Impact of changing case definitions for coronavirus disease 2019 (COVID-19) hospitalization on pandemic metrics

Abstract

Objective: To examine the impact of commonly used case definitions for coronavirus disease 2019 (COVID-19) hospitalizations on case counts and outcomes. Design, patients, and setting: Retrospective analysis of all adults hospitalized between March 1, 2020, and March 1, 2022, at 5 Massachusetts acute-care hospitals. Interventions: We applied 6 commonly used definitions of COVID-19 hospitalization: positive severe acute respiratory coronavirus virus 2 (SARS-CoV-2) polymerase chain reaction (PCR) assay within 14 days of admission, PCR plus dexamethasone administration, PCR plus remdesivir, PCR plus hypoxemia, institutional COVID-19 flag, or COVID-19 International Classification of Disease, Tenth Revision (ICD-10) codes. Outcomes included case counts and in-hospital mortality. Overall, 100 PCR-positive cases were reviewed to determine each definition’s accuracy for distinguishing primary or contributing versus incidental COVID-19 hospitalizations. Results: Of 306,387 hospital encounters, 15,436 (5.0%) met the PCR-based definition. COVID-19 hospitalization counts varied substantially between definitions: 4,628 (1.5% of all encounters) for PCR plus dexamethasone, 5,757 (1.9%) for PCR plus remdesivir, 11,801 (3.9%) for PCR plus hypoxemia, 15,673 (5.1%) for institutional flags, and 15,868 (5.2%) for ICD-10 codes. Definitions requiring dexamethasone, hypoxemia, or remdesivir selected sicker patients compared to PCR alone (mortality rates 12.2%, 10.7%, and 8.8% vs 8.3%, respectively). Definitions requiring PCR plus remdesivir or dexamethasone did not detect a reduction in in-hospital mortality associated with the SARS-CoV-2 Omicron variant. ICD-10 codes had the highest sensitivity (98.4%) but low specificity (39.5%) for distinguishing primary or contributing versus incidental COVID-19 hospitalizations. PCR plus dexamethasone had the highest specificity (92.1%) but low sensitivity (35.5%). Conclusions: Commonly used definitions for COVID-19 hospitalizations generate variable case counts and outcomes and differentiate poorly between primary or contributing versus incidental COVID-19 hospitalizations. Surveillance definitions that better capture and delineate COVID-19–associated hospitalizations are needed.

Use of Electronic Clinical Data to Track Incidence and Mortality for SARS-CoV-2–Associated Sepsis

“…In hospital systems with widespread use of SARS-CoV-2 testing for all inpatients, such as MGB, PPV may be lower than in systems that perform more targeted testing because the chance of diagnosing incidental or noncontributing SARS-CoV-2 infections rises with increased testing . Third, we may have misattributed organ dysfunction to SARS-CoV-2, particularly during periods of high community transmission when some hospitalized patients tested positive for SARS-CoV-2 while hospitalized for other reasons . Fourth, our analyses of mortality trends for presumed bacterial sepsis may have been confounded by changes in case mix for the non–COVID-19 population over time.…”

“… 46 Third, we may have misattributed organ dysfunction to SARS-CoV-2, particularly during periods of high community transmission when some hospitalized patients tested positive for SARS-CoV-2 while hospitalized for other reasons. 22 Fourth, our analyses of mortality trends for presumed bacterial sepsis may have been confounded by changes in case mix for the non–COVID-19 population over time. We did adjust our estimates for patient demographics and comorbidities, but we did not adjust for vital signs or laboratory measures, allowing for the possibility of residual confounding.…”

“…We defined COVID-19 hospitalizations as any encounter with a positive SARS-CoV-2 polymerase chain reaction (PCR) within 3 days before or during admission, or by the presence of an institutional COVID-19 EHR flag (triggered by positive PCR results, including from outside the MGB system) overlapping with the admission and present for 5 or more calendar days, including posthospitalization days if discharge or death occurred before 5 days. 22 Encounters from patients with a positive PCR or flag start date between 31 to 90 days prior to admission were excluded from the COVID-19 hospitalization definition to minimize patients with persistently positive PCR results following resolved infections.…”

Are Patients With an International Classification of Diseases, 10th Edition Discharge Diagnosis Code for Sepsis Different in Regard to Demographics and Outcome Variables When Comparing Those With Sepsis Only to Those Also Diagnosed With COVID-19 or Those With a COVID-19 Diagnosis Alone?

“…This disconnect has also been demonstrated in COVID-19 patients. Using chart review, the study by Shappell et al ( 23 ) found that a COVID-19 ICD-10 discharge diagnostic code had only a fair positive predictive value (74%) for an acute COVID-19 infection as the primary or secondary reason for admission. Similarly, we found that patients with sepsis ICD-10 code + COVID-19 diagnosis had lower systolic blood pressure, higher initial lactate level, increased ICU admission, and higher baseline disease severity (GCS, MEWS scores) when compared to COVID-19 diagnosis-only patients.…”

Differentiating patients admitted primarily due to coronavirus disease 2019 (COVID-19) from those admitted with incidentally detected severe acute respiratory syndrome corona-virus type 2 (SARS-CoV-2) at hospital admission: A cohort analysis of German hospital records

“… 3 , 8 , 9 Nonetheless, the prevailing definitions used to determine severity level of COVID-19 hospitalizations have led to invalid case counts and outcomes. 10 …”