key: cord-0854771-f0fkclg0
authors: Wai, Abraham K.C.; Wong, Carlos K.H.; Wong, Janet Y.H.; Xiong, Xi; Chu, Owen C.K.; Wong, Man Sing; Tsui, Matthew S.H.; Rainer, Timothy H.
title: Changes in emergency department visits, diagnostic groups and 28-day mortality associated with the COVID-19 pandemic: a territory-wide, retrospective, cohort study
date: 2021-09-24
journal: Ann Emerg Med
DOI: 10.1016/j.annemergmed.2021.09.424
sha: e653a57f3e9b92bf6826f1cbfeffe42ef96b4be8
doc_id: 854771
cord_uid: f0fkclg0

Objective We aimed to evaluate and characterize the scale and relationships of emergency department visits and excess mortality associated with the early phase of COVID-19 pandemic for the territory of Hong Kong. Methods We conducted a territory-wide, retrospective, cohort study to compare the ED visits and related impact of the COVID-19 pandemic on mortality. All ED visits at 18 public acute hospitals in Hong Kong between January 1st and August 31st, 2019 (n=1,426,259); and 2020 (n=1,035,562) were included. The primary outcome was all-cause mortality in the 28 days following an ED visits. The secondary outcomes were weekly number of ED visits and diagnosis-specific mortality. Results ED visits decreased by 27.4% from 1,426,259 in 2019 to 1,035,562 in 2020. Overall period mortality increased from 28,686 (2.0%) in 2019 to 29,737 (2.9%) in 2020. The adjusted odds ratio (OR) for 28-day, all-cause mortality in the pandemic period of 2020 relative to 2019 was 1.26 (95%CI 1.24-1.28). Both genders, age >45 years, all triage categories, all social classes, ED visits periods and for epilepsy (OR 1.58, 95%CI 1.20-2.07), lower respiratory tract infection and airway disease had higher adjusted ORs for all-cause mortality. Conclusions A significant reduction in ED visits in the first eight months of the COVID-19 pandemic was associated with an increase in deaths certified in ED. Government must make provision to encourage patients with alarming symptoms, mental health conditions and co-morbidities to seek timely emergency care, regardless of the pandemic.

Coronavirus Disease-2019 (COVID- 19) represents the third coronavirus-associated epidemic to emerge from a species leap from wild animals to humans. 1, 2 The coronavirus causes a spectrum of presentations from asymptomatic through mild disease with respiratory symptoms to lifethreatening acute respiratory illness. 3, 4 By the end of 2020, worldwide there were at least 80 million cases with positive Systemic Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV2) serology and over 1.5 million reported SARS-CoV2-associated deaths. 5

Emergency departments (ED) are on the frontline of the COVID-19 pandemic and need to manage both COVID and the full spectrum of non-COVID cases such as myocardial infarction, 6 acuteonset leukemia 7 and trauma and injuries. 8 In some jurisdictions reduced hospital visits helped alleviate the rising pressure on the health systems due to the pandemic. For example, there was a reduction in total ED visits in the United States (US), 9 United Kingdom (UK) 10 and Spain. 8 In the US, reductions in ED visits ranged from 41.5% in Colorado to 63.5% in New York. 11 The factors contributing to these reductions await clarification. However, the early message in the UK was that the system was under huge pressure and that there was a need to 'Protect the National Health Service (NHS)'. 12 It is likely that fear of the virus, concern that hospitals may not be healthy and safe places and a strong public health message discouraging 'unnecessary' ED visits contributed to some of the reductions.

The reduced hospital and ED visits during the pandemic outside Hong Kong included patients with heart attacks (23%), strokes (20%) and hyperglycemic crises (10%). 13 Increased non-COVID mortality affected patients with heart disease, 14 Alzheimer disease and dementia. 15 In general these J o u r n a l P r e -p r o o f reports reflect communities that were directly overwhelmed by COVID-19. [15] [16] [17] [18] [19] [20] Hong Kong has experienced three small waves of COVID-19, which were well contained by public health measures. 21

We aimed to evaluate and characterize the scale and relationships of ED visits and excess mortality associated with the COVID-19 pandemic in Hong Kong that were not directly caused by SARS-CoV2. We compared the 2019 and 2020 (January through August) Hong Kong territory-wide ED visits, ED deaths, 28-day mortality rate, demographics and diagnostic groups in all 18 public EDs.

On the basis of previous studies, [15] [16] [17] [18] [19] we hypothesized that the COVID-19 pandemic would be associated with a decrease in ED visits and a higher 28-day non-COVID-19 mortality rate in 2020 compared with 2019.

