This isn’t the first go ‘round for these authors. In 2013, they published their first attempt – which demonstrated a sensitivity of 98.8% for thoracic injury, but a specificity of 13.3%. The rule was, essentially, minimal improvement over clinical judgement and reliably decrease resource utilization.
In another massive effort, these authors enrolled 11,477 patients in 8 trauma centers – 6,002 in the derivation phase and 5,475 in the validation phase. Based on their prior work, they evaluated each for the presence of 14 potentially predictive features. Following data collection for the derivation phase, recursive partitioning was used to develop two decision instruments: one for “major” injuries requiring intervention, and one for “major and minor” injuries requiring a minimum of observation.
Their new criteria, comprised of about half of the 14 tested, were much improved over the prior study. In the validation phase, the “major and minor” decision instrument had sensitivity of 99.2% for major injuries and 95.4% for major or minor injury. Specificity was still poor at 25.5%, but improved from the prior study.
This validation phase, however, included only those undergoing CXR and CT chest – only 2,628 of the 5,475 enrolled. The authors state “we have previously demonstrated that the clinically significant injury rate in this non-imaged group of patients approaches zero and is therefore negligible” – which certainly applies to the “major” injuries, but far less reliably to “major or minor”. However, the more important implication is for the context of use for this decision instrument. This instrument should not be applied to all trauma presentations – but, rather, to all trauma presentations for which CT chest imaging is initially judged necessary. Only then, in the subset of patients who were otherwise on-their-way to CT, would this decision instrument potentially reduce imaging. The authors do not provide its test characteristics in an all-comers population, nor provide comparative details regarding the characteristics of those imaged versus those not, so any further speculation is simply that.
As with the previously proposed NEXUS Chest, the same limitation applies – this is a one-way decision-instrument intended only to obviate CT, not inform clinicians for whom CT is needed. As such, it is subject to the cognitive biases resulting from one-way decision-instruments, paradoxically leading to increased resource utilization. It is, perhaps, the PERC rule for trauma – and do you think incorporating PERC increases, or decreases, CTPA?
“Derivation and Validation of Two Decision Instruments for Selective Chest CT in Blunt Trauma: A Multicenter Prospective Observational Study (NEXUS Chest CT)”
http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1001883