Update of the CHIP (CT in Head Injury Patients) decision rule for patients with minor head injury based on a multicenter consecutive case series

OBJECTIVE: To update the existing CHIP (CT in Head Injury Patients) decision rule for detection of (intra)cranial findings in adult patients following minor head injury (MHI).METHODS: The study is a prospective multicenter cohort study in the Netherlands. Consecutive MHI patients of 16 years and older were included. Primary outcome was any (intra)cranial traumatic finding on computed tomography (CT). Secondary outcomes were any potential neurosurgical lesion and neurosurgical intervention. The CHIP model was validated and subsequently updated and revised. Diagnostic performance was assessed by calculating the c-statistic.RESULTS: Among 4557 included patients 3742 received a CT (82%). In 383 patients (8.4%) a traumatic finding was present on CT. A potential neurosurgical lesion was found in 73 patients (1.6%) with 26 (0.6%) patients that actually had neurosurgery or died as a result of traumatic brain injury. The original CHIP underestimated the risk of traumatic (intra)cranial findings in low-predicted-risk groups, while in high-predicted-risk groups the risk was overestimated. The c-statistic of the original CHIP model was 0.72 (95% CI 0.69-0.74) and it would have missed two potential neurosurgical lesions and one patient that underwent neurosurgery. The updated model performed similar to the original model regarding traumatic (intra)cranial findings (c-statistic 0.77 95% CI 0.74-0.79, after crossvalidation c-statistic 0.73). The updated CHIP had the same CT rate as the original CHIP (75%) and a similar sensitivity (92 versus 93%) and specificity (both 27%) for any traumatic (intra)cranial finding. However, the updated CHIP would not have missed any (potential) neurosurgical lesions and had a higher sensitivity for (potential) neurosurgical lesions or death as a result of traumatic brain injury (100% versus 96%).CONCLUSIONS: Use of the updated CHIP decision rule is a good alternative to current decision rules for patients with MHI. In contrast to the original CHIP the update identified all patients with (potential) neurosurgical lesions without increasing CT rate.