Canada, from 2003 to 2012. PATIENTS: All singleton maternal-child pairs who delivered in any Ontario hospital. MEASUREMENTS AND MAIN RESULTS: We explored how maternal world region of birth, and specifically, maternal country of birth for the top 25 countries, was associated with the outcome of 1) neonatal ICU, 2) maternal ICU, and 3) both mother and newborn concurrently admitted to ICU. Relative risks were adjusted for maternal age, parity, income quintile, chronic hypertension, diabetes mellitus, obesity, dyslipidemia, drug dependence or tobacco use, and renal disease. Compared with infants of Canadian-born mothers (110.7/1,000), the rate of neonatal ICU admission was higher in immigrants from South Asia (155.2/1,000), Africa (140.4/1,000), and the Caribbean (167.3/1,000; adjusted relative risk, 1.41; 95% CI, 1.36-1.46). For maternal ICU, the adjusted relative risk was 1.79 (95% CI, 1.43-2.24) for women from Africa and 2.21 (95% CI, 1.78-2.75) for women from the Caribbean. Specifically, mothers from Ghana (adjusted relative risk, 2.71; 95% CI, 1.75-4.21) and Jamaica (adjusted relative risk, 2.74; 95% CI, 2.12-3.53) were at highest risk of maternal ICU admission. The risk of both mother and newborn concurrently admitted to ICU was even more pronounced for Ghana and Jamaica. CONCLUSIONS: Women from Africa and the Caribbean and, in particular, Ghana and Jamaica, are at higher risk of admission to ICU around the time of delivery, as are their newborns.

Prognosis after maternal placental events and revascularization: PAMPER study.

BACKGROUND: Middle-aged women are at higher risk than men of death after coronary artery revascularization. Maternal placental syndromes (gestational hypertension, preeclampsia, placental abruption, and placental infarction) are associated with premature coronary artery disease, but their influence on survival after coronary artery revascularization is unknown. OBJECTIVE: The purpose of this study was to determine whether a history of maternal placental syndromes alters the risk of death after coronary artery revascularization in middle-aged women. STUDY DESIGN: We completed a population-based retrospective cohort study among all hospitals in Ontario, Canada, where universal health care includes all aspects of antenatal and delivery care as well as all outpatient and inpatient health care, which includes coronary revascularization. We included 1985 middle-aged women who underwent a first percutaneous coronary intervention or coronary artery bypass grafting between 1993 and 2012 and who had ≥1 previous delivery. We excluded those with cardiovascular disease ≤1 year before or coronary revascularization ≤90 days after any delivery. The main study outcome, determined a priori, was all-cause death. Hazard ratios were adjusted for age, socioeconomic status, parity, revascularization type, time since last delivery, hypertension, diabetes mellitus, obesity, dyslipidemia, tobacco or drug dependence, and kidney disease. RESULTS: Three hundred sixty-two of 1985 women (18.2%) who underwent coronary artery revascularization had a previous maternal placental syndrome event. The mean age at index coronary revascularization was 45 years; percutaneous coronary intervention comprised approximately 80% of procedures. After a mean follow-up time of approximately 5 years, 41 deaths (2.2 per 100 person-years) occurred in women with previous maternal placental syndromes and 83 deaths (1.1 per 100 person-years) in women without maternal placental syndrome (adjusted hazard ratio, 1.96; 95% confidence interval, 1.29-2.99). Of the maternal placental syndrome subtypes, the risk of death was significant in women with placental abruption (adjusted hazard ratio, 2.79; 95% confidence interval, 1.31-5.96), placental infarction (adjusted hazard ratio, 3.09; 95% confidence interval, 1.23-7.74), and preeclampsia (adjusted hazard ratio, 1.61; 95% confidence interval, 1.00-2.58). Women with maternal placental syndrome in ≥2 pregnancies had the highest adjusted hazard ratio of death (4.31; 95% confidence interval, 1.71-10.89). CONCLUSION: In middle-aged women who undergo coronary revascularization, previous maternal placental syndrome doubles the risk of death; recurrent maternal placental syndrome quadruples that risk. Some covariates and secondary measures may not have been well-captured and classified herein, leading to residual confounding.

The Effect of Pay for Performance in the Emergency Department on Patient Waiting Times and Quality of Care in Ontario, Canada: A Difference-in-Differences Analysis.

