Health system and electronic health records
Healthcare is provided by both the public and private sector in Singapore. The public sector covers about 80% of tertiary acute care but the converse is true for primary care, of which about 80% is covered by the private sector [24]. SingHealth, the largest of three public healthcare clusters in Singapore, is a network of acute hospitals, national specialty centres, subacute hospitals, and primary care polyclinics [25]. At the beginning of the COVID-19 pandemic, SingHealth institutions included four acute hospitals (Singapore General Hospital (SGH, 1796 beds), Changi General Hospital (CGH, 1071 beds), Sengkang General Hospital (SKH, 799 beds), and KK Women’s and Children’s Hospital (KKH, 848 beds)), five specialty centres (the National Cancer Centre Singapore (NCCS), National Heart Centre Singapore (NHCS), Singapore National Eye Centre (SNEC), National Dental Centre Singapore (NDCS), and National Neurosciences Institute (NNI)), three subacute hospitals (Sengkang Community Hospital (233-beds), Outram Community Hospital (99 beds) and Bright Vision Hospital (276 beds)), and eight of 23 polyclinics in the country providing primary care under the public sector [26].
SingHealth uses a comprehensive electronic medical records (EMR) system across all the care settings. In Singapore, information technology for the public healthcare sector is centrally managed by Synapxe (formerly, the Integrated Health Information Systems, IHiS). Synapxe also administers the SingHealth-Synapxe Electronic Health Intelligence System (eHints), an enterprise data repository that integrates information from multiple healthcare transactional systems including clinical, administrative and ancillary systems within SingHealth to serve analysis and reporting functions for operational and clinical purposes [27].
COVID-19 registry governance
The COVID-19 registry was developed through a collaborative effort among infectious disease clinicians and epidemiologists from the Department of Infection Prevention and Epidemiology (DIPE, SGH), health services researchers from the Health Services Research Centre (SingHealth), and data system experts from Synapxe (referred hereafter as the core development team). The SingHealth disease registry policy provided the framework for registry development and governance. The COVID-19 registry is governed by a steering committee with representatives from every SingHealth institution that received COVID-19 patients. Registry data can be accessed according to SingHealth’s disease registry data use policy after approval from the steering committee. Data requests for research are required to have prior ethics approval. Informed patient consent was not required as per the SingHealth disease registry policy.
COVID-19 registry data integration
The COVID-19 Registry is fronted by a dashboard which displays variables linked from other subject areas in eHIntS using patient identifiers (National Registration Identity Card (NRIC) number and/or case number, which are unique to each individual and visit, respectively) (see “COVID-19 registry development”). There was no manual data entry specifically for the registry.
COVID-19 diagnostics and case patient identification
Suspect case criteria defined by the Ministry of Health, Singapore (MOH) for the novel respiratory infection on January 21, 2020 was (a) a person with clinical signs and symptoms suggestive of pneumonia or severe respiratory infection with breathlessness AND travel to mainland China within last 14 days; or (b) a person with an acute respiratory illness of any degree of severity who, within 14 days before onset of illness, had been to a hospital in mainland China or had close contact with a case of 2019 novel coronavirus infection [28]. As the pandemic evolved rapidly, individual institutions modified case definitions and clinical workflows according to the epidemiological situation [29]. All hospitals maintained a manual listing of suspected and confirmed cases for reporting and contact tracing purposes.
In-house laboratory PCR testing for this novel coronavirus was available at SGH on January 23, 2020, the same day that the first patient with laboratory-confirmed COVID-19 was identified. Between January 2020 and April 15, 2020, the COVID-19 registry included all patients meeting institutional/national epidemiological case definitions regardless of laboratory test results, as testing was limited by laboratory testing capacity. Between April 15, 2020 and October 9, 2021, SARS-CoV-2 PCR test was widely accessible and subsidized and hence was utilized for all suspected cases and for active surveillance amongst high-risk persons such as healthcare workers and dormitory residents [30]. Only laboratory-confirmed SARS-CoV-2 PCR-positive patients were included in the COVID-19 registry during this period.
As of October 8, 2021, 84.7% of Singapore’s population had completed their COVID-19 vaccination [31]. Full vaccination was found to reduce the risk of severe COVID-19 and death by ten-fold (0.12% versus 1.59% respectively) [30]. At this stage, national COVID-19 control measures transitioned from containment to mitigation. COVID-19 diagnosis and surveillance testing changed from a primarily PCR-based test to an Antigen Rapid Test (ART) based method from October 10, 2021 [32]. As this included ART self-tests, the COVID-19 registry incorporated national electronic COVID-19 tagging for case patient identification between October 10, 2021 and May 8, 2022.
