Pecarn Calculator - Pediatric Head CT Decision Rule

A pecarn calculator applies the Pediatric Emergency Care Applied Research Network clinical decision rule to children with minor blunt head trauma and returns a ciTBI risk band with a recommended next step. The rule was derived on 42,412 children across 25 PECARN emergency departments and is one of the most widely used pediatric head injury screening tools in modern emergency medicine.

• • Pre-CT discussion in the emergency department: review the PECARN predictors at triage so the conversation with the family starts from a structured risk band.
• • Urgent care or pediatric office triage: use the rule to decide whether to observe in clinic, transfer to a pediatric ED, or arrange imaging for a child with a minor head injury.
• • Parental shared decision making: share the same risk band and ciTBI percentage with the family so the imaging choice is grounded in a number the family can read.

PECARN is intended for children with GCS 14 to 15 after a blunt head injury, no trivial mechanism, and no known brain tumor, ventricular shunt, or bleeding disorder. Outside that scope the rule is not validated.

The same pediatric ED visit often pairs a head injury review with a vital sign check, and the Pediatric Blood Pressure Calculator applies age-aware systolic and diastolic cut-offs to a triage measurement that sits in the same chart as the PECARN band.

The pecarn calculator first picks the correct age arm from the patient age, then asks about the published predictors in that arm. The answer is mapped to one of three risk bands with a published ciTBI rate and a recommended next step.

• ageGroup: lt2 (<2 years) or ge2 (>=2 years). The 2009 study used these two arms.
• alteredMentalStatus: GCS <=14, agitation, somnolence, slow response, or repetitive questions. High risk in both arms.
• basilarSkullFractureSigns: Hemotympanum, raccoon eyes, CSF otorrhea or rhinorrhea, or Battle sign. High risk in both arms.
• lossOfConsciousness: LOC >=5 seconds in the <2 years arm, or any LOC in the >=2 years arm.
• vomiting: Any vomiting after the head injury. Intermediate risk in both arms.
• severeMechanism: Motor vehicle crash with ejection, pedestrian struck, fall above the age-specific height, or high-impact object. Intermediate risk in both arms.
• severeHeadache: Severe headache reported by the patient. Used only in the >=2 years arm.
• actingAbnormal: Parent report of lethargy, not eating, not playing, or not acting like themselves. Used only in the <2 years arm.

The two high-risk predictors are altered mental status and basilar skull fracture signs. The <2 years arm reported 0.02 percent, 0.9 percent, and 4.4 percent in the very low, intermediate, and high risk groups. The >=2 years arm reported 0.05 percent, 0.9 percent, and 4.3 percent in the same three groups.

According to Kuppermann N et al., Lancet 2009, the PECARN rule stratifies 42,412 children into very low risk, intermediate risk, and high risk groups for clinically important traumatic brain injury using two age-specific prediction rules.

The mental status component of the rule mirrors the activity and grimace items used in newborn assessment, so the Apgar Score Calculator is a natural earlier-life companion that uses the same quick bedside scoring approach.

Four concepts drive the result. Naming them keeps the calculator from being read as a stand-alone CT trigger.

A 6-year-old with one vomit and a severe mechanism but no AMS and no basilar skull fracture signs sits in the intermediate risk band.

The age arm choice and the age-specific fall height threshold both depend on the child's growth chart, and the BMI Percentile Child Calculator returns the same age-and-sex percentile number used in pediatric documentation.

The form works from a small set of yes-or-no predictors. Each input should be set from a recent exam, history, or mechanism statement.

1. 1 Pick the age arm: set the patient age group to less than 2 years for infants and toddlers, and 2 years or older for children aged 2 through 17.
2. 2 Mark the two high-risk predictors: set altered mental status only if the GCS is 14 or lower, or the child is agitated, somnolent, or slow to respond. Set basilar skull fracture signs only if hemotympanum, raccoon eyes, CSF leak, or Battle sign.
3. 3 Mark the intermediate-risk predictors: set LOC using the 5-second cut-off in the infant arm and any LOC in the child arm. Set vomiting, severe mechanism, severe headache (child arm), and acting abnormal per parent (infant arm).
4. 4 Read the band and the next step: the result panel shows the PECARN risk band, the ciTBI percentage, the age arm, the count of positive predictors, and a note that maps the band to CT, observation, or no CT.
5. 5 Share the band with the family: write the band, the ciTBI percentage, and the date and time on the visit note so the next clinician and the family can compare it with their own findings.

A reader who arrives with an 18-month-old who fell from a couch, has no LOC, no vomiting, and is acting normally sets age group to <2 years, leaves all six predictors at 0, and reads a very low risk band with a 0.02 percent ciTBI rate. The recommended next step is to provide head injury care instructions and observe at home.

When a child with a minor head injury also needs an outpatient prescription for an unrelated infection, the Amoxicillin Pediatric Dosage Calculator turns the same weight and age into a single mg per kg dose that can be written on the same visit note.

Using a pecarn calculator offers several practical advantages over free-text description alone.

• • Validated pediatric rule: the rule was derived on 42,412 children in the 2009 PECARN study and is one of the most validated pediatric head injury decision rules in modern emergency medicine.
• • Age-aware predictor set: the form switches between the <2 years and the >=2 years arms, so severe headache and acting abnormal per parent only appear when clinically useful.
• • Three-band output with a clear next step: the band is paired with a published ciTBI rate and a recommended next step, so the same number drives documentation, communication, and disposition.
• • Shared care-team language: triage, primary care, urgent care, emergency medicine, and pediatric neurosurgery can all read the same band, which keeps the discussion focused on the rule and the next test.

Preterm infants and toddlers in the <2 years arm often need corrected-age documentation, and the Adjusted Age Calculator returns the adjusted age in months and years that travels with the PECARN band.

The output depends on the predictors entered and on the patient. Small changes can move the result between bands.

• • PECARN is a screening tool, not a stand-alone CT trigger. The imaging choice still depends on the clinical exam, the family's preferences, and the local imaging resources.
• • The rule was derived in 25 PECARN emergency departments in the United States and Canada, so local CT availability and follow-up access can change the next step.

According to NICE NG232 Head Injury Guideline, PECARN is one of the validated pediatric clinical decision rules used together with clinical judgment, observation, and shared decision making rather than as a stand-alone CT trigger.

According to American Academy of Pediatrics / CDC Pediatric mTBI Guideline, PECARN predictors and age-specific severe mechanism thresholds should be paired with clinical observation and shared decision making before ordering a CT head.

Older children who need a second age-aware rule-out tool before imaging is ordered can use the Age-Adjusted D-Dimer Calculator, which applies a similar age-aware threshold to a different clinical question.