STUDY OBJECTIVE: In 2008, a pay-for-performance program was implemented in sequential waves in Ontario emergency departments (EDs), with the aim of reducing length of stay. We seek to evaluate its effects on ED length of stay and quality of care. METHODS: This was a retrospective observational study of ED visits in Ontario from April 1, 2007, to March 31, 2011, using multivariable difference-in-differences analysis. Pay-for-performance hospitals and matched control sites were selected for each of 3 waves of the program. The primary outcome was 90th percentile ED length of stay; we also examined quality-of-care indicators. RESULTS: Pay-for-performance hospitals had a modest reduction in overall adjusted 90th percentile ED length of stay in wave 1 (-36 minutes; 95% confidence interval [CI] -50 to -21 minutes), but not in wave 2 (-14 minutes; 95% CI -30 to 2 minutes) or wave 3 (-7 minutes; 95% CI -23 to 8 minutes). ED admitted patients had a pronounced reduction in adjusted 90th percentile length of stay in wave 1 (-225 minutes; 95% CI -263 to -188 minutes) and wave 2 (-133 minutes; 95% CI -175 to -91 minutes). Nonadmitted low-acuity patients had reductions in adjusted 90th percentile ED length of stay in wave 1 (-24 minutes; 95% CI -29 to -18 minutes) and wave 3 (-19 minutes; 95% CI -24 to -14 minutes). The program did not negatively affect ED quality-of-care measures, such as 30-day mortality or readmission rates. CONCLUSION: Pay-for-performance was associated with modest overall benefits for ED length of stay without adversely affecting quality of care.

Association Between MRI Exposure During Pregnancy and Fetal and Childhood Outcomes.

IMPORTANCE: Fetal safety of magnetic resonance imaging (MRI) during the first trimester of pregnancy or with gadolinium enhancement at any time of pregnancy is unknown. OBJECTIVE: To evaluate the long-term safety after exposure to MRI in the first trimester of pregnancy or to gadolinium at any time during pregnancy. DESIGN, SETTING, AND PARTICIPANTS: Universal health care databases in the province of Ontario, Canada, were used to identify all births of more than 20 weeks, from 2003-2015. EXPOSURES: Magnetic resonance imaging exposure in the first trimester of pregnancy, or gadolinium MRI exposure at any time in pregnancy. MAIN OUTCOMES AND MEASURES: For first-trimester MRI exposure, the risk of stillbirth or neonatal death within 28 days of birth and any congenital anomaly, neoplasm, and hearing or vision loss was evaluated from birth to age 4 years. For gadolinium-enhanced MRI in pregnancy, connective tissue or skin disease resembling nephrogenic systemic fibrosis (NSF-like) and a broader set of rheumatological, inflammatory, or infiltrative skin conditions from birth were identified. RESULTS: Of 1 424 105 deliveries (48% girls; mean gestational age, 39 weeks), the overall rate of MRI was 3.97 per 1000 pregnancies. Comparing first-trimester MRI (n = 1737) to no MRI (n = 1 418 451), there were 19 stillbirths or deaths vs 9844 in the unexposed cohort (adjusted relative risk [RR], 1.68; 95% CI, 0.97 to 2.90) for an adjusted risk difference of 4.7 per 1000 person-years (95% CI, -1.6 to 11.0). The risk was also not significantly higher for congenital anomalies, neoplasm, or vision or hearing loss. Comparing gadolinium MRI (n = 397) with no MRI (n = 1 418 451), the hazard ratio for NSF-like outcomes was not statistically significant. The broader outcome of any rheumatological, inflammatory, or infiltrative skin condition occurred in 123 vs 384 180 births (adjusted HR, 1.36; 95% CI, 1.09 to 1.69) for an adjusted risk difference of 45.3 per 1000 person-years (95% CI, 11.3 to 86.8). Stillbirths and neonatal deaths occurred among 7 MRI-exposed vs 9844 unexposed pregnancies (adjusted RR, 3.70; 95% CI, 1.55 to 8.85) for an adjusted risk difference of 47.5 per 1000 pregnancies (95% CI, 9.7 to 138.2). CONCLUSIONS AND RELEVANCE: Exposure to MRI during the first trimester of pregnancy compared with nonexposure was not associated with increased risk of harm to the fetus or in early childhood. Gadolinium MRI at any time during pregnancy was associated with an increased risk of a broad set of rheumatological, inflammatory, or infiltrative skin conditions and for stillbirth or neonatal death. The study may not have been able to detect rare adverse outcomes.

