Outpatient Lung Ultrasound Findings in COVID May Not Help With Risk Stratification

coronavirus infection in lungs, COVID-19
Researchers investigated the prevalence, natural history, and clinical significance of pulmonary disease in outpatients with SARS-CoV-2.

A new study suggests that although there is a high prevalence of lung ultrasound (LUS) findings in outpatients positive for SARS-CoV-2 infection, most of these patients show an improvement or resolution of these findings after 1 to 2 weeks, suggesting LUS may not be an appropriate risk stratification tool in outpatients with COVID-19. Findings from this study were published in BMJ Open Respiratory Research.

In the prospective cohort study, researchers from Stanford assessed LUS findings from 102 outpatients positive for SARS-CoV-2 (mean age, 43.6 years; 52% female) to identify interstitial pneumonia. A total of 14 healthy controls (mean age, 43.8 years; 71% female) were also enrolled and underwent LUS examinations at baseline.

Videos of LUS were randomized and scored by 2 independent sonographers. The severity of B-lines, pleural irregularity, and consolidations were determined for each of the 6 lung zones for each patient.

The highest feature score from each of the 6 lung zones were added together to determine an overall severity score that ranged from 0 (normal) to 18 (most severe). In the study, patients were classified as having a positive LUS if their severity scores were more than 0, while those with a negative LUS had severity scores equal to 0.

Out of 158 LUS examinations performed, 102 were performed at baseline and 42 were performed over follow-up.  The median duration between testing positive for COVID-19 and baseline LUS was 6.8 days. At baseline, the LUS severity scores ranged from 0 to 14. Among patients with COVID-19, approximately 41% (n=42) were LUS-positive, while 59% (n=60) were LUS-negative. All 14 healthy controls were LUS-negative.

In an analysis that compared patients who were COVID-19-positive/LUS-positive with those who were COVID-19-positive/LUS-negative, those who were LUS-positive had a significantly higher mean age (47.4 years vs 41.0 years; P =.038), were more often female vs male (67% vs 33%, respectively; P =.022), and had a lower body mass index (25.2 vs 27.8; P =.009).

At the 1-week follow-up period, 37% (n=9) of patients who were COVID-19 positive and LUS-positive worsened and 63% (n=15) improved. Persistent symptoms of cough and/or shortness of breath were more frequently reported at 1 week in patients who worsened (67% vs 27%; P =.067). While LUS findings improved in the majority of patients by 1 or 2 weeks from the baseline LUS, some patients continued to have persistent LUS severity scores of more than 2.

At 8 weeks, only 1 patient who responded to the follow-up survey was hospitalized for fever and shortness of breath. These events occurred 2 days following the baseline examination in the patient who had a severity score of 6. None of the patients in the study died or required mechanical ventilation over the 8-week follow-up period.

A limitation of the study was the lack of data regarding the date of infection and its association with baseline LUS examinations. According to the researchers, the heterogeneity in the duration between infection and LUS exams “could theoretically lead to LUS findings resolving by the time of baseline examination, or LUS findings developing after baseline examination.”

In terms of LUS, the researchers conclude that their findings suggest “limited utility of this technique for risk stratification and surveillance in the outpatient setting.”


Fairchild RM, Horomanski A, Mar DA, et al. Prevalence and significance of pulmonary disease on lung ultrasonography in outpatients with SARS-CoV-2 infection. BMJ Open Respir Res. 2021;8(1):e000947. doi:10.1136/bmjresp-2021-000947