Background: Current clinical decision rules to exclude deep vein thrombosis (DVT) are under-utilized partly because of their complexity.
Aims: To develop a new simple clinical decision rule to safely exclude DVT using D-dimer and Wells-rule items.
Methods: We used individual patient data from four prospective outpatient diagnostic DVT studies. A bootstrap approach with logistic regression was used to select Wells-rule items that would form the new clinical decision rule. Risk groups were then defined based on combinations of the selected items. D-dimer was applied with predetermined thresholds of < 500 ng/mL; 500 to 999 ng/mL; and ≥1,000 ng/mL to rule out DVT. DVT was considered safely excluded if the upper 95% confidence interval (CI) of DVT prevalence was < 2%.
Results: Four studies and 3368 patients were included in the analysis. Overall prevalence of DVT was 17%. In addition to D-dimer, ‘calf swelling > 3 cm’ and ‘DVT as the most likely diagnosis’ were included in the new rule. Based on these two variables, two clinical pre-test probability (CPTP) groups were defined; low (none of the two items present) and high (at least one of the items present). DVT can be safely excluded in patients with low CPTP with a D-dimer < 500 ng/mL (prevalence = 0.1%; 95% CI: 0.0-0.8%), low CPTP with a D-dimer between 500 ng/mL and 999 ng/mL (prevalence = 0.3%; 95% CI: 0.0-1.7%), and high CPTP with D-dimer < 500 ng/mL (prevalence = 0.3%; 95% CI: 0.0-1.0%).
Conclusions: We derived a simple clinical decision rule with 3 items as shown in Figure 1. The results suggest that the rule can safely exclude DVT. Prospective validation is required.
To cite this abstract in AMA style:Xu K, de Wit K, Geersing G-, Takada T, Schutgens R, Elf J, Kearon C, SP. A Simplified Decision Rule to Rule out Deep Vein Thrombosis Using Clinical Assessment and D-dimer [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/a-simplified-decision-rule-to-rule-out-deep-vein-thrombosis-using-clinical-assessment-and-d-dimer/. Accessed May 16, 2022.
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