The simple CHIP prediction rule uses 10 major and 8 minor risk factors to decide whether head CT is indicated after minor head injury. In the original publication, a CT scan is recommended if at least 1 major or at least 2 minor criteria are present in a patient within the derivation population.

This implementation assigns 2 points to each major criterion and 1 point to each minor criterion. The total CHIP score is the sum of all selected criteria. A total score ≥2 is mathematically equivalent to the published rule of "at least 1 major or at least 2 minor" and is treated as "CT indicated".

Category	Risk factor	Definition in CHIP simple rule	Points in this calculator
Major	Pedestrian or cyclist versus vehicle	Blunt trauma as a pedestrian or cyclist struck by a motor vehicle	2
Major	Ejected from vehicle	Ejection from a motor vehicle during the incident	2
Major	Vomiting	Any episode of vomiting after the traumatic event	2
Major	Post-traumatic amnesia ≥4 hours	Patient cannot recall events for ≥4 hours after trauma	2
Major	Clinical signs of skull fracture	Injury suggesting skull fracture (e.g. palpable discontinuity, CSF leak, raccoon eyes, bleeding from ear)	2
Major	GCS score <15 at presentation	Initial GCS 13 or 14 in the ED	2
Major	GCS deterioration ≥2 points	Drop of ≥2 GCS points 1 hour after presentation	2
Major	Use of anticoagulant therapy	Current systemic anticoagulant treatment	2
Major	Post-traumatic seizure	Witnessed or suspected seizure after injury	2
Major	Age ≥60 years	Age 60 years or older	2
Minor	Fall from any elevation	Any fall mechanism	1
Minor	Persistent anterograde amnesia	Short-term memory deficit persisting after initial assessment	1
Minor	Post-traumatic amnesia 2 to <4 hours	Post-traumatic amnesia duration between 2 and less than 4 hours	1
Minor	Contusion of the skull	Skull contusion without signs of fracture	1
Minor	Neurologic deficit	Any focal deficit on routine neurological examination	1
Minor	Loss of consciousness	Any witnessed or reported loss of consciousness	1
Minor	GCS deterioration of 1 point	Drop of 1 GCS point 1 hour after presentation	1
Minor	Age 40–60 years	Age between 40 and 60 years (inclusive)	1

Interpretation: CHIP score 0–1 = low risk (CT often not required if no other red flags). CHIP score ≥2 = not low risk (CT usually indicated).

CHIP (CT in Head Injury Patients) Prediction Rule