This is the first in a blog series that will explore landmark articles in Emergency Medicine.
- Patients meeting the following five simple clinical criteria are safe to clear without cervical spine imaging following blunt trauma:
- No focal neurologic deficit
- Normal alertness
- No intoxication
- No midline posterior bony cervical spine tenderness, and
- No painful distracting injury
- The sensitivity and specificity of the NEXUS criteria for detecting low probability injury and avoiding unnecessary imaging was 99 and 12.9 percent respectively, with a negative predictive value of 99.8 percent for the detection of clinically significant injuries.
Level of evidence: 1 (Prospective cohort trial)
Based on the ACEP grading scheme for diagnostic questions the NEXUS trial receives a class of evidence rating of 1.
Blunt trauma is a frequent cause of emergency department visits. However, the overall prevalence of cervical spine injury is generally only between 2-4% (2.4% in the NEXUS cohort). The goal of the NEXUS group was to create a simple clinical tool with which to risk stratify patients following blunt trauma, thereby reducing unnecessary cervical spine imaging and subsequently improving patient care through cost-reduction and a decrement in the downstream oncogenic risk secondary to radiation exposure. The group enrolled all patients presenting to emergency departments with blunt trauma who were having cervical spine imaging. A NEXUS voucher system was used to prompt the medical team to apply a 5-point decision instrument based in clinical criteria to each patient prior to obtaining imaging. These criteria included determining the presence or absence of a focal neurologic deficit, intoxication, normal mental status, midline posterior cervical spinal tenderness and distracting injury. Of the 34,069 patients who underwent cervical spinal imaging, only 818 had significant cervical spinal injury. 810 of them were correctly identified by the NEXUS criteria as high-risk, while all others were correctly identified as low-risk patients not requiring spinal radiography. This resulted in a sensitivity of 99% and a specificity of 12.9% for the detection of low probability injury, with a negative predictive value of 99.8% and positive predictive value of 2.7%. The study was limited in its observational nature, which may have failed to capture patients with cervical injury who did not undergo spinal imaging, but may have met the decision-instrument criteria for imaging. Given the publication date it also failed to differentiate between the ability of CT versus plain film radiography in the detection of significant or operative injuries. A more recent study evaluated the NEXUS criteria in light of the significant improvement in cervical spine evaluation offered by CT imaging, calling into question the validity of the NEXUS conclusions. In this dissenting study, 2606 patients were evaluated at a level I trauma center with a notably higher prevalence of cervical spinal injury (6% versus 2.4%), finding that the NEXUS criteria had a significantly poorer sensitivity and negative predictive value of 59.4% and 97.5%, respectively when using CT imaging as the gold standard. However, the current Eastern Association for the Surgery of Trauma guidelines continue to support the use of NEXUS criteria for clinical clearance, but caution that further research may find that CT imaging reveals clinically significant injuries not detected with NEXUS criteria alone.
The NEXUS criteria was prospectively applied to 34,069 patients as part of a large multicenter prospective trial including all patients with blunt trauma presenting to a variety of different emergency departments including community, public, private, and tertiary teaching hospitals across all levels of trauma categorization. Of those enrolled, 818 demonstrated radiographic evidence of cervical spine injury. This demonstrated an overall sensitivity of 99% (95% CI: 98-99.6) and a negative predictive value of 99.8% (95% CI: 99.6-100). A total of 8 patients out of 818 with significant cervical spine injury were incorrectly identified as low-risk by the NEXUS criteria, one of which was likely not clinically relevant and subacute in nature. When considering patients with clinically significant injuries the respective sensitivity and negative predictive value increased to 99.6 and 99.9% respectively. In this dataset 12.6% or 4,309 patients could have been spared imaging. Prior to this prospective trial in the New England Journal of Medicine, a comprehensive methodological study was completed and . The only individuals excluded were those who did not undergo imaging of the cervical spine. A key question of the methodological study was to calculate an appropriate sample size to ensure that a high sensitivity and negative predicative value could be achieved. An ongoing controversy that continues to surround the NEXUS trial is that some of the five criteria for low probability injury were somewhat vague in their wording. During the training sessions for the prospective arm, however, possible interpretations were reviewed particularly with regards to the concept of a “distracting injury,” and this information was available to the clinicians using the NEXUS computer. The interobserver reliability of the criteria used in the final decision-instrument was also noted to be excellent (k = 0.73). Notably only 2.5% of study participants were less than 8 years old so the recommendations regarding use in pediatrics remains disputed.
See Figure “Instructions to Participating Physicians,” in the methodology study from Annals of Emergency Medicine. Who knew that an “inability to remember 3 objects at 5 minutes,” was a criterion for altered neurologic function in the NEXUS retrospective review? Also included in this figure is the more controversial description of a distracting injury.
Look out for ongoing discussion of the most recent cervical spine article published in February 2015 in the Journal of Trauma by Mayur and his colleagues for using CT to clear the cervical spine of obtunded patients following blunt trauma.
Stay tuned for more to come for Ian Stiell and co. before we tune back in to our curriculum.
The Canadian C-Spine Rule for Radiography in Alert and Stable Trauma Patients.
The Canadian CT Head Rule for patients with minor head injury.
J.Hoffman, W. Mower, A. Wolfson, et al. “Validity of a Set of Clinical Criteria to Rule Out Injury to the Cervical Spine in Patients With Blunt Trauma.” NEJM, July 2000; 343(20):94-99
J.Hoffman, A. Wolfson, K. Todd, et al. “Selective Cervical Spine Radiography in Blunt Trauma: Methodology of the National Emergency X-Radiography Utilization Study (NEXUS).” Annals of Emergency Medicine, Oct 1998; 32(4): 461-9
Duane, J. Mayglothling, S. Wilson, et al. “National Emergency X-Radiography Utilization Study Criteria is Inadequate to Rule Out Fracture After Significant Blunt Trauma Compared with Computed Tomography.” Journal of Trauma, April 2011; 70(4): 829-31
Patel, MB. Humble, SS. Cullinane, DC. et al. “Cervical Spine Collar Clearance in the Obtunded Blunt Trauma Patient: A Systematic Review and Practice Management Guideline from the Eastern Association for the Surgery of Trauma.” Journal of Acute Care Surgery. February 2015; 78(2): 430-41
Anatoly Kazakin, MD