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The Speed of Sound

The Speed of Sound

Diagnosing COVID-19 with Ultrasound

Butts, Christine MD

Emergency Medicine News: July 2021 - Volume 43 - Issue 7 - p 6
doi: 10.1097/01.EEM.0000758784.50714.88
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    COVID-19, ultrasound:
    Appearance of a normal lung on ultrasound. Note the A lines (arrowhead), which are artifacts created from reverberation of sound waves from the pleural line (arrow) through the air-filled lungs. Watch a video of this at http://bit.ly/VideosSound.
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    Figure

    When I first wrote about using ultrasound to diagnose COVID-19, testing wasn't readily available and a vaccine seemed pretty far off. A year on now, testing is better and more available, but still manages to miss some cases. I'm sure many of us have had the experience of seeing patients who seem to have a slam-dunk COVID diagnosis, only to have their tests come back negative. Some of these tests, however, are positive on the second or third attempt. Is there a better way to catch all of our COVID patients? Can ultrasound fill in the gaps in these cases?

    A recent study looked at this topic in an interesting way. (Ann Emerg Med. 2021;77[4]:385; https://bit.ly/33SUPcz.) They sought to integrate lung ultrasound into the overall clinical picture and to compare this with clinical evaluation alone and PCR testing. All patients presenting to the ED were assessed for possible COVID-19 infection with a basic evaluation (history, exam, etc.), and were classified by the evaluating physician as COVID likely or unlikely.

    All patients then had a lung ultrasound by the treating physician. The lung ultrasound plus the clinical scenario was assessed as being consistent with COVID-19 or not. All patients then underwent PCR testing for COVID. If it was positive, it was not repeated. If it was negative and there was significant clinical concern, the test was repeated within 72 hours. All patients also had follow-up at 30 days.

    Overall, the addition of ultrasound added considerable sensitivity to the clinical evaluation of these patients. Clinical suspicion alone had a sensitivity of 81% and specificity of 63% compared with clinical suspicion plus ultrasound, which had a sensitivity of 94% and a specificity of 95%.

    Downsides to this study? All of the ultrasounds were performed by experienced sonographers, and very ill patients (those requiring intubation) were excluded (although they did include those requiring noninvasive ventilation). They also used a fairly extensive scanning protocol, looking at six zones on each side.

    No hard and fast criteria were used for the diagnosis, but they looked for findings of interstitial syndrome (diffuse and bilateral B lines), particularly with areas of sparing or “skip lesions,” subpleural consolidations, and pleural thickening. (Read my columns on COVID-19 findings on lung ultrasound: EMN. 2020;42[6]:13; https://bit.ly/3dnCxDf; EMN. 2020;42[8]:14; https://bit.ly/2XqKXUK.)

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    Figure:
    Appearance of interstitial syndrome on ultrasound. Note the B lines (arrowhead) created by the presence of interstitial edema. As opposed to normal air-filled lungs, no A-lines or reverberation artifacts are seen extending from the pleural line (arrow). Watch a video of this at http://bit.ly/VideosSound.

    Does this study add to our clinical toolkit? I would say yes, particularly as COVID cases (hopefully) start to decrease. We will no doubt be dealing with this disease for a long time while trying to differentiate it from other causes of shortness of breath and fever. We know that our PCR testing is not always accurate, so adding ultrasound may help us recognize and isolate these patients earlier.

    Watch videos comparing a normal air-filled lung with one showing interstitial syndrome and COVID-19 pneumonia at http://bit.ly/VideosSound.

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    Dr. Buttsis the director of the division of emergency ultrasound and a clinical associate professor of emergency medicine at Louisiana State University at New Orleans. Follow her on Twitter@EMNSpeedofSound, and read her past columns athttp://bit.ly/EMN-SpeedofSound.

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