We performed a territory-wide, retrospective, cohort study using data from an electronic administrative healthcare repositorythe Clinical Data Analysis and Reporting System (CDARS) 22which is managed by the Hospital Authority in Hong Kong. The Hospital Authority is the only public body overseeing all public hospitals and clinics in Hong Kong. CDARS retrieves territory-wide data from a centralized medical record system that is generated during the delivery of public healthcare services. This includes patients' demographics, ward movement, deaths, diagnoses, procedures, drug prescriptions, dispensing history and laboratory results taken from all attendees at public clinics and hospitals in Hong Kong. The data in this system is stored in different data centers in Hong Kong. The diagnostic coding is performed by physicians. The information technology team in each hospital will monitor the coding performance of each physician and issue J o u r n a l P r e -p r o o f serial reminders for coding each admitted patient if any missing code is found. It includes the inpatient and outpatient data of 80% of the 7.47 million population in Hong Kong 23, 24 , the remainder being in the private system.

Full-scale emergency medicine services providing 24-hour emergency physician-led care are only available in the EDs of 18 public hospitals. In 2019 the total number of attendees at these EDs was 2.2 million, equivalent to a total attendance rate of 290 per 1000 population. 25 We followed the STROBE 26 (Strengthening the reporting of observational studies in epidemiology) statement for reporting observational studies. The institutional review board of the University of Hong Kong/Hospital Authority West Cluster (UW 20-112) approved the study and granted waiver of participant consent.

China announced the outbreak of a novel viral pneumonia on 31 Dec 2020. The Hong Kong government launched its contingency plan within days after that although the first confirmed case was not identified until January 23 rd , 2020. All patients attending the EDs of the 18 public hospitals in Hong Kong between the pre-pandemic period of January 1 st , 2019 and August 31 st , 2019 (denoted as '2019') and between the pandemic period of January 1 st , 2020 and August 31 st , 2020 (denoted as '2020') were included. For year-to-year comparison, ED data recorded on February 29 th , 2020 was excluded from the analysis. Data extraction was undertaken on October 10 th , 2020, so all patients were followed-up for at least 28 days. We excluded hospital episodes with missing data for triage category and residential district, which represented a limited proportion of ED visits (1.04% in 2019 and 1.17% in 2020). As the epidemic and later pandemic evolved the implementation of active and enhanced surveillance was escalated. Hong Kong has rigorous testing systems and is likely to have recognized most of the confirmed cases upon hospitalization J o u r n a l P r e -p r o o f Data including sex, age, race, residential districts, arrival time, triage category (1-critical; 2emergency; 3-urgent; 4-semi-urgent; and 5-non-urgent), institutional residents, ambulance utilization, comprehensive social security assistance (CSSA) recipients, discharge destination (hospital admission, discharge, left without being seen, 27 certified dead in the ED), pandemic attendance period, and the diagnoses. The diagnoses included lower respiratory tract infection, airway disease, coronary heart disease, cerebrovascular disease, sepsis, trauma, cancer, diabetes mellitus, chronic kidney diseases, epilepsy, deliberate self-harm, mental disorders and poisoning.

Modification (ICD-9-CM) diagnosis codes recorded in each episode are listed in Table E1 .

Another set of diagnostic codes that are available in CDARS and used in public hospitals in Hong Kong is the Hospital Authority Master Disease Code Table ( HAMDCT). The HAMDCT extends the ICD-9-CM system with additional locally relevant terms and associated codes. A code number "519.8:8" was added to the HAMDCT indicating that COVID-19 was present.

The social deprivation index (SDI) for each residential district was calculated by taking the average of six selected variables from the census in 2016 in Hong Kong, namely unemployment, monthly household income < US$250, no schooling at all, one-person household, never-married status, and sub-tenancy. It was developed to measure the social disadvantage if each local urban area in Hong

Kong. The area with the highest values of this index was correlated with high standardized mortality rates and reduced access to hospital. The index has been adopted as a measure of the socioeconomic status of patients. 28

The primary outcome was all-cause mortality in the 28 days following an ED visit. '28-day mortality' covers all deaths, i.e., ED mortality, hospital mortality and out of hospital mortality up to 28-days. ED mortality was defined as any death certified in the ED (dead before arrival or dead after arrival). Hospital mortality was defined as any death occurring after admission to the hospital ward from the ED up to 28 days. Secondary outcomes were weekly number of ED visits and diagnosis-specific mortality.

Descriptive statistics were used to show the number of death, the distributions of baseline covariates and outcomes of ED visits in 2019 and 2020. A complete-case analysis was performed.

