VTE: Assessment of PTP

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

The diagnosis of venous thromboembolism (VTE) is based on assessment of the population pretest probability (PTP) of VTE. How to assess this probability?

Wendy Lim, MD, MSc: It is a good question. PTP is typically determined using clinical decision rules. These are typically rules that have been validated, ideally in a prospective population.

A good example for pulmonary embolism is the Wells score or the Geneva score. These scores look at signs and symptoms of pulmonary embolism, deep vein thrombosis, and risk factors for VTE. Each of these items is scored, and based on this score one can determine if a patient falls into a low, intermediate, or high pretest probability category.

Those are examples of clinical decision rules for pulmonary embolism. Likewise, there are also clinical decision rules for deep vein thrombosis of the lower and upper extremity as well.