Pecarn Head Ct Calculator
Determine if a child with minor head trauma needs a CT scan using PECARN decision rules. Enter values for instant results with step-by-step formulas.
Formula
PECARN Risk = High / Intermediate / Very Low based on age-specific clinical predictors
For children < 2 years: High-risk predictors are GCS < 15, altered mental status, and palpable skull fracture. Intermediate predictors are occipital/parietal/temporal scalp hematoma, LOC >= 5 seconds, severe mechanism, and not acting normally. For children >= 2 years: High-risk predictors are GCS < 15, altered mental status, and basilar skull fracture signs. Intermediate predictors are vomiting, LOC, severe headache, and severe mechanism.
Worked Examples
Example 1: Infant Fall from Changing Table
Problem: An 8-month-old fell from a changing table (approximately 3.5 feet). The child cried immediately, has a large occipital scalp hematoma, GCS is 15, no altered mental status, no palpable skull fracture, and the parent says the child seems slightly fussier than normal.
Solution: PECARN Algorithm (< 2 years):\nGCS < 15: No\nAltered Mental Status: No\nPalpable Skull Fracture: No\n=> Not High Risk\n\nIntermediate Predictors:\nOccipital Scalp Hematoma: YES\nLOC: No\nSevere Mechanism: YES (fall > 3 feet for < 2 yr)\nActing Normally: Questionable (fussier)\n=> Intermediate Risk (ciTBI risk ~0.9%)
Result: INTERMEDIATE RISK | ciTBI ~0.9% | Observation 4-6 hours vs CT (shared decision-making)
Example 2: School-Age Child with No Risk Factors
Problem: A 7-year-old tripped and hit their forehead on the ground at school. No loss of consciousness. GCS 15. No vomiting, no headache, acting normally. Ground-level fall.
Solution: PECARN Algorithm (>= 2 years):\nGCS < 15: No\nAltered Mental Status: No\nBasilar Skull Fracture Signs: No\n=> Not High Risk\n\nIntermediate Predictors:\nVomiting: No\nLOC: No\nSevere Headache: No\nSevere Mechanism: No (ground-level fall)\n=> Very Low Risk (ciTBI risk <0.05%)
Result: VERY LOW RISK | ciTBI <0.05% | CT NOT recommended | Discharge with return precautions
Frequently Asked Questions
What is the PECARN head injury decision rule?
The PECARN (Pediatric Emergency Care Applied Research Network) head injury prediction rule is an evidence-based clinical decision tool developed to identify children at very low risk for clinically important traumatic brain injury (ciTBI) after minor head trauma, thereby reducing unnecessary CT scans. Published by Kuppermann and colleagues in The Lancet in 2009, it was derived from the largest prospective pediatric head injury study ever conducted, enrolling over 42,000 children across 25 emergency departments in North America. The rule uses separate algorithms for children under 2 years and those aged 2 years and older, because the clinical predictors of brain injury differ between these age groups. The rule has been externally validated in multiple international studies with consistently high negative predictive value.
Why are there separate PECARN algorithms for children under 2 and over 2 years?
The PECARN study identified different clinical predictors of ciTBI for children under 2 years compared to those 2 years and older, necessitating separate algorithms. In children under 2, palpable skull fractures and non-frontal scalp hematomas are important predictors because infants have thinner, more deformable skulls and cannot verbalize symptoms like headache. The parent observation that the child is not acting normally carries significant weight in this age group because it serves as a proxy for altered mental status that cannot be reliably assessed in preverbal children. In children 2 years and older, clinical signs of basilar skull fracture, vomiting, and severe headache replace the infant-specific criteria because older children can communicate symptoms and their skull anatomy more closely resembles adults.
How accurate is the PECARN rule at identifying children who need CT scans?
The PECARN prediction rule demonstrates exceptional accuracy for identifying children at very low risk for ciTBI. In the validation cohort, the rule had a sensitivity of 100 percent for ciTBI in children under 2 years and 96.8 percent in children 2 years and older, meaning it correctly identified virtually all children with clinically significant brain injuries. The negative predictive value exceeds 99.95 percent for children classified as very low risk. If applied consistently, the PECARN rule could potentially reduce CT use by 20 to 25 percent in children presenting with minor head trauma. The very high sensitivity comes at the cost of moderate specificity (approximately 50 to 60 percent), meaning that many children classified as intermediate or high risk will not have ciTBI, but the rule reliably identifies who does NOT need imaging.
What constitutes a severe mechanism of injury in the PECARN criteria?
The PECARN rule defines severe mechanism of injury as motor vehicle crash with patient ejection, death of another passenger in the same vehicle, or rollover. For pedestrians or cyclists, severe mechanism includes being struck by a motor vehicle without a helmet. Falls are classified as severe if the distance exceeds 5 feet for children 2 years and older, or exceeds 3 feet for children under 2 years. Head struck by a high-impact projectile is also considered severe. Notably, common mechanisms such as ground-level falls, falls from beds or couches (typically less than 3 feet), walking into objects, and being struck by soft objects are NOT considered severe mechanisms. The mechanism of injury serves as an intermediate-risk predictor in both age-group algorithms and helps guide the observation versus CT decision.
What are the limitations of the PECARN head injury prediction rule?
The PECARN rule has several important limitations that clinicians should understand. First, it was designed only for minor head trauma with initial GCS of 14 or 15 and should not be applied to children with GCS less than 14, penetrating injuries, or known bleeding disorders. Second, the rule was validated primarily in North American emergency departments and may perform differently in other healthcare settings or populations. Third, the intermediate-risk category includes a wide range of ciTBI probabilities (0.8 to 0.9 percent), and clinical judgment remains essential for deciding between observation and CT in these patients. Fourth, the rule does not account for non-accidental trauma (child abuse), which requires a different diagnostic approach. Finally, the rule addresses only ciTBI and may miss isolated skull fractures or minor intracranial findings that, while not requiring intervention, may be clinically relevant in certain contexts.
How accurate are the results from Pecarn Head Ct Calculator?
All calculations use established mathematical formulas and are performed with high-precision arithmetic. Results are accurate to the precision shown. For critical decisions in finance, medicine, or engineering, always verify results with a qualified professional.