We adopted the standard population in Hong Kong (as estimated by the Census and Statistics Department) as the denominator in order to determine the 28-day annualized, age-adjusted estimate of excess mortality rate. 29 Age was divided into five-year age groups from 0 to 85 years old or above.

To minimize potential confounding biases due to discrepancy in baseline covariates of ED visits between years, we applied propensity score covariate adjustment to account for covariate imbalances for ED visits in 2019 and 2020. The propensity scores of all enrolled patients were calculated by using multivariable logistic regression adjusting for baseline variables with open causal pathway to death including sex, race, age group, residential region, EDs arrival time, wave period, ambulance utilization, institutional residents, CSSA recipients, SDI and triage category. In addition to linear terms of continuous variables, restricted cubic spline on continuous variables were used for propensity score estimation. The estimated propensity score represented the predicted probability of attending EDs before or after pandemic (ED visit in 2019 vs 2020) for each person given their covariates.

We compared study outcomes between the pandemic COVID-19 outbreak period in 2020 and the same pre-pandemic period in 2019 overall and by covariates as mentioned above. We calculated the percentage drops in ED visits from 2019 to 2020 in overall and by other covariates. Weekly ED visits during the different phases of the pandemic period in 2020 vis-á-vis corresponding period in 2019 were visualized in overall and by attendance characteristics and disease subgroups. Natural cubic splines with 95% confidence interval (CI) and equally spaced knots were fitted through the weekly ED visits by disease subgroup. We estimated adjusted odds ratios (OR) of COVID-19 effect in 2020 on 28-day mortality by multivariable logistic regression models adjusted propensity score as covariate. To assess heterogeneity of COVID-19 effects, we conducted repeated analyses considering subgroups based on weeks and different levels of covariates above. All the statistical analyses and figure generations were performed by using Stata version 16.0 (College Station, TX:

J o u r n a l P r e -p r o o f

A total of 1,035,562 ED visits occurred in the pandemic period (January 1 st to August 31 st , 2020) compared with 1,426,259 ED visits during the equivalent pre-pandemic period in 2019, a 27.4% reduction ( Table E2) . Table E4 provides the raw 28-day mortality count for respiratory condition in both years.

The reduction in ED visits (Table E2) The first inter-wave period was brief with no return to 2019 levels. The third wave period saw persistent reductions in ED visits except for cerebrovascular disease, cancer and Parkinson's Diseases that trended to 2019 levels. The major change was in deliberate self-harm that significantly increased. Figure 2 shows the dynamic changes in actual weekly count of certified deaths in the emergency departments. Apart from early January and a short period in late June there was a significant increase in overall EDs death certification between the cubic spline and weekly counts throughout the period. The dynamic changes, ebbs, and flows, in weekly count were similar in both prepandemic and pandemic periods.

J o u r n a l P r e -p r o o f For those patients admitted to the hospitals, counts and odds ratio for 28-day mortality were increased for lower respiratory tract infection, followed by diabetes, chronic kidney disease, and cerebrovascular disease. However, among patients who died in the ED, only one-third of the deaths were assigned diagnostics codes. Of these, over 97% were classified as 'cardiac arrest', 'instantaneous death', 'unattended death' or 'other unknown and unspecified cause of morbidity and mortality' ( Table E3 ) and less diagnostic groups were included with wide confidence intervals ( Figures E1-E2) . Trauma is the only group with an increased count and odds ratio for 28-day mortality in 2020. In Hong Kong, patients who died in the ED are reported to the coroners for investigations, including autopsy, subject to the application of waiver by the relatives. The autopsy report is not available in the hospital database.

There is limitations in this study. Firstly, this is a retrospective cohort study and may include inaccurate and incomplete documentation, as well as variance in the quality of the information recorded by physicians. However, in this territory-wide study all patients who registered for the ED service in the Hospital Authority were captured, the study findings are highly valid and reliable.

Secondly, the findings may not be generalizable beyond Hong Kong. Thirdly, the attendance data in 2019 should be interpreted with caution because of the large-scale social unrest that year.

Fourthly, our dataset only captures attendance records from the EDs of the 18 public hospitals in Hong Kong. Any information on healthcare services provided in the private sector is not accessible.

However, the private sector focuses on non-emergency care so the contribution to territory-wide mortality is likely to be low. Finally, it is difficult to objectively determine the degree of certainty of COVID-associated illness. However, during the pandemic all patients attending EDs who satisfied the clinical and epidemiological criteria for COVID-19 including all deaths were tested for SARS-CoV-2 by RT-PCR. Further, Hong Kong has robust testing processes which are equal to anywhere in the world. Thus, the degree of certainty is at least equal to any other clinically related COVID publication in the literature.

