D-dimer testing is most useful for which scenario in suspected DVT?

• A. For high-risk suspected DVT
• B. To diagnose DVT directly
• C. For low-risk suspected DVT
• D. To monitor therapy only

Answer: (C)

D-dimer is most helpful as a rule-out test in patients with low pretest probability of DVT. It is highly sensitive but not specific, so a negative result in someone with low clinical suspicion essentially excludes DVT, allowing you to avoid imaging. In those with high pretest probability, a negative D-dimer doesn’t reliably rule out DVT, so imaging (like compression ultrasound) is still needed. D-dimer isn’t used to diagnose DVT directly, since a positive result can occur with many other conditions (inflammation, cancer, recent surgery, pregnancy, aging, etc.), and it isn’t a reliable way to monitor therapy.