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Independent Correlates of Hospitalization in 2040 Patients with COVID-19 at a Large Hospital System in Michigan, United States


Prognostic information about the novel coronavirus disease (COVID-19) pandemic is important for patient care. While China reported prediction models on length of stay and mortality1 and US data is emerging, predictors for hospitalization have not been well defined yet.2, 3 Our study aims to identify correlates for hospitalization in a large cohort of COVID-19 patients in Michigan.


We performed a retrospective review of patients diagnosed with SARS-CoV2 infection by a positive RT-PCR on nasopharyngeal swab from the largest healthcare system in Southeast Michigan (8 hospitals), through April 1, 2020. We abstracted demographics, comorbidities, medications, and calculated disease burden with the Charlson Comorbidity Index (CCI).4 Logistic regression evaluated associations and multivariate analyses, including variables with p value <0.20 on univariate analysis (SPSS).


Of 2040 COVID-19 positive patients, 1305 (64.0%) were hospitalized and 735 (36.0%) were evaluated in the Emergency Department (ED), discharged home, and did not require reevaluation within 14 days.

Univariate correlates of hospitalization included:: Age > 60 (OR:3.4, 95% CI: 2.8–4.1), male (OR:1.4, 95% CI: 1.2–1.7), Caucasian (OR:1.4, 95% CI: 1.0–2.0), obesity (OR:1.5, 95% CI: 1.2–1.9), CCI > 2 (OR:5.2, 95% CI: 4.2–6.5), ACE-I/ARB use (OR:2.4, 95% CI: 2.0–2.9), tachycardia (heart rate > 100 beats/min) (OR:1.6, 95% CI: 1.3–1.9), tachypnea (respiratory rate > 20 breaths/min, OR:5.3, 95% CI: 4.0–7.1), and hypoxia (oxygen saturation < 90%, OR:21.7, 95% CI: 8.0–59.1, Table 1).

Independent correlates of hospitalization included: Age > 60 (aOR:2.1, 95% CI: 1.4–3.1), CCI > 2 (aOR:3.2, 95% CI: 2.1–4.8), male (aOR:1.9, 95% CI: 1.5–2.5), obesity (aOR:1.8, 95% CI: 1.4–2.4), ACE-I/ARB use (aOR:1.5, 95% CI: 1.1–2.0), tachycardia (aOR:1.5, 95% CI: 1.1–2.0), tachypnea (aOR:2.9, 95% CI: 2.1–4.1), and hypoxia (aOR:15.0, 95% CI: 4.7–48.0, Table 1).


We found that older age (>60 years), obesity, CCl > 2, ACE-I/ARB use, and male sex as independent correlates for hospitalization in COVID-19 patients, after controlling for objective clinical findings of illness severity of tachycardia, tachypnea, and hypoxia. Older age and higher comorbidity burden have also been reported as risk factors for mortality in hospitalized COVID-19 patients.2, 5, 6 This information can provide insight to help guide triage decisions of COVID-19 patients in the emergency center and help appropriate allocation of healthcare resources in the time of a pandemic. The main limitations of our study include its retrospective nature, limited follow-up time, and potential inaccuracies in the medical records. Additionally, the high admission rate in our cohort suggests high patient acuity hence limiting the utility of the identified correlates in other settings such as outpatient offices.


Older age, medical comorbidities, obesity, ACE-I/ARB use, and male sex are independent correlates of hospitalization in COVID-19 patients presenting to the emergency department.

Table 1 Univariate and multivariate analyses of demographic, comorbidity and clinical indices among hospitalized and outpatient cohorts


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A.H. was involved with the development and implementation of the study design and methods and revised the manuscript. All authors were involved with manuscript preparation, multiple draft revisions, conception of tables and have reviewed and approved the manuscript for submission.

A.H., F.O. and Z.I. had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

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Correspondence to Zaid Imam.

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Conflict of Interest

The inpatient cohort reported in this manuscript has been evaluated by our research group for mortality correlates separately in another study that is currently accepted for publication. The outpatient cohort is part of a larger cohort that was analyzed in a separate study currently submitted for publication. Neither of these studies evaluated the outcomes reported in this study or compared the two cohorts of patients.

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Imam, Z., Odish, F., Armstrong, J. et al. Independent Correlates of Hospitalization in 2040 Patients with COVID-19 at a Large Hospital System in Michigan, United States. J GEN INTERN MED 35, 2516–2517 (2020).

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Key Words

  • COVID-19
  • hospitalization
  • epidemiology
  • risk factors