Increasing Access to Health Administrative Data with ICES Data & Analytic Services.

The Institute for Clinical Evaluative Sciences (ICES) is one of only a few organizations in Ontario permitted to access, link and analyze health administrative data for the purpose of generating evidence to inform decisions in policy and practice. Although ICES is a leading research institute, its access to the data has historically been restricted to scientists with an ICES affiliation. This requirement, designed to meet ICES' data privacy and security obligations, created barriers with respect to the widespread use of Ontario's data assets. In 2014, as part of the government's commitment to the Strategy for Patient-Oriented Research, ICES launched the Data & Analytic Services platform, which is aimed at increasing access to data and analytic services to investigators external to ICES. In making the data widely available to the broader research community, this initiative engages investigators involved in front-line care, stimulates new avenues of research and fosters collaboration that was previously challenging or unfeasible.

Repeated emergency department visits among children admitted with meningitis or septicemia: a population-based study.

STUDY OBJECTIVE: Early diagnosis of children with meningitis or septicemia remains a significant challenge in emergency medicine. We seek to describe the frequency of repeated emergency department (ED) visits among children admitted with meningitis or septicemia in Ontario, Canada. METHODS: In this retrospective cohort study, using health administrative data, we included all children aged 30 days to 5 years who were hospitalized with a final diagnosis of meningitis or septicemia in Ontario between 2005 and 2010. ED visits at any hospital in the preceding 5 days were identified as potential repeated ED visits. We used generalized estimating equations to model the association of sex, age, triage score, immunocompromised state, visit timing, type of ED, and annual patient volume on the risk of repeated ED visits. RESULTS: Of 521 children, 114 (21.9%) had repeated ED visits before admission. Children admitted on initial visit and those with repeated visits had similar median lengths of stay (13 versus 12 days), critical care use (21.1% versus 16.7%), and mortality (mean 2.9%). One in 3 children repeating visits returned to a different hospital. Repeated visits were associated with older age, a less acute triage score, and initial visit to a community hospital without available pediatric consultation. CONCLUSION: In this cohort, repeated ED visits among children with meningitis or septicemia were common, yet they had health outcomes similar to those of children admitted on initial visit. One in 3 returned to a different ED, making it unlikely that EDs and clinicians can learn from these critical events without a regionalized reporting system.

Evaluation of an emergency department lean process improvement program to reduce length of stay.

STUDY OBJECTIVE: In recent years, lean principles have been applied to improve wait times in the emergency department (ED). In 2009, an ED process improvement program based on lean methods was introduced in Ontario as part of a broad strategy to reduce ED length of stay and improve patient flow. This study seeks to determine the effect of this program on ED wait times and quality of care. METHODS: We conducted a retrospective cohort study of all ED visits at program and control sites during 3 program waves from April 1, 2007, to June 30, 2011, in Ontario, Canada. Time series analyses of outcomes before and after the program and difference-in-differences analyses comparing changes in program sites with control sites were conducted. RESULTS: In before-after models among program sites alone, 90th percentile ED length of stay did not change in wave 1 (-14 minutes [95% confidence interval {CI} -47 to 20]) but decreased after wave 2 (-87 [95% CI -108 to -66]) and wave 3 (-33 [95% CI -50 to -17]); median ED length of stay decreased after wave 1 (-18 [95% CI -24 to -12]), wave 2 (-23 [95% CI -27 to -19]), and wave 3 (-15 [95% CI -18 to -12]). In all waves, decreases were observed in time to physician assessment, left-without-being-seen rates, and 72-hour ED revisit rates. In the difference-in-difference models, in which changes in program sites were compared with controls, the program was associated with no change in 90th percentile ED length of stay in wave 2 (17 [95% CI -0.2 to 33]) and increases in wave 1 (23 [95% CI 0.9 to 45]) and wave 3 (31 [95% CI 10 to 51]), modest reductions in median ED length of stay in waves 2 and 3 alone, and a decrease in time to physician assessment in wave 3 alone. CONCLUSION: Although the program reduced ED waiting times, it appeared that its benefits were diminished or disappeared when compared with that of control sites, which were exposed to system-wide initiatives such as public reporting and pay for performance. This study suggests that further evaluation of the effectiveness of lean methods in the ED is warranted before widespread implementation.

