Low plasma D-dimer concentration predicts the absence of traumatic brain injury in children.

BACKGROUND: Head Computerized Tomography (CT) has significant risks, especially in children. To reduce this burden, we sought to develop a biomarker panel that predicts the absence of traumatic brain injury (TBI) on head CT.

METHODS: We conducted a prospective cohort observational study followed by validation in a retrospective cohort at a regional pediatric trauma center. The prospective cohort included 57 consecutive children evaluated for TBI in the emergency department between September 2007 and March 2008. At the time of initial evaluation, blood was obtained to measure electrolytes, coagulation markers, complete blood count, and plasma levels of s100beta, D-dimer, and matrix metalloproteinase-9. We conducted routine statistical analysis to determine which predicted TBI on head CT. The independent retrospective cohort included 57 consecutive patients evaluated for the same indication.

RESULTS: All patients generally met common clinical criteria (such as the CHALICE criteria 4) for head CT after trauma. Plasma levels of D-dimer were associated with TBI on head CT by univariate analysis (p < 0.001). Other markers including prothrombin time, partial thromboplastin time, and s100beta were not. D-dimer also had the strongest association in multivariate analysis (p = 0.02). This association was independent of and stronger than the baseline Glascow Coma Scale (p = 0.08). A D-dimer level cut-off of 500 pg/microl had 94% negative predictive value (p < 0.001) for brain injury on head CT. The discriminatory capacity of this D-dimer level was confirmed in the independent retrospective cohort.

CONCLUSIONS: In children who meet clinical criteria for a head CT scan after trauma, low plasma d-dimer suggests the absence of significant brain injury.