Background: The National Emergency X-Radiography Utilization Study (NEXUS) recently validated the ability of a decision instrument to define a population with an extremely low risk of cervical spine injury (CSI) after blunt trauma. It is unclear whether each of the 5 individual criteria is necessary for the decision instrument to maintain its high sensitivity.
Methods: NEXUS was a prospective observational study at 21 emergency departments, which enrolled all patients with blunt trauma for whom cervical spine radiographs were ordered. In this substudy, we examined the NEXUS database to determine the contribution of each of the 5 individual low-risk clinical criteria to the overall sensitivity of the decision instrument.
Results: All but 8 of 818 patients with CSI, and all but 2 of 578 patients with significant CSI, were identified by using the decision instrument. A substantial number of patients with CSI (236/818 [29%]) and patients with significant CSI (175/578 [30%]) met only 1 of the 5 non--low-risk criteria, and each of the 5 criteria was the only indicator of non--low-risk status in at least 8 patients with CSI and at least 5 patients with significant CSI.
Conclusion: Because each of the 5 low-risk criteria was the only marker of non--low-risk status in at least a few patients with significant CSI, modification of the overall NEXUS decision instrument by eliminating any one of the criteria would markedly reduce sensitivity and make the instrument unacceptable for clinical use.