This study aimed to describe the change in ED visits and associated change of non-COVID-19 mortality during the early phase of the pandemic in Hong Kong. The reduction of ED visits in Hong Kong is compatible with observations in other countries and regions. 11, 30, 31 However, this is the first report on this phenomenon in a region with low COVID-19 incidence, where travelling within the territory was not restricted. The cumulative number of COVID-19 cases over time for Hong Kong, the United States, the United Kingdom and New Zealand are compared in Figure E3 .

Meanwhile, our study would confirm the notion that there was hospital avoidance during the pandemic 32 and also shows that there was a greater reduction of ED visits among women (-30.1%) compared with that among men (-24.5%) in our setting.

The greatest degree of reduction can be seen among children and adolescents (-60.1%). Otherwise the reduction across different age groups would be similar. We observed that patients with emergencies (critical, emergency and urgent categories) were less affected (-2.2% to -25.5%) than those categorized as semi-urgent and non-urgent (-29.5%). This suggests that critical and emergency patients in Hong Kong continued to attend EDs in usual numbers during the pandemic.

What is not clear is whether there were significant delays in ED visits and whether this was a factor impacting on increased mortality rates.

The degree of the reduction is not uniform among different clinical conditions and patient groups.

The authors analyzed the reduction from three different perspectives, namely respiratory diseases, general emergencies, and long-term medical conditions. ED visits for respiratory problems, namely lower respiratory tract infection, airway diseases (Chronic Obstructive Pulmonary Diseases and Asthma) and bronchitis fell rapidly from the beginning of 2020. The reduction J o u r n a l P r e -p r o o f continued throughout the study period and may be explained by the early adoption of precautionary measures in the community. 21, 33 The impact on emergencies was variable. There were small reductions among patients with cerebrovascular disease (stroke) and sepsis, but more pronounced changes among patients with coronary heart disease and trauma throughout the study period. The reductions in trauma and poisoning were more significant during the initial three months (waves 1 and 2), but returned to pre-pandemic levels by July 2020 when a local outbreak of COVID-19 started (wave 3). In Hong Kong the number of patient visits for deliberate self-harm was low but this rose from July 2020 despite a third wave.

Patients with chronic diseases (cancer, diabetes, chronic kidney diseases, epilepsy, dementia and

Parkinson's disease) demonstrated a similar degree of reduction in general. Changes were greatest during waves 1 and 2 and then returned towards pre-pandemic, seasonal variation levels after wave 2. The differences were less obvious among patients with cancer and chronic renal diseases, whose treatment continued as normal even though outpatient clinic and community nursing services were suspended during the period.

Early reports suggested that reductions in ED visits might lead to delayed disease presentation and treatment. 9 Studies from Hong Kong indicated that during the pandemic there were delays in presentation for both stroke 34 and coronary heart disease 35 that led to treatment delays and a deterioration in patient outcomes. In the current study, there was a significant increase in ED deaths (classified as out-of-hospital cardiac arrest) during 2020, which was not associated with SARS-CoV-2 infection.

In Hong Kong, EMS professionals are empowered by law to certify the death of a person if certain characteristics are identified, such as decapitation and transection, incineration, rigor mortis, decomposition and apnea in conjunction with destruction and/or functional separation from the body of the heart, brain, liver or lungs. The law and the practice did not changed throughout the pandemic.

The 28-day mortality rate in 2020 was higher than in 2019. It mainly affected patients aged 65 years or above, critical and emergency categories and those not living in residential home for elderly. The increase in out-of-hospital cardiac arrest in 2020 represents an increase in non-COVID-19 disease severity and mortality, and may be a result of delays in seeking medical care rather than the effect of fewer acute ED category attendances.

This study provides an overview on the early impact of COVID-19 on emergency care in Hong Kong. The data suggests increases in mortality in the ED and 28-day mortality among elderly patients and those with chronic medical conditions, possibly due to delayed presentations and hospital avoidance. While it is important to advise patients on social distancing measures, patients should be encouraged to seek medical advice if they have a significant illness. High quality telephone advisory centers could help to triage patients and advise on the appropriateness of attending an ED whilst maintaining early social distancing.

Our data suggests that the impact of the pandemic in different groups can be highly variable. The reasons underlying variable attitudes to ED visits during a pandemic should be investigated further using both quantitative and qualitative approaches. 

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We wish to dedicate this report to the patients we have described. We are also indebted to the many members of the frontline medical and nursing staff who demonstrated selfless and heroic devotion to duty in the face of this outbreak, both inside and outside hospitals, despite the potential threat to their own lives and those of their families.