Best Evidence Topics

Decision rule

Marion Smits
Predicting Intracranial Traumatic Findings on Computed Tomography in Patients with Minor Head Injury
Annals of Internal Medicine
2007;397-405
  • Submitted by:Timothy VanderKooy - Medical Student
  • Institution:Wayne State University School of Medicine
  • Date submitted:3rd October 2009
Before CA, i rated this paper: 5/10
1 Objectives and hypotheses
1.1 Are the objectives of the study clearly stated?
  Yes, The objective was to develop a prediction rule for the use of CT in patients with minor head injury.
2 Design
2.1 Is the study design suitable for the objectives?
  Yes, the study examined a large number of patients presenting to the hospital after mild head trauma and reviewed the history of each accident in an attempt to develop a decision rule reguarding when to obtain a head CT.
2.2 Who / what was studied?
  3181 patients were studied who presented to 1 of 4 Dutch hospitals with mild head trauma and the following inclusion criteria: presentation within 24 hours, age of atleast 16 years, and GCS of 13 or 14, or GCS of 15 with one of the following risk factors- loss of consciousness, short-term memory deficit, amnesia, posttraumatic seizure, vomiting, severe headache, intoxication with alcohol or drugs, use of anticoagulants, external head injury, or neurologic deficit.
2.3 Was this the right sample to answer the objectives?
  Yes, although the study neglected to obtain CT information on patients who presented with a GCS of 15 and didn't have any identifiable risk factors for intracranial pathology.
2.4 Is the study large enough to achieve its objectives? Have sample size estimates been performed?
  Yes, the study included enough patients to obtain at least ten patients with positive CT findings for each of the 25 variables they were measuring. This required 3125 patients given an 8 percent incidence of traumatic findings on head CT
2.5 Were all subjects accounted for?
  No, of their initial study 71 patients were excluded because of improper workup or history taking. Also only 62 percent of the patients included had a complete history reporting results for each of the 25 risk factors measured in the study.
2.6 Were all potential predictors included during derivation?
  No, however, it would be impossible to consider every possible predictor reguarding intracranial damage after head injury.
2.7 Were all appropriate outcomes considered?
  Yes, they considered whether if was intracranial pathology on CT scan and also whether or not there was need for neurosurgical intravention.
2.8 Has ethical approval been obtained if appropriate?
  Ethical approval was not required as every patient enrolled in the study would have recieved the same workup either way.
2.9 Has the decision rule been validated?
  Yes, through internal validation.
2.10 Are the derivation and validation data set independent?
  No.
3 Measurement and observation
3.1 Is it clear what was measured, how it was measured and what the outcomes were?
  Yes, patients were being measured for the presence or absence of intracranial CT findings and neurosurgical intervention in association with 25 seperate risk factors for worsened prognosis after head trauma.
3.2 Are the measurements valid?
  Yes, they appear to be valid.
3.3 Are the measurements reliable?
  Yes, examinations were performed by a neurologist and head CTs were read by a neuroradiologist or trauma radiologist.
3.4 Are the measurements reproducible?
  Yes, this study can be duplicated by any facility with a neurologist and a neuroradiologist.
4 Presentation of results
4.1 Are the basic data adequately described?
  Yes, the data is well presented in tables indicating the predictive values of each of a variety of risk factors for intracranial pathology as well as the sensitivity and specificity of the decision rule in regards to the use of head CT.
4.2 Are the results presented clearly, objectively and in sufficient detail to enable readers to make their own judgement?
  Yes, the complete data presented in the appendices allow the reader to verify the authors conclusions.
4.3 Are the results internally consistent, i.e. do the numbers add up properly?
  Yes
5 Analysis
5.1 Are the data suitable for analysis?
  Yes, although it is concerning that 38 percent of the study patients had complete histories for every risk factor being investigated.
5.2 Are the methods appropriate to the data?
  Yes
5.3 Are any statistics correctly performed and interpreted?
  Yes, the nominal variables were measured using chi-square analysis, the ordinal variables were measured with the Mann-Whitney U test, and the continuous variables were measured using the unpaired 2-tailed t-test.
6 Discussion
6.1 Are the results discussed in relation to existing knowledge on the subject and study objectives?
  Yes, the decision rule created with this study was compared to the New Orleans Criteria for Head CT and the Canadian CT Head Rule.
6.2 Is the discussion biased?
  Yes, the authors propose the superiority of thier decision rule to previously published head CT criteria.
7 Interpretation
7.1 Are the authors' conclusions justified by the data?
  Yes, this rule is 100 percent sensitive in ruling out intracranial pathology requiring neurosurgical intervention and should be a safe method for reducing the number of CT scans required for mild head trauma.
7.2 What level of evidence has this paper presented? (using CEBM levels)
  IIB as this is a clinical decision rule validated with split sample analysis
7.3 Does this paper help me answer my problem?
  Yes, this is a safe rule for determining the need for head CT in patients fitting the groups sample. However, it does not address CT indications for patients with a GCS of 15 not meeting one of the before mentioned criteria.
After CA, i rated this paper: 5/10
8 Implementation
8.1 Can this decision rule be implemented in practice?
  Yes, this rule is 100 percent sensitive in ruling out intracranial pathology requiring neurosurgical intervention and should be a safe method for reducing the number of CT scans required for mild head trauma.
8.2 What aids to implementation exist?
  This is an simple rule to follow, and the authors have a website available to help calculate a score for the risk of intracranial pathology in patients.
8.3 What barriers to implementation exist?
  Due to the concerns about liability and differences in clinical judgement, I do not believe many physicians would be willing to use this rule routinely in patients with head trauma.