Why is this interesting?

Digital radiology systems (PACS) allow point-of-care enhancement and adjustment of x-ray images. 'Inverted grayscale' viewing has been advocated as a way to improve the ability to detect small pneumothoraces on posterior-anterior chest x-rays (CXR).

This case-control cross-over study challenges this practice.

What did they do?

The researchers used CXRs of 106 adult patients with a known spontaneous pneumothorax and 162 matched-controls without pneumothorax, but who had presented with pneumothorax-consistent symptoms.

Using a senior radiologist as the gold standard diagnostician, two groups of five emergency physicians were then allocated to identify the presence of a pneumothorax in all 268 CXRs – one group using inverted grayscale and the other the conventional digital view.

To ensure the groups were comparable, the researchers also had each review a random selection of both inverted and conventional images, and compared how the group diagnostic sensitivities correlated.

Bottom-line:

Surprisingly, the sensitivity of pneumothorax detection was higher for conventional imaging than when using inverted grayscale (91.7% vs 84.5%). Specificity was comparable.

Be smart…

Although the researchers showed the inferiority of isolated inverted-grayscale imaging compared to conventional, it is a technique almost always used alongside first viewing a CXR with conventional contrast. Thus even if inferior, it is unlikely to undermine the diagnostic sensitivity of standard CXR reporting.

summary

• Ekrem Musalar, Salih Ekinci, Orkun Ünek, Eda Arş, Hakan Şevki Eren, Bengi Gürses, and Can Aktaş.
• Koç University Hospital, Emergency Department, Davutpaşa Caddesi No:4 34010 Topkapı, İstanbul, Turkey. Electronic address: emusalar@kuh.ku.edu.tr.
• Am J Emerg Med. 2017 Sep 1; 35 (9): 1217-1221.

IntroductionPneumothorax is a pathologic condition in which air is accumulated between the visceral and parietal pleura. After clinical suspicion, in order to diagnose the severity of the condition, imaging is necessary. By using the help of Picture Archiving and Communication Systems (PACS) direct conventional X-rays are converted to gray-scale and this has become a preferred method among many physicians.MethodsOur study design was a case-control study with cross-over design study. Posterior-anterior chest X-rays of patients were evaluated for pneumothorax by 10 expert physicians with at least 3years of experience and who have used inverted gray-scale posterior anterior chest X-ray for diagnosing pneumothorax.ResultsThe study included posterior anterior chest X-ray images of 268 patients of which 106 were diagnosed with spontaneous pneumothorax and 162 patients used as a control group. The sensitivity of Digital-conventional X-rays was found to be higher than that of inverted gray-scale images (95% CI (2,08-5,04), p<0,01). There was no statistically significant difference between the gold standard and digital-conventional images (95% CI (0,45-2,17), p=0,20), while the evaluations of the gray-scale images were found to be less sensitive for diagnosis (95% CI (3,16-5,67) p<0,01).ConclusionInverted gray-scale imaging is not a superior imaging modality over digital-conventional X-ray for the diagnosis of pneumothorax. Prospective studies should be performed where diagnostic potency of inverted gray-scale radiograms is tested against gold standard chest CT. Further research should compare inverted grayscale to lung ultrasound to assess them as alternatives prior to CT.Copyright © 2017 Elsevier Inc. All rights reserved.

This article appears in the collection: How useful is point-of-care ultrasound (POCUS) for diagnosing pneumothorax and other chest pathology?.

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