What is your threshold for sensitivity of a test? If head CT missed 30% of bleeds, would we even do them? If UA’s missed 30% of UTI’s, would we even send them for anything other than culture? Would you feel comfortable making a decision based off a test that misses 30% of an infectious process that is common in your ED?
Here, 319 prospectively enrolled patients with suspected community acquired pneumonia were subjected to plain films and followed by Chest CT. CT revealed an infiltrate in a third of patients who did not have an infiltrate on chest film and excluded CAP in 29.8% of patients with an infiltrate on chest film. 6.9% of patients were hospitalized (rather than discharged), and 7.2% were discharged rather than admitted based off CT findings (22 vs 23 patients).
The authors suggest that changing the disposition on 14% of patients is worth the “just scan ’em” mentality, while I would argue that a better question would be, why waste everyone’s time when you could just pull out the ultrasound? (Not to mention you would have an answer faster, at ~95% sensitivity?)