The Oudega clinical decision rule for suspected DVT was specifically developed for use in primary care. The rule incorperates D-dimer testing into the rule. A score between 0 and 3 implicates a very low score, with a subsequent DVT risk of 0.7%. In a validation study, this DVT risk was 1.4% (95% CI 0.6% to 2.9%) enabling an exclusion of DVT in about 50% of all suspected patients.
Although the rule incorperates D-dimer testing, in essence D-dimer testing is not necessary if the score is already above 3 point based on the clinical items only: in that specific situation, the risk of DVT will be above 2% already and thus referral to secondary care is needed, regardless of the results of D-dimer testing. Hence, the guideline for Dutch GPs recommends to first score the clinical items, and only perform D-dimer testing if the score based on the clinical items is between 0 and 3. In addition, referral is needed for all patients if the score on the clinical items is 4 or more.