Emergency department computed tomography utilization in the United States and Canada.

STUDY OBJECTIVE: We compare secular trends in computed tomography (CT) utilization in emergency departments (EDs) in the United States and Ontario, Canada. METHODS: Using a systematic survey in the US (The National Hospital Ambulatory Medical Care Survey) and administrative databases in Ontario, we performed a retrospective study of ED visits from 2003 to 2008. We calculated utilization overall, by visit characteristics, and for 5 clinical conditions in which CT is commonly indicated: abdominal pain, complex abdominal pain (abdominal pain, age ≥65 years, urgent to most urgent triage), admitted complex abdominal pain (abdominal pain, age ≥65 years, urgent to most urgent triage, and admitted to hospital), headache, and chest pain/shortness of breath. US data were weighted to produce national estimates. RESULTS: On-site CT was available for 97% (95% confidence interval [CI] 95% to 99%) of visits in the United States compared with 80% (95% CI 80% to 80%) in Ontario. Visits were more frequently triaged as higher acuity in the United States than in Ontario, with 15.1% (95% CI 13.9% to 16.4%) of US visits categorized as most urgent versus 11.8% (95% CI 11.8% to 11.8%) in Ontario. The proportion of all ED visits in which CT was performed was 11.4% (95% CI 10.8% to 12.0%) in the United States versus 5.9% (95% CI 5.9% to 5.9%) in Ontario. The proportion for children was 4.7% (95% CI 4.3% to 5.1%) in the United States versus 1.4% (95% CI 1.4% to 1.4%) in Ontario. The rate of visits involving CT per year increased faster from 2003 to 2008 in the United States (odds ratio 2.00; 95% CI 1.81 to 2.21) than Ontario (odds ratio 1.69; 95% CI 1.68 to 1.70). Over time, all subgroups experienced increases in CT rate except Ontario children younger than 10 years, who experienced a significant decrease. United States-Ontario differences in CT proportions were significant among patients presenting with headache, abdominal pain, chest pain/shortness of breath, and complex abdominal pain. Proportions for visits involving admitted complex abdominal pain in the two jurisdictions were indistinguishable: 45.8% in the United States (95% CI 39.9% to 51.7%) versus 44.7% (95% CI 44.4% to 45.0%) in Ontario. CONCLUSION: CT was more readily available in US EDs, and US clinicians used the technology more frequently than their colleagues in Ontario for nearly every category of patients, including children. CT utilization increased over time in both jurisdictions, but faster in the United States. Different demographic features between the two jurisdictions, including triage severity, frequency of hospitalization, and availability of CT scanners, likely account for at least some of the differences in CT utilization. Investigation of both clinical and nonclinical reasons for the differences in CT utilization between the United States and Canada would be a fruitful area for further research.

Maternal and neonatal separation and mortality associated with concurrent admissions to intensive care units.

BACKGROUND: Concurrent admission of a mother and her newborn to separate intensive care units (herein referred to as co-ICU admission), possibly in different centres, can magnify family discord and stress. We examined the prevalence and predictors of mother-infant separation and mortality associated with co-ICU admissions. METHODS: We completed a population-based study of all 1 023 978 singleton live births in Ontario between Apr. 1, 2002, and Mar. 31, 2010. We included data for maternal-infant pairs that had co-ICU admission (n = 1216), maternal ICU admission only (n = 897), neonatal ICU (NICU) admission only (n = 123 236) or no ICU admission (n = 898 629). The primary outcome measure was mother-infant separation because of interfacility transfer. RESULTS: The prevalence of co-ICU admissions was 1.2 per 1000 live births and was higher than maternal ICU admissions (0.9 per 1000). Maternal-newborn separation due to interfacility transfer was 30.8 (95% confidence interval [CI] 26.9-35.3) times more common in the co-ICU group than in the no-ICU group and exceeded the prevalence in the maternal ICU group and NICU group. Short-term infant mortality (< 28 days after birth) was higher in the co-ICU group (18.1 per 1000 live births; maternal age-adjusted hazard ratio [HR] 27.8, 95% CI 18.2-42.6) than in the NICU group (7.6 per 1000; age-adjusted HR 11.5, 95% CI 10.4-12.7), relative to 0.7 per 1000 in the no-ICU group. Short-term maternal mortality (< 42 days after delivery) was also higher in the co-ICU group (15.6 per 1000; age-adjusted HR 328.7, 95% CI 191.2-565.2) than in the maternal ICU group (6.7 per 1000; age-adjusted HR 140.0, 95% CI 59.5-329.2) or the NICU group (0.2 per 1000; age-adjusted HR 4.6, 95% CI 2.8-7.4). INTERPRETATION: Mother-infant pairs in the co-ICU group had the highest prevalence of separation due to interfacility transfer and the highest mortality compared with those in the maternal ICU and NICU groups.

