External Validation of a Tool to Identify Low-Risk Patients With Isolated Subdural Hematoma and Preserved Consciousness

Study objective: The SafeSDH Tool was derived to identify patients with isolated (no other type of intracranial hemorrhage) subdural hematoma who are at very low risk of neurologic deterioration, neurosurgical intervention, or death. Patients are low risk by the tool if they have none of the following: use of anticoagulant or nonaspirin antiplatelet agent, Glasgow Coma Score (GCS) <14, more than 1 discrete hematoma, hematoma thickness >5 mm, or midline shift. We attempted to externally validate the SafeSDH Tool. Methods: We performed a retrospective chart review of patients aged ≥16 with a GCS ≥13 and isolated subdural hematoma who presented to 1 of 6 academic and community hospitals from 2005 to 2018. The primary outcome, a composite of neurologic deterioration (seizure, altered mental status, or symptoms requiring repeat imaging), neurosurgical intervention, discharge on hospice, and death, was abstracted from discharge summaries. Hematoma thickness, number of hematomas, and midline shift were abstracted from head imaging reports. Anticoagulant use, antiplatelet use, and GCS were gathered from the admission record. Results: The validation data set included 753 patients with isolated subdural hematoma. Mortality during the index admission was 2.1%; 26% of patients underwent neurosurgical intervention. For the composite outcome, sensitivity was 99% (95% confidence interval [CI] 97 to 100), and specificity was 31% (95% CI 27 to 35). The tool identified 162 (21.5%) patients as low risk. Negative likelihood ratio was 0.03 (95% CI 0.01 to 0.11). Conclusion: The SafeSDH Tool identified patients with isolated subdural hematoma who are at low risk for poor outcomes with high sensitivity. With prospective validation, these low-risk patients could be safe for management in less intensive settings.