Electronic patient tagging
Several COVID-19-related electronic tags were introduced throughout the pandemic. These tags managed centrally at a national level, appeared as alerts on the individual patient health record. The first group of tags were for persons issued the Quarantine Order (QO) and Stay Home Notice (SHN) following return from international travel. The second tag was introduced to identify patients who were COVID positive, either through ART self-test, ART at a primary care facility that declared their COVID-19 status in a centrally managed COVID-19 portal, or a laboratory-based SARS-CoV-2 PCR test, between October 10, 2021 and May 8, 2022. The second electronic tag was utilized to identify COVID-19 cases for the COVID-19 registry. From May 9, 2022, identification of COVID-19 patients for the COVID-19 registry reverted to laboratory-confirmed cases through PCR and/or ART within SingHealth institutions.
COVID-19 registry development
Phase 1: Information needs assessment
The core development team performed information needs assessment through internal discussions and engagement with clinicians who had COVID-19-related research questions and identified eight general areas to be included in the registry. These areas broadly included population-level transmission dynamics and clinical disease characteristics and their modifiers (Table 1).
Phase 2: Identification of data elements
Next, the team identified the data elements for each of the areas determined in phase 1. A variety of resources including scientific and media publications related to COVID-19, expert opinions, COVID-19 specific data collection tools, national health information system (e.g. COVID-19 tag from national database), hospital electronic health record system and the eHints data dictionary were consulted (Table 2).
Phase 3: Selection of a minimum data set (MDS) and data types
The minimum data set (MDS) is a defined set of data variables in a health information system (in this case, eHints) containing the variables essential for meeting the needs of most users in our healthcare system. By precisely defining data elements, the MDS serves as a data dictionary that promotes transparency and clarity in data collection, analysis, and reporting.
As the COVID-19 pandemic progressed, clinical workflows became protocolized and new templates with variables relevant to bed allocation (such as admission to dedicated respiratory surveillance wards for COVID-19 suspect patients or COVID-19 isolation wards for COVID-19 confirmed patients) and management were collected electronically and became available in eHints. These were later added to the MDS.
Two clinicians from the study team mapped the International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) and Systematized Nomenclature of Medicine Clinical Terms (SNOMED) codes to the specific comorbidities and complications in order to build the comorbidities and complications database. Algorithms were created by combining diagnostic codes and other structured clinical data to define comorbidities and COVID-19 complications in eHints. Pre-existing conditions prior to COVID-19 diagnosis were considered to be comorbidities and conditions that developed following COVID-19 diagnosis were considered complications. As COVID-19 emerged as a novel disease, literature reviews were conducted regularly in order to better understand the disease characteristics and to incorporate more appropriate symptoms and conditions in the registry database.
Specific subject areas and variables relevant to the identified data elements were selected from eHints. Three types of data utilized by the registry are (1) structured data such as demographics, visit details, ICD-10-CM diagnostic codes and COVID-19 electronic tags, (2) unstructured data such as discharge summaries and radiology reports, and (3) specific comorbidities and COVID-19 complications coded from raw data such as ICD diagnostic and SNOMED codes.
Phase 4: Validation of data variables
All data variables in the COVID-19 registry were included in the internal validation process – demographics, laboratory results, vital signs, in-hospital patient movement, comorbidities and complications, therapeutics, vaccinations and outcome measures, to ensure that the data linked in eHints were correct.Ten percent of all patients with at least one variable, from each institution in the registry were sampled. The gold standard reference was manual review of the EMR for each of the nineteen comorbidities and fourteen complications.
Phase 5: Evaluation and modification of MDS
Throughout the COVID-19 pandemic, MDS was modified to align with evolving information and public health and clinical measures such as the introduction of electronic tagging systems, incorporation of therapeutics, and implementation of vaccination strategies.
Ethics
SingHealth Centralized Institutional Review Board (CIRB Ref: 2021/2027) determined that ethical deliberation was not required for the project as data from the registry would be de-identified prior to analysis for research. All methods were performed in accordance with the relevant SingHealth disease registry guidelines and regulations.