Distinguishing Admissions Specifically for COVID-19 From Incidental SARS-CoV-2 Admissions: National Retrospective Electronic Health Record Study

Abstract

Background Admissions are generally classified as COVID-19 hospitalizations if the patient has a positive SARS-CoV-2 polymerase chain reaction (PCR) test. However, because 35% of SARS-CoV-2 infections are asymptomatic, patients admitted for unrelated indications with an incidentally positive test could be misclassified as a COVID-19 hospitalization. Electronic health record (EHR)–based studies have been unable to distinguish between a hospitalization specifically for COVID-19 versus an incidental SARS-CoV-2 hospitalization. Although the need to improve classification of COVID-19 versus incidental SARS-CoV-2 is well understood, the magnitude of the problems has only been characterized in small, single-center studies. Furthermore, there have been no peer-reviewed studies evaluating methods for improving classification. Objective The aims of this study are to, first, quantify the frequency of incidental hospitalizations over the first 15 months of the pandemic in multiple hospital systems in the United States and, second, to apply electronic phenotyping techniques to automatically improve COVID-19 hospitalization classification. Methods From a retrospective EHR-based cohort in 4 US health care systems in Massachusetts, Pennsylvania, and Illinois, a random sample of 1123 SARS-CoV-2 PCR-positive patients hospitalized from March 2020 to August 2021 was manually chart-reviewed and classified as “admitted with COVID-19” (incidental) versus specifically admitted for COVID-19 (“for COVID-19”). EHR-based phenotyping was used to find feature sets to filter out incidental admissions. Results EHR-based phenotyped feature sets filtered out incidental admissions, which occurred in an average of 26% of hospitalizations (although this varied widely over time, from 0% to 75%). The top site-specific feature sets had 79%-99% specificity with 62%-75% sensitivity, while the best-performing across-site feature sets had 71%-94% specificity with 69%-81% sensitivity. Conclusions A large proportion of SARS-CoV-2 PCR-positive admissions were incidental. Straightforward EHR-based phenotypes differentiated admissions, which is important to assure accurate public health reporting and research.

An international observational study to assess the impact of the Omicron variant emergence on the clinical epidemiology of COVID-19 in hospitalised patients

“…One possible explanation for this finding would be if incidental SARS-CoV-2 infections, that is infections that were not the primary reason for hospitalisation, were more frequent during the Omicron period ; the high transmissibility of this variant, and the consequent peaks in numbers of infections, together with its reported association with lower severity, provides support for this hypothesis. However, in the subset of patients with data on the reason for hospitalisation there was no increase in the proportion of admissions thought to be incidental infections and indeed proportions in both study periods were consistent with frequencies of incidental infections in recent studies in the United States ( Klann et al, 2022 ) and the Netherlands ( Voor In ’t Holt et al, 2022 ), although in the latter, non-incidental infections included patients for whom COVID-19 was a contributing but not the main cause of hospitalisation. An alternative and less plausible explanation for the lower frequency of symptoms during the Omicron period would be that some of these patients developed symptoms other than those presented here, and which are severe enough to prompt hospital admission.…”

Incidence, risk and severity of SARS-CoV-2 reinfections in children and adolescents: a population-level study between March 2020 and July 2022

“…For example, hospitalization rates for children and adolescents with COVID-19 have been much higher in the US, 12,27 but many admissions might have been due to diseases other than COVID-19. 28 Many recorded pediatric COVID-19 deaths may also be due to other diseases. This may explain the spuriously higher rates of recorded COVID-19 deaths in USA compared with European countries, including Serbia.…”

Assessment of COVID-19 hospitalization risk during SARS-CoV-2 Omicron relative to Delta variant predominance, New York City, August 2021–January 2022

“…Thus, people hospitalized because of COVID-19 illness could not be distinguished from people hospitalized because SARS-CoV-2 infection exacerbated an underlying condition or because SARS-CoV-2 infection was an incidental diagnosis. 29 Incidental diagnoses were likely disproportionately common while Omicron predominated, given high infection prevalence. 30 COVID-19 hospitalizations were defined as NYC residents whose positive SARS-CoV-2 test was within 14 days before or 3 days after hospital admission.…”