PECARN Pediatric Head CT Calculator
This PECARN calculator applies the validated Pediatric Emergency Care Applied Research Network (PECARN) decision rule to children aged 0-17 who present within 24 hours of blunt head trauma with a GCS of 14 or 15. Select the patient age group, then answer the clinical questions to receive an immediate risk category (high, intermediate, or very low) and an evidence-based CT recommendation. The rule was derived from 42,412 children across 25 North American emergency departments and reduces unnecessary pediatric head CTs by more than 25%.
What is the PECARN rule?
The Pediatric Emergency Care Applied Research Network (PECARN) rule is a clinical decision tool for determining whether children who have sustained blunt head trauma need a CT scan of the head. It was derived from a prospective, multicenter cohort study of 42,412 children presenting to 25 North American emergency departments (Kuppermann et al., Lancet 2009). The goal was to identify which children are at very low risk of clinically important traumatic brain injury (ciTBI) and can safely avoid CT imaging, reducing unnecessary radiation exposure in a population that is particularly vulnerable to radiation-related cancer risk. The rule has two separate algorithms: one for children under 2 years and one for children aged 2 and older, reflecting the different presentations and risk factors in these groups.
How the algorithm works
PECARN divides predictors into two tiers for each age group. High-risk predictors (such as GCS of 14, altered mental status, palpable skull fracture in infants, or signs of basilar skull fracture in older children) indicate a ciTBI rate above 4%, and CT scanning is recommended. Intermediate-risk predictors (which vary by age group and include non-frontal scalp hematoma, loss of consciousness of 5 or more seconds in infants, severe mechanism of injury, not acting normally per parent, or vomiting, severe headache, and any LOC in older children) are associated with a ciTBI rate near 0.8-0.9%, and CT versus observation is left to clinical judgment. When no predictors are present in either tier, the ciTBI risk is below 0.02%, and CT is not recommended. CT instead delivers roughly 2-4 mSv of radiation, equivalent to 8-12 months of natural background exposure, with an estimated lifetime excess cancer risk of about 1 in 10,000 for a child.
What counts as a clinically important TBI (ciTBI)?
The PECARN study defined ciTBI as any of the following: death from TBI, neurosurgical intervention (including craniotomy, intracranial pressure monitoring, or elevation of a depressed skull fracture), intubation for more than 24 hours for TBI management, or hospital admission of 2 or more nights for TBI. This definition was chosen to focus the rule on outcomes that actually matter clinically, rather than incidental findings on CT that do not change management.
Who this tool applies to - and who it does not
PECARN applies to children presenting within 24 hours of blunt head trauma with a GCS of 14 or 15. It does not apply to children with a GCS of 13 or lower (who require CT regardless), penetrating trauma, known VP shunts or brain tumors, bleeding disorders or anticoagulation use, or trivially minor mechanisms in completely asymptomatic children. Infants younger than 3 months may need lower thresholds for CT even in low-risk categories, and any concern for non-accidental injury (NAI) or child abuse is an independent indication for CT regardless of PECARN score. The 4-6 hour observation period is measured from the time of injury, not from arrival in the emergency department.
Intermediate-risk: CT or observation?
The intermediate-risk group is where clinical judgment is most important. Factors that may favor CT over observation include: very young age, physician concern, caregiver preference or inability to reliably observe the child at home, multiple intermediate-risk factors, isolated mechanism without other reassuring features, worsening symptoms during the initial assessment period, or practical barriers to returning quickly if the child deteriorates. Factors that may favor observation include: a single intermediate predictor, mild LOC, a reassuring exam, a cooperative and reliable caregiver, and easy access to medical care. Either approach is consistent with the PECARN evidence base when intermediate-risk factors are the only findings.
PECARN risk categories and ciTBI rates
| Age group | Risk category | ciTBI rate | CT recommendation |
|---|---|---|---|
| <2 years | High risk (>=1 high-risk factor) | 4.4% | CT recommended |
| <2 years | Intermediate risk (>=1 intermediate, no high) | 0.9% | CT or 4-6 hr observation |
| <2 years | Very low risk (no factors) | <0.02% | CT not recommended |
| >=2 years | High risk (>=1 high-risk factor) | 4.3% | CT recommended |
| >=2 years | Intermediate risk (>=1 intermediate, no high) | 0.8% | CT or 4-6 hr observation |
| >=2 years | Very low risk (no factors) | <0.02% | CT not recommended |
From Kuppermann et al., Lancet 2009 (n=42,412). ciTBI = clinically important traumatic brain injury (death from TBI, neurosurgical intervention, intubation >24 hours, or hospital admission >=2 nights).
Frequently asked questions
What does PECARN stand for?
PECARN stands for Pediatric Emergency Care Applied Research Network, a consortium of pediatric emergency medicine research centers across North America. The PECARN head CT rule was published in The Lancet in 2009 by Kuppermann and colleagues, based on a prospective study of over 42,000 children with head trauma.
Can I use PECARN for adults?
No. PECARN is validated only for pediatric patients under 18 years of age. Adult head injury decision rules such as the Canadian CT Head Rule or the New Orleans Criteria should be used for adults. The biology of head trauma and the specific risk factors differ substantially between children and adults.
What is the difference between the under-2 and over-2 algorithms?
Both algorithms share the GCS-14 or altered mental status criterion as a high-risk factor. The under-2 algorithm uses palpable skull fracture as the second high-risk predictor and non-frontal scalp hematoma, LOC of 5 seconds or more, severe mechanism (fall over 0.9 m), and not acting normally per parent as intermediate predictors. The over-2 algorithm uses signs of basilar skull fracture as the second high-risk predictor and vomiting, any LOC, severe mechanism (fall over 1.5 m), and severe headache as intermediate predictors.
What should happen during the 4-6 hour observation period?
During the observation period, the clinical team monitors for deteriorating GCS, persistent or increasing vomiting (particularly three or more episodes), a worsening headache, new neurological signs (weakness, ataxia, visual changes), or behavioral change noted by the caregiver. Any deterioration during observation is an indication to proceed with CT. The observation window is measured from the time of injury, not from arrival at the department.
Does a very low PECARN risk mean the child is definitely fine?
No clinical rule is perfect. A PECARN very low risk classification means the probability of a ciTBI is less than 0.02% based on the derivation cohort, but it does not guarantee absence of injury. All families should receive written head injury advice and clear return precautions: return immediately if the child develops worsening headache, repeated vomiting, unusual sleepiness or difficulty waking, seizure, weakness, or behavioral change.
Why does PECARN use different fall heights for the two age groups?
The cut-offs reflect the level of energy transfer likely to cause significant injury at different developmental stages. For infants under 2, a fall from more than 0.9 m (about 3 feet, roughly the height of a standard table) is considered severe because even lower-energy impacts can cause significant injury in very young children. For older children, the threshold is 1.5 m (about 5 feet), as older children have more protective mechanisms and proportionally different skull anatomy.
Does this calculator replace clinical assessment?
No. PECARN is a decision support tool, not a substitute for full clinical assessment. Important factors not captured in the rule - such as physician gestalt, specific injury characteristics, socioeconomic context, caregiver reliability, and access to follow-up - should all inform the final decision. The intermediate-risk group in particular requires individualized judgment. This calculator provides guidance only; always apply institutional protocols and senior clinical oversight.