PECARN Head CT Decision Rule Calculator
The PECARN decision rule helps clinicians decide whether to perform a CT scan on children with minor blunt head trauma (GCS 14–15). Select the child's age group and answer Yes/No to each clinical finding to receive a Low, Intermediate, or High risk classification.
Age group
GCS < 15 OR altered mental status (agitation, confusion, slow/inappropriate responses)
Palpable/boggy temporal or parietal scalp hematoma
Loss of consciousness ≥ 5 seconds
Any loss of consciousness < 5 seconds
Not acting normally per parent/carer
Severe mechanism of injury
Non-frontal (occipital, parietal, or temporal) scalp hematoma
Low risk — CT not routinely indicated
How does this calculator work?
PECARN stratifies children with minor blunt head trauma (GCS 14–15) by age. Under 2: GCS < 15, boggy scalp hematoma, or LOC ≥ 5 s → CT recommended; other risk factors → observe. Age 2+: GCS < 15 or basilar skull fracture signs → CT recommended; LOC, vomiting, severe headache, or severe mechanism → observe vs CT. No risk factors → CT not routinely indicated.
Formula
How this is calculated
The PECARN (Pediatric Emergency Care Applied Research Network) prediction rule was derived and validated in a prospective multicentre cohort of over 42,000 children with blunt head trauma and GCS 14–15 (Kuppermann et al., Lancet 2009). Its goal is to identify children at very low risk of clinically important traumatic brain injury (ciTBI — defined as death from TBI, neurosurgical intervention, intubation > 24 h, or hospital admission ≥ 2 nights with TBI on CT) who can safely avoid CT and its radiation exposure.
For children under 2 years, three factors immediately classify a child as High risk (CT recommended): GCS < 15 or altered mental status, a palpable or boggy temporal/parietal scalp hematoma, and loss of consciousness ≥ 5 seconds. If none are present, four Intermediate-risk factors trigger a shared decision about CT versus a period of ED observation: any LOC < 5 s, not acting normally per the parent, a severe mechanism, or a non-frontal scalp hematoma. Children with none of these factors are Low risk (< 0.02% ciTBI) and CT is not routinely indicated.
For children 2 years and older the High-risk factors are GCS < 15/altered mental status and signs of basilar skull fracture. Intermediate factors are LOC, vomiting, severe headache, and severe mechanism. The severe mechanism definition includes: motor-vehicle crash with ejection, rollover, or death of another passenger; pedestrian or cyclist without helmet struck by a motorised vehicle; fall > 0.9 m for under 2 or > 1.5 m for 2+; or head struck by a high-impact object. This tool does not substitute for individual clinical judgement, local protocols, or information not captured in the rule (e.g., coagulopathy, repeated scans, parental anxiety).
Frequently asked questions
PECARN stands for Pediatric Emergency Care Applied Research Network, a US consortium of emergency departments that conducted the multicentre study validating this head CT decision rule. The founding publication is Kuppermann N et al., Lancet 2009;374:1160–70.
Low risk means the probability of clinically important traumatic brain injury is extremely small (< 0.02%) based on the study population. CT is not routinely recommended, and close observation and parental education are the standard approach. However, the clinician retains full discretion to image if the clinical picture changes or other factors are present.
For Intermediate-risk children the PECARN rule does not mandate CT or exclude it — it identifies a group where the decision should be made jointly by the physician and family, weighing the radiation risk of CT against the small but non-negligible risk of ciTBI. Factors such as number of findings, worsening symptoms, access to follow-up, and parental preference all inform the choice.
Also known as
TG we-Calculate Editorial Team. (2026). PECARN Head CT Decision Rule Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/pecarn-calculator
TG we-Calculate Editorial Team. "PECARN Head CT Decision Rule Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/pecarn-calculator.
TG we-Calculate Editorial Team, "PECARN Head CT Decision Rule Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/pecarn-calculator
@misc{wecalculate_pecarn_calculator, title = {PECARN Head CT Decision Rule Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/pecarn-calculator}}, year = {2026}, note = {TG we-Calculate} }
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