Accuracy of the Canadian C-spine rule and NEXUS to screen for clinically important cervical spine injury in patients following blunt trauma: a systematic review

Background:

There is uncertainty about the optimal approach to screen for clinically important cervical spine (C-spine) injury following blunt trauma. We conducted a systematic review to investigate the diagnostic accuracy of the Canadian C-spine rule and the National Emergency X-Radiography Utilization Study (NEXUS) criteria, 2 rules that are available to assist emergency physicians to assess the need for cervical spine imaging.

Methods:

We identified studies by an electronic search of CINAHL, Embase and MEDLINE. We included articles that reported on a cohort of patients who experienced blunt trauma and for whom clinically important cervical spine injury detectable by diagnostic imaging was the differential diagnosis; evaluated the diagnostic accuracy of the Canadian C-spine rule or NEXUS or both; and used an adequate reference standard. We assessed the methodologic quality using the Quality Assessment of Diagnostic Accuracy Studies criteria. We used the extracted data to calculate sensitivity, specificity, likelihood ratios and post-test probabilities.

Results:

We included 15 studies of modest methodologic quality. For the Canadian C-spine rule, sensitivity ranged from 0.90 to 1.00 and specificity ranged from 0.01 to 0.77. For NEXUS, sensitivity ranged from 0.83 to 1.00 and specificity ranged from 0.02 to 0.46. One study directly compared the accuracy of these 2 rules using the same cohort and found that the Canadian C-spine rule had better accuracy. For both rules, a negative test was more informative for reducing the probability of a clinically important cervical spine injury.

Interpretation:

Based on studies with modest methodologic quality and only one direct comparison, we found that the Canadian C-spine rule appears to have better diagnostic accuracy than the NEXUS criteria. Future studies need to follow rigorous methodologic procedures to ensure that the findings are as free of bias as possible.A clinically important cervical spine injury is defined as any fracture, dislocation or ligamentous instability detectable by diagnostic imaging and requiring surgical or specialist follow-up.^1,2 These injuries can have disastrous consequences including spinal cord injury and death if the diagnosis is delayed or missed.³ Despite the low prevalence (< 3%) of clinically important cervical spinal injury following blunt trauma (e.g., motor vehicle collision), accurate diagnosis is imperative for safe, effective management.⁴ Currently, uncertainty exists about the optimal diagnostic approach. Some guidelines^5,6 advocate using screening tools to identify patients with a higher likelihood of clinically important cervical spinal injury; these patients are then sent for imaging to establish the diagnosis. In other more conservative settings, all patients with blunt trauma are sent for imaging. The first approach, involving screening, is arguably preferable because it optimizes resources and time, while reducing unnecessary costs, radiation exposure and psychological stress for the patient.⁷ For screening to be safe and effective, the screening tools must have high sensitivity, a low negative likelihood ratio and a low rate of false positives. This assures clinicians that a clinically important cervical spine injury is unlikely and reduces the number of referrals for imaging.Clinical decision rules synthesize 3 or more findings from the patient’s history, physical examination or simple diagnostic tests to guide diagnostic and treatment decisions.^8,9 Two clinical decision rules, the Canadian C-spine rule² and the National Emergency X-Radiography Utilization Study (NEXUS; Box 1),¹⁰ are available to assess the need for imaging in patients with cervical spine injury following blunt trauma. These rules aim to reduce unnecessary imaging by reserving these investigations for patients with a higher likelihood of clinically important cervical spinal injury. Developed independently and validated using large cohorts of patients, these 2 decision rules are recommended in many international guidelines.^5,11,12 However, no consensus exists as to which rule should be endorsed.^12–14 Therefore, the purpose of our systematic review was to describe the quality of research evaluating the Canadian C-spine rule and NEXUS; describe the diagnostic accuracy of the Canadian C-spine rule and NEXUS; and compare the diagnostic accuracy of the Canadian C-spine rule to that of NEXUS.

Box 1:

National Emergency X-Radiography Utilization Study (NEXUS) low-risk criteria¹⁰

Cervical spine radiography is indicated for patients with neck trauma unless they meet ALL of the following criteria:

• No posterior midline cervical-spine tenderness
• No evidence of intoxication
• A normal level of alertness (score of 15 on the Glasgow Coma Scale)
• No focal neurologic deficit
• No painful distracting injuries