CT and NEXUS Chest CT Rules

CT has been established as the gold standard for evaluation of blunt chest trauma.¹² The NEXUS Chest CT clinical decision rules (CDRs) have been proposed to safely guide selective chest CT use in blunt trauma evaluation. A recent cost effectiveness study by the authors of the rule suggested using the rule in a hypothetical cohort of 1000 adults with blunt chest trauma in each arm suggested that the implementation of the CDR would result in 161 fewer chest CTs, at the risk of missing 0.08 clinically significant injuries. This means that 2015 more thoracic CT scans would be required to catch 1 more clinically significant injury.¹³

The rule states that if the patient has:

• a normal CXR
• no distracting injury
• no chest wall, sternum, thoracic spine or scapular tenderness

then they require no further imaging to rule out a clinically major thoracic injury. In addition, if the mechanism did not involving a rapid deceleration the patient requires no further imaging to rule out any thoracic injury.

The rule was prospectively derived then validated in eight US, urban level 1 trauma centres. They enrolled 11,477 patients 6,002 patients in the derivation phase and 5,475 patients in the validation phase.

Chest CT rule for all thoracic injuries had a sensitivity of 99.2% (95% CI 95.4%100%), a specificity of 20.8% (95% CI 19.2%22.4%), and a negative predictive value (NPV) of 99.8% (95% CI 98.9%100%) for major injury, and a sensitivity of 95.4% (95% CI 93.6%96.9%), a specificity of 25.5% (95% CI 23.5%27.5%), and a NPV of 93.9% (95% CI 91.5%95.8%) for either major or minor injury.

Chest CT for major injuries rule had a sensitivity of 99.2% (95% CI 95.4%100%), a specificity of 31.7% (95% CI 29.9%33.5%), and a NPV of 99.9% (95% CI 99.3%100%) for major injury and a sensitivity of 90.7% (95% CI 88.3%92.8%), a specificity of 37.9% (95% CI 35.8%40.1%), and a NPV of 91.8% (95% CI 89.7%93.6%) for either major or minor injury.¹⁴