The medical community has learned much about the novel coronavirus in the past seven months, from risk factors for severe illness, treatments that could benefit hospitalized patients, and the effectiveness of masks and social distancing to prevent spread of the infection. Yet many questions remain, like why some patients with COVID-19 worsen several days after initially developing symptoms, in a pattern not characteristic of other viral illnesses.

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Clinicians who work in emergency departments must decide whether patients with COVID-19 are sick enough to require hospitalization or can safely recover at home. In the case of COVID-19, clinicians need better data upon which to base guidance and reassurance to patients who are sick but stable.

For this reason, our team studied COVID-19 patients who return to the hospital after an initial evaluation in the emergency department. We wanted to understand how often people need hospitalization after initially appearing well enough to recover at home, as well as when they develop worsening symptoms and which patients tend to require return visits. We analyzed the outcomes of 1,419 patients with COVID-19 who were evaluated and discharged from five UPHS hospital emergency departments from March through May.

Our results, published in Academic Emergency Medicine, have implications for systems seeking to monitor patients with CCOVID-19 as well as clinicians seeking evidence with which to counsel patients. Overall, nearly 5% of patients returned within 72 hours and needed admission to the hospital. For context, this rate may be 5-times higher than that described for all ED patients. An additional 3.5% of patients needed admission within 1 week. The fact that patients were hospitalized on their second visit indicates that their illness and symptoms progressed to the point where they needed a higher level of support, such as oxygen or therapeutic medications, than they could receive at home.

We also found that certain characteristics conferred higher risk for returning to the hospital. While it was not surprising that age was a risk factor, the increase in risk was dramatic: 9% of patients older than age 60 returned for hospital admission within 72 hours, more than three times the rate for patients aged 18 to 39. We found that patients with abnormal findings on chest x-ray, such as pneumonia, had double the probability of returning, as did patients who initially presented with fever and/or low oxygen levels (hypoxia). Obesity and high blood pressure (hypertension) were also risk factors for returning within 1 week.

These results do not suggest that emergency clinicians are making incorrect decisions in sending patients home—although caution is certainly warranted for patients with multiple risk factors. Instead, it suggests that an initial evaluation is simply a single snapshot in time for an evolving and somewhat unpredictable process.

Most patients will get better. Some need more help. And when they do need more help, we should ensure that they return for timely care, so that treatments are more effective. But how can we monitor patients outside the hospital without overwhelming the outpatient care system, particularly when the transition of patients from the emergency department is already fraught with challenges?

One solution is the COVID Watch system, developed at Penn Medicine. The program has enrolled thousands of patients—many of whom never require an emergency department visit. But for patients who are sent home from the ED, we can enroll patients in this text-message-based system to perform automated, daily check-ups, and advise patients to return should their symptoms worsen. A new study led by LDI Senior Fellows M. Kit Delgado, Krisda Chaiyachati, and Anna Morgan, and supported by the Patient-Centered Outcomes Research Institute (PCORI), will evaluate the effectiveness of this program as well as the additional use of pulse oximeters to monitor oxygen levels at home.

Caring for this entirely new illness requires clinicians and patients to navigate uncertainty. We have come a long way in the past 7 months. To continue to improve—and to help patients even when they are not in the hospital or clinic—we must improve our ability to communicate and coordinate care. This will require innovation and change on a population level, beyond our approach to individual patients.