• Rakuhei Nakama, Ryo Yamamoto, Yoshimitsu Izawa, Keiichi Tanimura, and Takashi Mato.
• Department of Emergency Medicine, Saiseikai Utsunomiya Hospital, 911-1 Takebayashi-machi, Utsunomiya, Tochigi, 321-0974, Japan. r.n.emergency0611@gmail.com.
• Scand J Trauma Resus. 2021 Jan 7; 29 (1): 12.

BackgroundUnnecessary whole-body computed tomography (CT) may lead to excess radiation exposure. Serum D-dimer levels have been reported to correlate with injury severity. We examined the predictive value of serum D-dimer level for identifying patients with isolated injury that can be diagnosed with selected-region CT rather than whole-body CT.MethodsThis single-center retrospective cohort study included patients with blunt trauma (2014-2017). We included patients whose serum D-dimer levels were measured before they underwent whole-body CT. "Isolated" injury was defined as injury with Abbreviated Injury Scale (AIS) score ≤ 5 to any of five regions of interest or with AIS score ≤ 1 to other regions, as revealed by a CT scan. A receiver operating characteristic curve (ROC) was drawn for D-dimer levels corresponding to isolated injury; the area under the ROC (AUROC) was evaluated. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated for several candidate cut-off values for serum D-dimer levels.ResultsIsolated injury was detected in 212 patients. AUROC was 0.861 (95% confidence interval [CI]: 0.815-0.907) for isolated injury prediction. Serum D-dimer level ≤ 2.5 μg/mL was an optimal cutoff value for predicting isolated injury with high specificity (100.0%) and positive predictive value (100.0%). Approximately 30% of patients had serum D-dimer levels below this cutoff value.ConclusionD-dimer level ≤ 2.5 μg/mL had high specificity and high positive predictive value in cases of isolated injury, which could be diagnosed with selected-region CT, reducing exposure to radiation associated with whole-body CT.

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