D-Dimer Testing

D-dimer is a decision aid, not a clot locator. A raised result indicates active clot formation and breakdown somewhere in the body; it does not confirm venous thromboembolism (VTE) or identify its site. A negative result can exclude VTE only when the patient's pretest probability and the assay's validated threshold make that interpretation appropriate. Start with a validated clinical probability assessment such as Wells or revised Geneva. A patient with high or likely probability proceeds to imaging. A patient with low or intermediate probability may be eligible for exclusion with a negative high-sensitivity D-dimer. If a patient has low pretest probability for pulmonary embolism (PE) and meets every Pulmonary Embolism Rule-out Criteria (PERC) item, no D-dimer is required. Unnecessary testing can produce false-positive results and avoidable imaging. These rule-out strategies apply to the population in which the pathway was validated. The BC guideline applies its outpatient algorithm to hemodynamically stable adults and directs inpatients to imaging because D-dimer risk stratification has not been validated for them. Most studies of D-dimer rule-out strategies excluded patients already receiving anticoagulation, so do not...