Non-ABO red cell antibodies and risk of COVID-19.

It is not known whether non-ABO antibodies confer any protective effect against SARS-CoV-2 infection or COVID-19 severe illness alone or in conjunction with O blood group. This cohort study included 413 576 persons in Ontario, Canada with known ABO blood group and non-ABO antibody screen status, who subsequently underwent SARS-CoV-2 viral RNA polymerase chain reaction testing between January and November 2020. The risk of SARS-CoV-2 infection or COVID-19 severe illness was not associated with the presence of non-ABO antibodies, even among persons with O blood group.

Major radiodiagnostic imaging in pregnancy and the risk of childhood malignancy: a population-based cohort study in Ontario.

BACKGROUND: The association between fetal exposure to major radiodiagnostic testing in pregnancy-computed tomography (CT) and radionuclide imaging-and the risk of childhood cancer is not established. METHODS AND FINDINGS: We completed a population-based study of 1.8 million maternal-child pairs in the province of Ontario, from 1991 to 2008. We used Ontario's universal health care-linked administrative databases to identify all term obstetrical deliveries and newborn records, inpatient and outpatient major radiodiagnostic services, as well as all children with a malignancy after birth. There were 5,590 mothers exposed to major radiodiagnostic testing in pregnancy (3.0 per 1,000) and 1,829,927 mothers not exposed. The rate of radiodiagnostic testing increased from 1.1 to 6.3 per 1,000 pregnancies over the study period; about 73% of tests were CT scans. After a median duration of follow-up of 8.9 years, four childhood cancers arose in the exposed group (1.13 per 10,000 person-years) and 2,539 cancers in the unexposed group (1.56 per 10,000 person-years), a crude hazard ratio of 0.69 (95% confidence interval 0.26-1.82). After adjusting for maternal age, income quintile, urban status, and maternal cancer, as well as infant sex, chromosomal or congenital anomalies, and major radiodiagnostic test exposure after birth, the risk was essentially unchanged (hazard ratio 0.68, 95% confidence interval 0.25-1.80). CONCLUSIONS: Although major radiodiagnostic testing is now performed in about 1 in 160 pregnancies in Ontario, the absolute annual risk of childhood malignancy following exposure in utero remains about 1 in 10,000. Since the upper confidence limit of the relative risk of malignancy may be as high as 1.8 times that of an unexposed pregnancy, we cannot exclude the possibility that fetal exposure to CT or radionuclide imaging is carcinogenic.

Trajectories of health system use and survival for community-dwelling persons with dementia: a cohort study.

OBJECTIVES: To determine the long-term trajectories of health system use by persons with dementia as they remain in the community over time. DESIGN: Population-based cohort study using health administrative data. SETTING: Ontario, Canada from 1 April 2007 to 31 March 2014. PARTICIPANTS: 62 622 community-dwelling adults aged 65+ years with prevalent dementia on 1 April 2007 matched 1:1 to persons without dementia based on age, sex and comorbidity. MAIN OUTCOME MEASURES: Rates of health service use, long-term care placement and mortality over time. RESULTS: After 7 years, 49.0% of persons with dementia had spent time in long-term care (6.8% without) and 64.5% had died (30.0% without). Persons with dementia were more likely than those without to use home care (rate ratio (RR) 3.02, 95% CI 2.93 to 3.11) and experience hospitalisations with a discharge delay (RR 2.36, 95% CI 2.30 to 2.42). As they remained in the community, persons with dementia used home care at a growing rate (10.7%, 95% CI 10.0 to 11.3 increase per year vs 6.7%, 95% CI 4.3 to 9.0 per year among those without), but rates of acute care hospitalisation remained constant (0.6%, 95% CI -0.6 to 1.9 increase per year). CONCLUSIONS: While persons with dementia used more health services than those without dementia over time, the rate of change in use differed by service type. These results, particularly enumerating the increased intensity of home care service use, add value to capacity planning initiatives where limited budgets require balancing services.

