Derivation and Validation of a Simple Model to Identify Venous Thromboembolism Risk in Medical Patients

Study Questions:

What is the minimum set of venous thromboembolism (VTE) risk factors most predictive of clinically overt VTE among hospitalized medical patients?


The authors reported an analysis of a retrospective cohort of medical admissions between January 1, 2000 and December 31, 2007, to Intermountain Healthcare–associated hospitals in Utah and southeastern Idaho. Using electronic medical record interrogation, they identified those subjects with objectively confirmed VTE during hospitalization or within 90 days following discharge. A risk assessment model was derived based on a stepwise forward logistic regression of various candidate factors. This risk assessment model was then applied to a validation cohort of medical admissions to the same hospitals between January 1, 2008 and December 31, 2009.


The authors reviewed electronic medical records for 143,000 subjects in the derivation cohort and 46,000 subjects in the validation cohort. They identified four risk factors: previous VTE; an order for bed rest; a peripherally inserted central venous catheter; and the diagnosis of cancer, as the minimal set most predictive of VTE (area under the receiver operating characteristic curve [AUC] = 0.874; 95% confidence interval [CI], 0.869-0.880). These four risk factors maintained predictive power in the validation cohort (AUC = 0.843; 95% CI, 0.833-0.852). This four-element risk assessment model had a performance superior to the Kucher score (AUC = 0.756).


The authors concluded that the four-element risk assessment model identified in this study may be used to identify patients at risk for VTE and improve rates of thromboprophylaxis. The authors further opined that this simple and accurate risk assessment model is an alternative to the more complicated published VTE risk assessment tools that currently exist.


The authors of this study have performed a great service by using the power of a large clinical database to cleanly identify four clinical risk factors, which combine to create a risk assessment model having a very strong association with the development of VTE. The use of an electronic medical record as the data source should carry with it the usual potential limitations about the accuracy of clinical diagnoses and the use of ICD-9 diagnosis codes. Furthermore, the authors point out that appropriate use of thromboprophylaxis may have reduced the rate of VTE observed, possibly disproportionately so. Nonetheless, the large number of subjects studied, the methodological rigor of the analysis, and the use of clinical data, strongly support the validity of the current study. A simple four-element risk assessment model is a very welcome addition to the currently published risk assessment models, which are quite cumbersome and complex. This new model requires prospective validation, but promises to be a very useful clinical tool to identify those hospitalized medical patients who warrant thromboprophylaxis.

Clinical Topics: Invasive Cardiovascular Angiography and Intervention, Pulmonary Hypertension and Venous Thromboembolism, Vascular Medicine, Interventions and Vascular Medicine

Keywords: Hospitals, Utah, Catheterization, Peripheral, Central Venous Catheters, Venous Thromboembolism, Cardiovascular Diseases, Risk Factors, Idaho, Risk Assessment

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