Lung Ultrasound Beats Chest X-Ray for COVID-19 Diagnosis

Ingrid Hein

November 06, 2020

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

Point-of-care lung ultrasound is better than chest x-ray for diagnosis of COVID-19 pneumonia, according to new research.

"We continue to be confronted with a diagnostic challenge — patients often have vague non-specific multi-system presentations," Kendra Mendez, MD, Temple University Hospital, Philadelphia, Pennsylvania, said in her presentation at the American College of Emergency Physicians (ACEP) 2020 "Unconventional" online congress. Researchers from her center set out to compare portable modalities to diagnose COVID-19.

"Lung ultrasound sensitivity outperforms chest x-ray," Mendez confirmed.

Investigators compared the diagnostic performance of lung ultrasound (LUS) performed with a portable hand-held device with chest x-ray (CXR) in patients at high-risk for COVID-19. For a definitive diagnosis, COVID-19 infection was confirmed with noncontrast-enhanced computed tomography (NCCT), "the diagnostic standard," Mendez said, delivering "near-perfect sensitivity of atypical pneumonia radiographically."

The prospective study was performed over a 2-week period in April 2020 during a surge in COVID-19 cases at Temple University Hospital. A total of 143 patients age 18 and over with signs and symptoms of COVID-19 were enrolled as they came into the emergency department. To enroll, patients had to present with a temperature of 100.4° Fahrenheit (38° Celsius) or higher, a heart rate of 100 bpm or higher, a respiratory rate of 16 rpm or greater, SpO2 less than 94%, and presentation of a combination of cough, dyspnea, myalgia, malaise, ageusia, and anosmia.

"Pregnant patients and those unable to consent were excluded," Mendez noted.

In addition, medical residents or an emergency physician performed an LUS using a portable device, followed by a portable anterior-posterior CXR on all participants.

NCCT Confirmed Cases

In the 70 patients with both positive LUS and CXR test results, 58 had a positive NCCT.

In the 42 patients with a positive LUS and a negative CXR, only 23 had a positive NCCT.

In the six patients who had a positive CXR and a negative LUS, there were no positive NCCTs, indicating lung ultrasound was the more reliable indicator.

Researchers performed an NCCT on seven of the 25 remaining patients who had negative LUS and CXR, because they presented with high-risk symptoms including lymphopenia less than 1000/mm3, a temperature higher than 101° Fahrenheit, a heart rate equal to or higher than 110 bpm, a respiratory rate of 20 or more, oxygen levels lower than 92%, systolic blood pressure lower than 100 mmHg, and were considered immunocompromised.

Two out of these seven patients had a positive NCCT result.

"Both had similarly poor specificities," Mendez reported in her talk.

She reported that LUS had a sensitivity of 97.6% (95% confidence interval [CI], 91.6 - 99.7) compared with CXR at 69.9% (95% CI, 58.8 - 79.5). Specificity was 33.3% (95% CI, 16.5 - 54.0) for LUS and 44.4% (95% CI, 25.5 - 64.7) for CXR.

A total of 143 patients were enrolled; 27 were considered low risk by the attending emergency physician and six were admitted for alternative diagnoses without advanced imaging, leaving a study population of 110 patients. Of those, 81 tested positive for COVID-19 with NCCT, with a disease prevalence of 75%.

"This study supports portable bedside ultrasound in addition to chest x-ray as a possible screening modality for patients with suspected COVID-19 pneumonia," Bret Nicks, MD, Wake Forest University, Winston-Salem, North Carolina, who was not involved in the study, told Medscape Medical News in an email interview. This will help determine a diagnosis, he said, as "patients presenting to the emergency department with COVID-19 can have a broad constellation of signs and symptoms."

Mendez added that LUS can be an especially valuable triage screening modality in resource-limited settings.

American College of Emergency Physicians (ACEP) 2020. Abstract #6. Presented Tuesday October 27, 2020.

Nicks and Mendez have disclosed no relevant financial relationships.

Ingrid Hein is a freelance health and technology reporter based in Hudson, Quebec.

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