Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma
This review may be edited
Posted By: Todd Fraser
E-Mail: lil_frog@bigpond.net.au
Posted Date: 30/6/3
Title: Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma
Authors: National emergency xray utilization study group
Reference: NEJM 2000;343:94-9
Link: Click here for a direct link to the paper. A password may be required for access to fulltext.
Abstract: Background Because clinicians fear missing occult cervical-spine injuries, they obtain cervical radiographs for nearly all patients who present with blunt trauma. Previous research suggests that a set of clinical criteria (decision instrument) can identify patients who have an extremely low probability of injury and who consequently have no need for imaging studies.
Methods We conducted a prospective, observational study of such a decision instrument at 21 centers across the United States. The decision instrument required patients to meet five criteria in order to be classified as having a low probability of injury: no midline cervical tenderness, no focal neurologic deficit, normal alertness, no intoxication, and no painful, distracting injury. We examined the performance of the decision instrument in 34,069 patients who underwent radiography of the cervical spine after blunt trauma.
Results The decision instrument identified all but 8 of the 818 patients who had cervical-spine injury (sensitivity, 99.0 percent [95 percent confidence interval, 98.0 to 99.6 percent]). The negative predictive value was 99.8 percent (95 percent confidence interval, 99.6 to 100 percent), the specificity was 12.9 percent, and the positive predictive value was 2.7 percent. Only two of the patients classified as unlikely to have an injury according to the decision instrument met the preset definition of a clinically significant injury (sensitivity, 99.6 percent [95 percent confidence interval, 98.6 to 100 percent]; negative predictive value, 99.9 percent [95 percent confidence interval, 99.8 to 100 percent]; specificity, 12.9 percent; positive predictive value, 1.9 percent), and only one of these two patients received surgical treatment. According to the results of assessment with the decision instrument, radiographic imaging could have been avoided in the cases of 4309 (12.6 percent) of the 34,069 evaluated patients.
Conclusions A simple decision instrument based on clinical criteria can help physicians to identify reliably the patients who need radiography of the cervical spine after blunt trauma. Application of this instrument could reduce the use of imaging in such patients.
Are the Results Valid?
1. Was there an independent, blind comparison with a reference standard?
All patients evaluated by the tool had C-spine films. Most of those with suspcious or poorly visualised areas had CT scans. All patients were followed up and assessed clinically for evidence of a missed significant injury. All films were evaluated by a radiologist in this study.
2. Did the patient sample include an appropriate spectrum of patients to whom the diagnostic test will be applied in clinical practice?
All patients suffering "blunt trauma" and thought to be at risk of cervical spine injury were included. While no definition of this exists, the study was performed at 21 centres and is thus likely to represent clinical practice. These centres included a spectrum of trauma patient load and a variety of clinical experience.
3. Did the results of the test being evaluated influence the decision to perform the reference standard?
All patients who were included in the trial had cervical spine films performed and all had either CT or clinical follow up as the reference standard.
4. Were the methods for performing the test described in sufficient detail to permit replication?
Details for the application of the tool were not fully available. Each centre had an education package assisting practitioners to assess each of the five criteria. This information is available from the authors. The authors did make an effort to demonstrate that agreement between observers was quite high.
What are the Results?
1. Are likelihood ratios for the test results presented or data necessary for their calculation provided?
The information is available to calculate the likelihood ratios.
  • The likelihood ratio for cervical spine injury when the tool was positive was 1.14.
  • When recalculated for "significant injury" (meaning the patient was at risk if the injury was not identified), the likelihood ratio was the same.
    This indicates the tool is not good at diagnosing serious injury in patients with blunt trauma.
    However, in this study, the sensitivity was 99.0% (95%CI 98.0-99.6) for all injuries. For significant injuries this was improved to 99.6% (98.6-100%). There were only 2 false negatives from the study. The negative likelihood ratio for the tool (the odds of a negative test indicating no injury) was 0.077, indicating the usefulness of the tool as a screening test.
  • Will the Results Help Me In Caring For My Patients?
    1. Will the reproducibility of the test result and its interpretation be satisfactory in my setting?
    As the study included a vast number and variety of centres, there is no reason to suspect that it won't reflect practice in australian emergency departments.
    2. Are the results applicable to my patient?
    3. Will the results change my management?
    The study indicated that around 12% of patients previously considered for C-spine radiology could safely be treated without xrays.
    4. Will patients be better off as a result of the test?
    This may reduce the radiation exposure, financial burden, prolonged assessment time and unnecessary immobilisation associated with C-spine radiology, with little risk to patient care.

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