Background: Computed tomography (CT) can provide critical information for diagnosis and is a prevalent and easy-to-use imaging test, but overtesting becomes a big problem. The previous report showed 30-40% of abdominal CT scans were medically unnecessary. Therefore, head CT is a research topic in overtesting, and clinical predictive scores have been developed to avoid overtesting of head CT. Canadian CT Head Rule (CCHR) is a clinical predictive score for mild head trauma. It is a score for detecting patients who require neurosurgical intervention, but does not require neurosurgical intervention and does not require CT imaging. It is also useful for detecting over-diagnosis with a score that is also useful for detecting. However, 70% of head trauma patients have not been tested for CCHR, and it is known that CCHR is problematic in clinical practice. Japan has the most significant number of CTs per population in the world. There are no studies that have searched for the proportion of head CT performed properly using clinical prediction scores.

Methods: Our research proposal is to investigate how frequently is head CT scan ordered inappropriately for patients with a head injury in a Japanese hospital. All head CT orders for patients with a head injury in ED in Urasoe General Hospital from April 2019 to May 2019 were included. Exclusion criteria were patients who did not provide consent to participate in the study and on baseline anticoagulation/antiplatelet drugs.The primary outcome was the number of head CT ordered inappropriately among patients who were considered at low risk by standard rules. The secondary outcome was the CT scans rate for other body sites and physicians rate who ordered head CT scans (PGY 1, 2, or other).

Results: The median age was 41. The rate of CT scans for other sites was 22%. Overtesting rates of head CT with minor head injury were 86.7%(95%CI 0.7345-0.9412). Inappropriate CT scans rate in all head CT scans was 45.9%. Of the inappropriate CT scans, 48% were ordered by PGY1.

Conclusions: We show there is a high proportion of overtesting in CT scan use for patients with a minor head injury. Educational efforts for junior residents are needed to improve the value of care in the ER. Additional research is needed because there may be many potentially inappropriate tests.