Article Notes
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.
Daniel Jolley