The LIMIT clinical decision instrument reduces neuroimaging compared to unstructured clinician judgement in recurrent seizures

Abstract

Introduction: Given the many causes of seizures, emergency physicians often utilize brain computed tomography (CT) to evaluate for intracranial pathology. Previously, we have validated the LIMIT (Let's Image Malignancy, Intracranial Hemorrhage, and Trauma) clinical decision instrument (CDI) study to determine which patients with recurrent seizures require emergent neuroimaging. The LIMIT CDI had a negative predictive value (NPV) of 99.9%. Here, we seek to compare the LIMIT CDI to unstructured physician judgement.

Methods: This was an observational study of patients who presented with a complaint of seizure. A research assistant reviewed the electronic medical record (EMR) for each patient and applied the LIMIT CDI. Brain CT was used as a proxy for physician judgement. If no brain CT was ordered and the patient was discharged from the emergency department (ED), the EMR was searched to determine whether patient had any medical visits within one year of the index visit. If the patient had no new neurological findings on follow up or abnormalities on follow up neuroimaging, this was considered a patient who did not require a brain CT in the ED. Patients who did not have a CT on their ED visit and had no follow up visits were excluded.

Results: 1739 patients were screened and 1108 patients were in the final analysis. 24 patients who did not have a brain CT and no follow up visits were excluded. 10 patients (0.9%) had positive CTs. 9/10 of the patients were identified by the CDI resulting in a sensitivity of 90%, specificity of 81.1% and a negative predictive value (NPV) of 99.9%, and a negative likelihood ratio (LR) of 0.12. Clinician judgement identified all 10 patients with a positive brain CT for a sensitivity of 100%, specificity of 67.8%, and a NPV and negative LR of 100% and 0, respectively. Using unstructured clinical judgement, EPs ordered 364 brain CTs while only 217 brain CTs would have been ordered using the CDI, a reduction of 13.3%.

Discussion: When compared to unstructured physician judgement, the LIMIT CDI would have reduced brain CT usage by more than 13%. Although the LIMIT CDI needs to be validated in a larger set of patients, it performed better than unstructured physician judgement for evaluating need for emergent neuroimaging after recurrent seizures.

Keywords: Clinical decision instruments; Computed tomography; Neuroimaging; Seizure.