Kerstin de Wit: Derivation of a clinical decision rule for emergency department head CT scanning in seniors who have fallen.

Background and Importance: There is a major evidence gap in the study of brain injury diagnosis among seniors. Over 80% of traumatic intracranial bleeding in older adults is cause by a fall on level ground. Fall-associated head injuries are rising, as is the mortality from this condition. Diagnostic tools for risk stratification of these patients are lacking in the emergency setting.

The incidence of intracranial bleeding in elderly emergency department patients who have fallen is 5%. Currently, up to 75% of these patients receive a head CT scan which can prolong the emergency department stay. Only one in 15-25 head CT scans are positive for intracranial bleeding. One in 100 patients who do not receive a head CT are subsequently found to have an intracranial bleed.

Goal: Our study aim is to derive a clinical decision rule which will identify older adults who present to the emergency department after a fall who have no risk of intracranial bleeding and do not require a head CT scan. This will be a highly sensitive rule which will also reduce the overall number of head CT scans.

Methods: The study will enroll 4000 patients >65 years of age who attend the emergency departments of 7 Canadian hospitals after a fall. Inclusion criteria are having had a fall on level ground, out of bed, off a chair or down one step within the previous 48 hours. The treating emergency physician will complete a study assessment form to document the presence or absence of potential predictors of intracranial bleeding. Patients undergo a standardized assessment and head CT according to study protocol. Each patient is followed up for six weeks.

The primary outcome is intracranial bleeding regardless of size and location, determined by adjudication by the study neurologist and neurosurgeon, blinded to clinical information. The secondary outcomes are length of stay in the emergency department, admission/outpatient clinic/family physician follow up for intracranial bleeding and in-hospital mortality.

Predictor variables found to be both reliable (kappa>0.6) and strongly associated with the primary outcome on univariate analysis (P<0.05) will be combined using multivariate analysis. The final derived rule will only be acceptable if there is a sensitivity ≥ 99%, adequate specificity to reduce head CT scanning to <40% of all patients and fewer than seven component variables.

Expertise: This is a Canada-wide collaboration between emergency, geriatrics, neurology, neurosurgery and thrombosis medicine. Our study team includes world leading research experts in emergency medicine clinical decision rules, emergency diagnostic studies and falls in the elderly. The study has data management and statistical support through McMaster University.

Expected Outcomes: This is the derivation phase of our program. We expect to find 160 episodes of intracranial bleeding within our cohort of 4000 patients. We will develop a simple, reliable clinical decision rule which will identify a minority of patients who require a head CT scan in the emergency department. The rule will allow for more rapid processing of the majority of patients do not require a head CT. The future validation phase of our program will confirm these findings.

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