D-dimer as the first choice test to confirm an episode of VTE

Dr Wendy Lim is a professor in the Division of Hematology and Thromboembolism at McMaster University.

Despite guidelines and educational campaigns, preliminary results of a survey among Polish physicians show that many of them still consider the D-dimer test as the first choice to confirm an episode of venous thromboembolism (VTE). Could you comment on the value of the pretest probability evaluation before choosing an appropriate test?

Wendy Lim, MD, MSc: I would say that most patients who have suspected pulmonary embolism (PE) in fact do not have PE. Most patients, if we apply a clinical decision rule, actually do fall into that low clinical pretest probability category. In that case, in fact, choosing the D-dimer [test] is appropriate because that is where most patients will be.

In many situations, a lot of clinicians do not formally use a clinical decision rule to assess pretest probability. They assess the patient through a combination of methods, they have a sense: “Do I think this patient actually has VTE or not?” The clinical decision rules really just formalize that process and help to streamline the testing so [that] it is a bit more appropriate.