A study in AJEM sets out to compare diagnostic accuracy between chest x-rays and lung ultrasound for diagnosing pneumonia. Other recent ED studies have consistently shown how lung ultrasound outperforms chest x-rays when diagnosing pneumonia.
The study compares diagnostic accuracy of lung ultrasound, performed by trained ED-ologists, versus chest x-rays in pneumonia patients.
All patients that were 18 years or older who were suspected to have acute pneumonia were included. Acute pneumonia was suspected if the patients had at least three of temperature ≥ 38℃, cough, dyspnea, heart rate > 100 bpm or saturated <92% on ambient air. Apart from normal standard of care pathway, including chest x-ray, these patients also underwent a lung ultrasound examination performed by ten ED physicians who all underwent a two day training programme in lung ultrasound.
The patient´s chests were scanned in eight sectors including visualising the back side of the lungs with the patient in a sitting position. Ultrasound diagnosis of pneumonia relied on either an ´alveolar´ or an ´interstitial´image.
The ´alveolar´ultrasound syndrome is the liver-like appearance of bronchograms whith the pleural line disrupted. It looks much like atelectasis apart from the bronchograms increasing in size with ventilation.
The ´interstitial´ ultrasound syndrome is a lot more meh… It is defined as the appearance of three or more B-lines, comet tails, resonance artefacts in a field of vision.
B-lines are the narrow based rays extending from the pleura all the way to the edge of the screen. B-lines is a a marker of fluid in the lungs and correlate with extravascular lung water. More comet tails means more water/loss of air.
The gold standard for diagnosing pneumonia would be chest CT. However, exposing all the study subjects to that radiation wouldn’t be justifiable. Instead the final end-point diagnosis, pneumonia or no pneumonia, was performed by a senior clinician who had access to the patients’ complete charts, clinical findings, x-rays, scans and ultrasound imaging.
144 patients fulfilled the inclusion criteriae. 123 of them had pneumonia. Overall 117/123, 95%, were correctly diagnosed using lung ultrasound. Chest x-rays could only identify 60%, 74 out of 123, of the pneumonias.
Lung ultrasound seems even more useful if one looks at patients with a short delay from onset of symptoms to presentation to ED. In patients presenting within 24h of onset of symptoms, lung US found 76% of the pneumonias compared to only 23% with x-rays.
Take home message
A clear win for lung ultrasound. Compares well with several recent studies telling us lung ultrasound outperforms chest x-rays for diagnosing pneumonia or other chest pathology. We could spare our patients from an awful lot of x-rays if we took ultrasound training seriously.
Study lives here:
Bourcier JE, Paquet J, Seinger M, Gallard E, Redonnet JP, Cheddadi F, Garnier D, Bourgeois JM, Geeraerts T.Performance comparison of lung ultrasound and chest x-ray for the diagnosis of pneumonia in the ED. Am J Emerg Med. 2014 Feb;32(2):115-8. doi: 10.1016/j.ajem.2013.10.003. Epub 2013 Oct 9.