Assessment of ICD-9-CM Codes included in the CDC's Definition of a Traumatic Brain Injury

Introduction:This study evaluated the sensitivity and specificity of CDC’s TBI ICD-9-CM code-based definition to detect TBI in a pediatric population.

Methods:We reviewed 200 pediatric medical records from patients who sustained a suspected TBI from April – September 2013 for “signs and symptoms” consistent with CDC’s TBI clinical definition (Marr et al 2002). Patients with a suspected head injury were randomly sampled from a system of Emergency Departments (EDs) (n = 150) and a concussion services clinic (n = 50). ICD-9-CM diagnosis data was obtained from each billing department. Sensitivity and specificity of ICD-9-CM codes to detect TBI was calculated.

Results:‘Head Injury, Unspecified’ was the most commonly reported (19%) ICD-9-CM code among sampled ED patients. ‘Intracranial Injury’ (37%) and ‘Lack of Coordination’ (37%) were the most commonly reported ICD-9-CM codes among sampled concussion services patients. Sensitivity (66%; 95% CI = 57%-74%) and specificity (63%; 95% CI = 51%-74%) of CDC’s definition was relatively low. Among charts with a single reported ICD-9-CM code, ‘Intracranial Injury’ had the highest positive predictive value (PPV) (100%) and ‘Head Injury, Unspecified’ had the lowest PPV (42%). Among charts with multiple codes, PPV was highest when a CDC TBI code and TBI sign/symptom code (89%) were present.

Conclusion:Sensitivity and specificity of CDC’s TBI definition could be improved if TBI sign/symptom codes are included when in conjunction with other TBI-related codes.  Further research is needed to determine if combinations of ICD-9-CM codes would increase the sensitivity without negatively impacting specificity.