D-Dimer for suspected DVTEvaluation of D-Dimer in the Diagnosis of Suspected Deep-Vein Thrombosis.
Wells PS, Anderson DR, Rodger M, Forgie M, Kearon C, Dreyer J, Kovacs G, Mitchell M, Lewandowski B, Kovacs MJ
N Engl J Med 2003 Sep 25;349(13):1227-1235.
abstract (from PubMed)
This study looked at the ability of a D-dimer assay used together with clinical probability to safely reduce the number of outpatients with suspected DVT requiring duplex ultrasound examination. Patients were randomized to either a "no D-dimer, all ultrasound" strategy, or to a "D-dimer, selective ultrasound strategy". Using a clinical scoring system, patients were first assigned a low or a high probability of having a DVT.
In the group of patients with a clinically low probability of DVT, those randomized to the all-ultrasound strategy underwent a single ultrasound examination. Patients randomized to the selective ultrasound strategy underwent an ultrasound examination only if the D-dimer was positive.
In the group of patients with a clinically high probability of DVT, those randomized to the all-ultrasound strategy underwent an ultrasound examination, with a second examination a week later if the first was negative. Those randomized to the selective strategy also all underwent a first duplex ultrasound, but underwent the second examination only if the D-dimer was positive.
- Safety of the approach
601 patients were deemed to be clinically low-probability. Among patients randomized to the selective strategy, with negative ultrasound results, there were 2 venous thromboembolic events during three month follow-up. Among patients randomized to the all-ultrasound approach with negative results, there were 4 events (NS).
495 patients were deemed to be clinically high-probability. The corresponding numbers of patients with negative ultrasound examinations and follow-up events were 0 for the selective strategy and 2 for the all-ultrasound strategy.
- Reduction in ultrasound examinations
The percentage of patients requiring an ultrasound examination in the low-probability group was 31% for the selective strategy and 100% for the all-ultrasound strategy. In the high probability group, all patients underwent the first ultrasound examination, but only 55% underwent the second examination in the selective group, as opposed to all in the other group.
The authors conclude that this approach, combining D-dimer assay with a clinical assessment is safe, and allows a reduction in the number of ultrasound examinations required.
Using a clinical scoring systemSeptember 25, 2003
The applicability of this study depends on classifying patients into low-risk and high-risk groups the same way the authors did. They use a scoring system which takes into account a number of risk factors, including prior DVT, edema, pain along the trajectory of a vein, active cancer. If this particular scoring system is not used when applying these results to the "real world", they may not be valid.
Studies with clinical scoring systems always make me wonder how many practicing physicians actually remember and apply them. Maybe with the increasing use of handhelds this will become easier?
posted on 2003-09-25 13:05:44 by
Michael Jacobson, MD, MPH
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