Pivoting data and analytic capacity to support Ontario's COVID-19 response.

Introduction: Health care systems have faced unprecedented challenges due to the COVID-19 pandemic. Access to timely population-based data has been vital to informing public health policy and practice. Methods: We describe how ICES, an independent not-for-profit research and analytic institute in Ontario, Canada, pivoted existing research infrastructure and engaged health system stakeholders to provide near real-time population-based data and analytics to support Ontario's COVID-19 pandemic response. Results: Since April 2020, ICES provided the Ontario COVID-19 Provincial Command Table and public health partners with regular and ad hoc reports on SARS-CoV-2 testing and COVID-19 vaccine coverage. These reports: 1) helped identify congregate care/shared living settings that needed testing and prevention efforts early in the pandemic; 2) provided early indications of inequities in testing and infection in marginalized neighbourhoods, including areas with higher proportions of immigrants and visible minorities; 3) identified areas with high test positivity, which helped Public Health Units target and evaluate prevention efforts; and 4) contributed to altering the province's COVID-19 vaccine roll-out strategy to target high-risk neighbourhoods and helping Public Health Units and community organizations plan local vaccination programs. In addition, ICES is a key component of the Ontario Health Data Platform, which provides scientists with data access to conduct COVID-19 research and analyses. Discussion and Conclusion: ICES was well-positioned to provide rapid analyses for decision-makers to respond to the evolving public health emergency, and continues to contribute to Ontario's pandemic response by providing timely, relevant reports to health system stakeholders and facilitating data access for externally-funded COVID-19 research.

Disequilibrium between admitted and discharged hospitalized patients affects emergency department length of stay.

STUDY OBJECTIVE: Most patients are admitted to the hospital through the emergency department (ED), and ED waiting times partly reflect the availability of inpatient beds. We test whether the balance between daily hospital admissions and discharges affects next-day ED length of stay. METHODS: We conducted a cross-sectional study of hospitals in metropolitan Toronto, served by a single emergency medical services provider in a publicly funded system. During a 3-year period, we evaluated the daily ratio of admissions to discharges at each hospital and the next-day median ED length of stay in the same hospital by using linear regression. RESULTS: Across hospitals, the daily mean (SD) 50th percentile ED length of stay averaged 218 (51) minutes. As the inpatient admission-discharge ratio increased or decreased, next-day ED length of stay changed accordingly. Compared with ratios of 1.0, those less than 0.6 were associated with an 11-minute (95% confidence interval [CI] 5 to 16 minutes) shorter next-day median ED length of stay; at admission-discharge ratios of 1.3 to 1.4, ED length of stay was significantly prolonged by 5 minutes (95% CI 3 to 6 minutes). Admission-discharge ratios on weekends and among medical inpatients had a stronger influence on next-day ED length of stay; effects were also greater among higher-acuity and admitted ED patients. CONCLUSION: Disequilibrium between the number of admitted and discharged inpatients significantly affects next-day ED length of stay. Better matching of daily hospital discharges and admissions could reduce ED waiting times and may be more amenable to intervention than reducing admissions alone. The admission-discharge ratio may also provide a simple way of tracking and enhancing hospital system performance.

Health impact of hospital restrictions on seriously ill hospitalized patients: lessons from the Toronto SARS outbreak.

BACKGROUND: Restrictions on non-urgent hospital care imposed to control the 2003 Toronto severe acute respiratory syndrome outbreak led to substantial disruptions in hospital clinical practice, admission, and transfer patterns. OBJECTIVES: We assessed whether there were unintended health consequences to seriously ill hospitalized patients. STUDY DESIGN, SETTING, AND POPULATION: Population-based longitudinal cohort study of patients residing in Toronto or an urban control region with an incident admission for 1 of 7 serious conditions in the 3 years before, or the 4 months during or after restrictions. OUTCOME MEASURES: Short-term mortality, overall readmissions, cardiac readmissions for acute myocardial infarction patients, serious complications for very low birth weight babies, and quality of care measures, comparing adjusted rates across time periods within regions. RESULTS: Mortality, readmission, and complication rates did not change for any condition during or after severe acute respiratory syndrome restrictions. Although rates of invasive cardiac procedures for acute myocardial infarction patients decreased 11-37% in Toronto, rates of nonfatal cardiac outcomes did not change. CONCLUSIONS: Restrictions on non-urgent hospital utilization and hospital transfers may be a safe public health strategy to employ to control nosocomial outbreaks or provide hospital surge capacity for up to several months, in large, well-developed healthcare systems with good availability of community-based care.

