Diagnostic classification in patients with deep venous thrombosis

I enjoyed and learned from the paper in the October issue comparing GPs' judgement with the Oudega decision rule for referring patients with suspected deep venous thrombosis for ultrasonography.1 One technical point about the Oudega rule variables puzzles me (see Table 1). The caption to the Table states, ‘The score could range from 0 to 14…’. The heaviest weightings are given to abnormal D-dimer results (6 points) and calf swelling ≥3 cm (2 points). The six remaining variables are weighted as one point each. Scoring on all eight variables indeed produces a score of 14, but to do so a patient would need to be of male sex and also use oral contraceptives.

Perhaps the range of the Oudega rule should be stated as 0 to 13, with one point scored for male sex OR oral contraceptive use.

• © British Journal of General Practice, 2011