Evaluation of a D-Dimer Protocol for Detection of Venous Thromboembolism

The use of venous duplex ultrasonography (VDU) for confirmation of deep venous thrombosis in neurosurgical patients is costly and requires experienced personnel. We evaluated a protocol using D-dimer levels to screen for venous thromboembolism (VTE), defined as deep venous thrombosis and asymptomatic pulmonary embolism.

We used a retrospective bioinformatics analysis to identify neurosurgical inpatients who had undergone a protocol assessing the serum D-dimer levels and had undergone a VDU study to evaluate for the presence of VTE from March 2008 through July 2017. The clinical risk factors and D-dimer levels were evaluated for the prediction of VTE.

In the 1918 patient encounters identified, the overall VTE detection rate was 28.7%. Using a receiver operating characteristic curve, an area under the curve of 0.58 was identified for all D-dimer values (P = 0.0001). A D-dimer level of ≥2.5 μg/mL on admission conferred a 30% greater relative risk of VTE (sensitivity, 0.43; specificity, 0.67; positive predictive value, 0.27; negative predictive value, 0.8). A D-dimer value of ≥3.5 μg/mL during hospitalization yielded a 28% greater relative risk of VTE (sensitivity, 0.73; specificity, 0.32; positive predictive value, 0.24; negative predictive value, 0.81). Multivariable logistic regression showed that age, male sex, length of stay, tumor or other neurological disease diagnosis, and D-dimer level ≥3.5 μg/mL during hospitalization were independent predictors of VTE.

The D-dimer protocol was beneficial in identifying VTE in a heterogeneous group of neurosurgical patients by prompting VDU evaluation for patients with a D-dimer values of ≥3.5 μg/mL during hospitalization. Refinement of this screening model is necessary to improve the identification of VTE in a practical and cost-effective manner.