Background

Abusive head trauma is the leading cause of death from child abuse and the leading cause of death from traumatic brain injury. Identification of clinically important traumatic brain injury is essential. The PECARN head trauma rule for children less than 2 years of age includes 6 predictors (PECARN 2009). The predictors of “acting normally as per parents” and “a high-risk mechanism of injury” may be unreliable in infants with abusive head trauma. Because symptoms of abusive head trauma are non-specific, a high percentage of patients are seen by physicians prior to a definitive diagnosis. The Pittsburgh Infant Brain Injury Score was retrospectively derived from 187 infants (37 with abusive head trauma) who presented to a single tertiary care children’s hospital. Five predictor

variables were identified: age ≥ 3 months, head circumference percentile > 90th percentile, a serum hemoglobin <11.2 g/dl, an abnormality on neurologic or dermatologic examination, and a previous emergency department (ED) visit for a high- risk symptom. The receiver operator characteristic (ROC) curve had an area under the curve of 0.87, 95% CI (0.80, 0.95). 

The current study was designed to validate and refine the Pittsburgh Infant Brain Injury Score (PIBIS) clinical prediction rules. Two previous parameters (previous ED visit for a high-risk symptom and an abnormal neurological exam) were not included in the new rule. In addition, the cutoff for head circumference was decreased from >90% to > 85%.

Clinical Question

In pediatric patients between 1-12 months of age who present to the ED without a history of trauma but with symptoms associated with an increased risk of abusive head trauma do the clinical predictors included in the new revised Pittsburgh Infant Brain Injury Score accurately identify patients with and without abusive head trauma?

Population

30-364 days of age, well-appearing, temperature <38.3°C, without a history of trauma, presenting for a symptom that is associated with an increased risk of abusive head trauma: ALTE, apnea, vomiting without diarrhea, seizure/seizure like activity, soft tissue swelling of the scalp, bruising, lethargy, fussiness, poor feeding

Intervention

Rule Parameters:
Clinical and lab parameters collected on a standardized data collection instrument included HPI, PMH, history of previous ED visits, results of lab/radiologic testing, neurological and dermatologic exam findings, serum Hgb, head circumference, and discharge diagnoses. Socioeconomic status or social history were not collected.

Reference Standard/Control:
1. Imaging: CT or MRI was ordered at discretion of treating physician. Images were interpreted as part of clinical care and by a neuroradiologist. When there was a difference between interpretations, a pediatric neurosurgeon reviewed the images and a consensus was reached (ie; normal, equivocal, or abnormal)
2. Cases/Controls: Subjects were classified as cases or controls. Cases were determined by abnormal neuroimaging at enrollment or during follow-up (further classified into possible traumatic, probable/definite traumatic, and atraumatic), while controls had normal or no neuroimaging at enrollment or during follow-up. Subjects were tracked by medical record review for 6 months after enrollment or up to 1 year of age (whichever came later) to identify subjects with abnormal neuroimaging during the follow-up period and/or those who had neuroimaging performed to follow up on symptoms at enrollment.
3. Abusive head trauma: diagnosis was defined as a brain injury that was assessed by each site’s hospital-based Child Protection Team (CPT) as being due to definite or probable, but not possible, abuse.

Outcomes

Rule characteristics: new derivation set (modified from original)
Area under the receiver operating characteristic curve (ROC)

Design

Prospective, multicenter (3 children’s hospitals) validation study

Excluded

Previous abnormal head CT

Primary Results

  • N = 1,040 enrolled (801 at primary center)
  • 862 with complete data (all 4 rule characteristics)
  • Mean age was 4.7 (52% boys)
  • Case: 214 (21%), Neuroimaging 213 (99.5%), 0.5% follow up
  • Control: 826 (79%), Neuroimaging 507 (61%)
PITTSBURGH INFANT BRAIN INJURY SCORE POINTS
Abnormal Dermatologic Examination 2
Age ≥3.0 months 1
Head circumference >85th percentile 1
Serum hemoglobin <11.2 g/dL 1

Rule Characteristics Results (based on 862 with complete data)

  • Area under the Receiver Operating Curve Characteristic Curve
    0.83, 95% CI (0.80, 0.86)
IDENTIFICATION OF ABNORMAL IMAGING
(95% Confidence Intervals)
Sensitivity (Identifying abnormal imaging at a score of 2) 93% (89%-96%)
Specificity (Identifying abnormal imaging at a score of 2) 53%  (49%-57%)
Negative Predictive Value (Score <2) 96% (93.6%-97.9%)
Positive Predictive Value (Score ≥2) 39% (34.8 %-43.6%)
LR of a positive rule 1.9
LR of a negative rule 0.13

Strengths

  • Large, prospective, multicenter study asking a patient centered question

  • 83% of the patients enrolled had complete data on all 4 clinical decision rule variables

  • There was no difference between the sites in terms of proportions of patients with complete data.

Limitations

  • Convenience sample, which could lead to selection bias. During the study period other children with similar symptoms were evaluated in the study EDs but were not approached for enrollment

  • Not all subjects had imaging, allowing some cases to possibly be misclassified as controls

Author's Conclusions

"Our data suggest that the PIBIS accurately identifies infants who would benefit from neuroimaging to evaluate for brain injury. An implementation analysis is needed before the PIBIS can be integrated into clinical practice.”

Our Conclusions

This study is described as a validation of a previously derived decision rule but is in fact a re-derivation of the rule. Two previous parameters, previous ED visit for a high-risk system and neurologic exam were excluded from the rule. In addition, the cutoff for head circumference was decreased from > 90% to > 85%. An internal validation analysis was not included. This is a level IV rule. It is a rule that has been derived only or validated only in split samples, large retrospective databases or by statistical methods. A level IV rule requires further validation before it can be applied clinically. Several limitations need to be addressed before it can be adopted clinically.

Potential Impact To Current Practice

The concept that nonspecific symptoms in an infant can be due to abusive head trauma is important to remember. This study represents a first step in the development of a decision rule to identify infants without a history of head trauma but with symptoms that may be related to head trauma who are likely to have abnormal imaging. The potential benefit of a validated rule that demonstrated impact would be to target head CT use to those at highest risk limiting unnecessary head CT’s and reducing radiation exposure.

Bottom Line

It is essential to remember that the Pittsburgh Infant Brain Injury Score was designed to be used in well-appearing infants in whom brain injury may not be part of the initial differential diagnosis. The rule is not generalizable to patients in which there is a high suspicion of non-accidental trauma. In addition, the predictor “abnormal dermatologic exam” is somewhat subjective and no measure of inter-rater reliability was presented.

Read More

References

Kupperman N et al. Identification of children at very low risk of clinically-important brain injures after head trauma: a prospective cohort study. Lancet 2009; 374(9696): 1160-70. PMID: 19758692