The Clinical Course of Coronavirus Disease 2019 in a US Hospital System

A Multistate Analysis

Aaloke Mody; Patrick G. Lyons; Cristina Vazquez Guillamet; Andrew Michelson; Sean Yu; Angella Sandra Namwase; Pratik Sinha; William G. Powderly; Keith Woeltje; Elvin H. Geng


Am J Epidemiol. 2021;190(4):539-552. 

In This Article

Abstract and Introduction


There are limited data on longitudinal outcomes for coronavirus disease 2019 (COVID-19) hospitalizations that account for transitions between clinical states over time. Using electronic health record data from a hospital network in the St. Louis, Missouri, region, we performed multistate analyses to examine longitudinal transitions and outcomes among hospitalized adults with laboratory-confirmed COVID-19 with respect to 15 mutually exclusive clinical states. Between March 15 and July 25, 2020, a total of 1,577 patients in the network were hospitalized with COVID-19 (49.9% male; median age, 63 years (interquartile range, 50–75); 58.8% Black). Overall, 34.1% (95% confidence interval (CI): 26.4, 41.8) had an intensive care unit admission and 12.3% (95% CI: 8.5, 16.1) received invasive mechanical ventilation (IMV). The risk of decompensation peaked immediately after admission; discharges peaked around days 3–5, and deaths plateaued between days 7 and 16. At 28 days, 12.6% (95% CI: 9.6, 15.6) of patients had died (4.2% (95% CI: 3.2, 5.2) had received IMV) and 80.8% (95% CI: 75.4, 86.1) had been discharged. Among those receiving IMV, 35.1% (95% CI: 28.2, 42.0) remained intubated after 14 days; after 28 days, 37.6% (95% CI: 30.4, 44.7) had died and only 37.7% (95% CI: 30.6, 44.7) had been discharged. Multistate methods offer granular characterizations of the clinical course of COVID-19 and provide essential information for guiding both clinical decision-making and public health planning.


A careful characterization of the clinical course of coronavirus disease 2019 (COVID-19) during hospitalization will offer important insights into patients' prognosis and the anticipated burden and duration of resources required for their care—basic clinical information which is still coming into focus for this novel pathogen. Hospitalized patients may take numerous pathways: Some only require brief stays, while others deteriorate and require admission to the intensive care unit (ICU), with or without invasive mechanical ventilation (IMV).[1–6] Even if these patients survive, many will experience protracted hospital courses prior to discharge. Deaths could occur immediately after admission or after decompensations later on in the hospitalization. An understanding of how patients transition through multiple clinical states over the course of their hospitalization—and the timing of these transitions—will offer situational awareness and information for clinical decision-making and public health planning as the epidemic continues to evolve.

To date, published data on the hospital course of COVID-19 do not yet provide a comprehensive descriptive picture indicative of the experience in the United States. For example, while case series do describe the number or incidence of deaths,[1–6] such analyses have not captured information on movement between multiple clinical states over the course of hospitalization. Additionally, the rapidly evolving nature of the pandemic means that in many reports a substantial proportion of patients are still in the midst of their illness.[7] These analyses have either presented cross-sectional estimates that do not account for this unequal follow-up time or have excluded patients with incomplete follow-up time, potentially creating bias in both scenarios.[1–9] Furthermore, much of the early data on hospitalizations focused only on critically ill patients and came from single-center studies conducted earlier in the epidemic, largely from the worst-hit areas such as Wuhan, China,[1–3] Lombardy, Italy,[4] and New York, New York,[5,6] where outcomes may not be representative of outcomes elsewhere. Thus, more rigorous data from regions where the burden of COVID-19 did not exceed the capacity of health-care systems is needed to inform COVID-19 planning in the United States going forward.

To address these needs, we used data from the BJC HealthCare Hospital system in St. Louis, Missouri, and the surrounding regions to examine the totality of experience across a number of clinical conditions (e.g., inpatient floor admission, ICU stay, death, discharge) in a cohort of patients who were admitted with COVID-19. We used multistate methods to estimate the proportion of patients in various clinical conditions over time, as well as the amount of time spent in each state and rates of transition from each state. This analytical technique permits a more comprehensive examination of the cascade of outcomes[10] during COVID-19 hospitalizations for informing planning and policy.