Minimum Age for Ottawa CT Head Rules
The Ottawa CT Head Rule is validated for adults aged 16 years and older and should not be applied to pediatric patients below this age threshold. 1, 2
Age Specifications and Validation
The Ottawa CT Head Rule was specifically developed and validated for patients aged 16 years and older presenting with minor head injury (Glasgow Coma Scale 13-15). 1, 3 The original derivation study included 3,121 adult patients with a mean age of 38.7 years, and the inclusion criteria explicitly required age 16 years or greater. 3, 4
Key exclusion criterion: Age less than 16 years is an absolute contraindication to applying the Ottawa CT Head Rule. 1
Why Pediatric Patients Are Excluded
Children require different clinical decision rules because:
Pediatric-specific anatomy and injury patterns differ fundamentally from adults, necessitating separate validation studies and decision rules. 5
The CATCH (Canadian Assessment of Tomography for Childhood Head injury) rule was specifically developed for children, derived from 3,866 pediatric patients with mean age 9.2 years. 6
The PECARN (Pediatric Emergency Care Applied Research Network) rule provides validated criteria for children under 2 years of age, with 100% sensitivity and negative predictive value when specific low-risk criteria are met. 5
Comparison with Other Anatomic Decision Rules
For context, other Ottawa rules have different pediatric age thresholds:
Ottawa Ankle and Foot Rules are validated for children older than 5 years of age, demonstrating that each anatomic region requires separate pediatric validation. 1
Ottawa Knee Rule applies to patients 18 years of age or older, with the Pittsburgh Decision Rule covering patients younger than 12 years or older than 50 years. 1
Critical Clinical Pitfall
Do not attempt to apply the Ottawa CT Head Rule to pediatric patients under 16 years. 1 Instead, use validated pediatric-specific decision rules:
For children ≥2 years: Use PECARN or CATCH rules, which identify high-risk factors including GCS <15 at 2 hours, signs of basilar skull fracture, altered mental status, and severe mechanism of injury. 5, 6
**For children <2 years: Use PECARN criteria**, which include palpable skull fracture, altered mental status, scalp hematoma, loss of consciousness >5 seconds, severe mechanism of injury, and parental concern about abnormal behavior. 5
Adult Application (≥16 Years)
Once the patient meets the minimum age of 16 years, the Ottawa CT Head Rule demonstrates:
100% sensitivity for detecting need for neurosurgical intervention when high-risk factors are present (GCS <15 at 2 hours, suspected skull fracture, basilar skull fracture signs, vomiting ≥2 episodes, age ≥65 years). 3, 7
98.4% sensitivity for clinically important brain injury when medium-risk factors are included (amnesia >30 minutes before impact, dangerous mechanism of injury). 3
Superior specificity (50.6%-76.3%) compared to New Orleans Criteria (12.1%-12.7%), potentially reducing CT utilization by 37% while maintaining safety. 7, 8