Maternal obesity and the risk of placental vascular disease.

INTRODUCTION: While elevated maternal weight in early pregnancy is associated with a higher rate of preeclampsia, the risk of placental abruption and placental infarction is unknown. METHODS: We evaluated the risk of placental abruption, placental infarction, and preeclampsia in association with maternal weight quintile at approximately 17 weeks' gestation in 386 323 women with a singleton pregnancy who underwent maternal serum screening in Ontario. RESULTS: After adjusting for age, ethnicity, parity, diabetes mellitus, and tobacco use, the odds ratio (OR) for preeclampsia was 4.1 (95% confidence interval [CI] 3.8-4.4) comparing the highest and lowest weight quintiles. Conversely, there was a lower risk of placental abruption or placental infarction, despite further adjustment for preeclampsia, gestational hypertension and drug dependence (OR 0.81, 95% CI 0.75-0.87). CONCLUSION: Higher maternal weight in early pregnancy is associated with a higher risk of preeclampsia and a lower risk of placental abruption or placental infarction, a seeming paradox that requires further elucidation.

Missed diagnosis of subarachnoid hemorrhage in the emergency department.

BACKGROUND AND PURPOSE: Subarachnoid hemorrhage (SAH) can be devastating, yet its initial presentation may be limited to common symptoms and subtle signs, potentially leading to misdiagnosis. Little is known about population rates of misdiagnosis of SAH, or hospital factors that may contribute to it. We estimated the population-based rate of missed SAH among emergency department (ED) patients and examined its relationship with hospital characteristics. METHODS: We studied persons admitted with a nontraumatic SAH to all Ontario hospitals over 3 years (April 2002 to March 2005). SAH was defined as missed if the patient had an ED visit related to the SAH (based on a prespecified definition) in the 14 days before admission. We examined the association between hospital teaching status and missed SAH and explored whether annual ED volume of SAH or CT availability explained this association. RESULTS: Of 1507 patients diagnosed with SAH, 5.4% (95% CI, 4.3 to 6.6) had a missed diagnosis. The risk was significantly higher among patients triaged as low acuity (odds ratio 2.65; 95% CI, 1.46 to 4.80), as well as in nonteaching hospitals (adjusted odds ratio 2.12; 95% CI, 1.02, 4.44). Neither ED SAH volume nor on-site CT availability explained the effect of teaching status. CONCLUSIONS: About 1 in 20 SAH patients are missed during an ED visit. Lower acuity patients are at higher risk of misdiagnosis, suggesting the need for heightened suspicion among patients with minimal clinical findings. The risk is also greater in nonteaching hospitals, but this is not explained by the annual volume of SAHs seen in the ED or access to CT.

ICD-10 adaptations of the Ontario acute myocardial infarction mortality prediction rules performed as well as the original versions.

OBJECTIVE: To derive and validate an International Classification of Diseases-10 (ICD-10) version of the Ontario Acute Myocardial Infarction (AMI) mortality prediction rules, used to adjust for case-mix differences in studies of AMI patients using administrative data. STUDY DESIGN AND SETTING: We linked the records of all Ontario patients admitted with AMI (2002-2004) with mortality data. The original ICD-9 codes were mapped to ICD-10-CA (Canada) codes using both a translation produced by coding experts and a manual search of codes; the final codes were determined by consensus. Comorbidity prevalence and mortality rates were calculated. Multivariable logistic regression models were used to predict 30-day and 1-year mortality and the C-statistic was used to evaluate the discrimination of the models. RESULTS: We identified 37,271 AMI patients. The most common comorbidities were heart failure and dysrhythmias; 30-day and 1-year mortality rates were 12.3% and 21.8%, respectively; and mortality rates were highest among patients with shock, cancer, and acute renal failure. The C-statistics were 0.77 and 0.80, compared with 0.78 and 0.79 in the ICD-9 version, for 30-day and 1-year mortality, respectively. CONCLUSION: An ICD-10 version of the AMI mortality prediction rules predicted 30-day and 1-year mortality as well as the original ICD-9 version.