Clinical setting
St. Olav’s University Hospital is the local hospital in the city of Trondheim in central Norway, serving a population of approximately 300 000 inhabitants. Additionally, the hospital functions as a regional hospital in central Norway, covering more than 700 000 inhabitants. Annually, the university hospital manages more than 26 000 ED admissions in the main ED. As there is a separate ED for children, the patients managed in the main ED are primarily older than 16 years of age. The general rule is that patients must be referred to the ED by a physician, in most cases from their general practitioner (GP) or an urgent care center. The exception is situations when a patient’s condition requires emergency medical services (EMS). Therefore, the ED self-referral rate is low.
Study design
All patients presenting to the ED at St. Olav’s University Hospital with chest pain as their chief complaint during weeks 2–35 (January 6th to August 30th) in 2020 were included in this retrospective observational study. The most comprehensive preventive measures implemented by the government commenced from March 12th (week 11) and were gradually lifted approaching the summer. As the number of ED visits in 2020 seemingly normalized compared to the 2019 data following week 27, weeks 11–27 were considered well suited to study the initial effects of Covid-19 and the preventive measures implemented by the government. The analysis is therefore focused on this period. Corresponding data from weeks 2–35 in 2019 were utilized for comparison, providing an opportunity to interpret data in light of seasonal variations and the increasing rates of patient visits to the ED over the recent years.
RETTS triage system
All patients admitted to the ED go through an initial triage assessment, where they are assigned one out of five priority levels based on vital signs and algorithms specific for the patients’ chief complaint (emergency symptoms and signs, ESS). The Rapid Emergency Triage and Treatment System (RETTS ©, Predicare AB, Göteborg, Sweden) [12] is used both in-hospital and by the EMS. Based on this system, patients are primarily categorized as level 1 (red, highest acuity), level 2 (orange), level 3 (yellow) or level 4 (green, lowest acuity). Level 5 (blue) is used then patients present with other needs than emergency care.
Patient inclusion
All patients presenting with the chief complaint of chest pain according to the RETTS ESS #5 were included in the study (Fig. 1). This approach was chosen in order to include all patients presenting with chest pain to the ED, as opposed to defining the population on the basis of discharge diagnoses.
Data collection
Logistic data on patients referred to the ED were retrieved from Central Norway Regional Health Authority's IT (Hemit) department’s data warehouse. This included data from the local ED database (version 1.5.5. Copyright # Helse Vest IKT, Bergen, Norway). Using the administrative tool NIMES Vis (Nirvaco Medical Systems), supplementary data on the patients’ stay in hospital including discharge diagnoses and procedures were retrieved from the hospital’s patient and administration system (PAS, Hemit, 1986, version 5.2, Norway). All data were linked by an automated algorithm, anonymized, and stored on a safe hospital server.
Data on the total number of visits to the ED and the demographics of the population with regards to sex and age, was collected. The rate of patients transported to the ED by the EMS, the triage level, the in-hospital level of care, discharge diagnosis, in-hospital mortality, 30-day mortality, and the readmission rate within 30 days from the patients’ ED visit were included as surrogate markers of severity of the patents’ conditions. To account for the inconsistent reporting of how patients are transported to the ED (14.7% missing data), patients with a prehospital triage code were also included as being transported by the EMS. Regarding the remaining variables, 2.7% of patients had no recorded discharge diagnoses, 1.3% lacked data on possible readmissions and 30-day mortality, 1.0% of patients had no registered gender data and 0.3% lacked age information. These data are likely missing due to errors in the documentation process. However, the tools used for patient data collection in this study ensured a high level of accuracy to include the patients and match with their relevant clinical data. Therefore, there were generally very few missing data for the population. No data was missing for triage levels or level of care.
ICD-10 diagnosis and patient categorization
When discharged from the ED or hospital, all patients receive one or more ICD-10 code(s) reflecting their diagnosis [13]. Each patients’ primary ICD-10 code was used to classify patients into one of four predefined groups of diagnoses within the field of cardiology: (1) Non-specific chest pain (R07.4, R07.3, and R07.2), (2) ACS (unstable angina (I20.0) and acute myocardial infarction (I21)), (3) Arrhythmia (I47, I48, I49, and R00), and (4) Other cardiac conditions categorized based on the primary discharge diagnosis, including stable angina (I20.1-I20.9. I25, I30-35, I40-43, I50-51, Q21, Q23, Z95, D15, Z03.4, Z03.5, Z45.0, and Z94.1).
Statistics
Data were analyzed using STATA (STATA/IC 14.2, StataCorp, College Station, TX, USA). Results are reported as numbers with percentages, mean with standard deviations in normally distributed data and median with interquartile range in skewed data. The numbers of ED visits can vary substantially from day to day [6]. To reduce the impact of such periodic and random variation in the presented graphic figures, moving averages were utilized to enhance the underlying trends. Baseline 2019 data were depicted as five-week moving averages, while three-week moving averages were applied to 2020 data to capture more abrupt changes.