In suspected deep vein thrombosis, which test is most sensitive and used as first-line diagnostic test?

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When evaluating suspected deep vein thrombosis, you want a test that reliably detects clot while being practical to perform right away. Compression ultrasonography fits this best because it is noninvasive, readily available at the bedside, and highly accurate for proximal DVT (about 95% sensitivity with high specificity). This makes it the most suitable first-line imaging test to confirm or exclude DVT in most patients.

D-dimer is extremely sensitive but not specific; a positive result can occur with many conditions, and a negative result only helps rule out DVT in patients with low pretest probability. Venography is invasive and rarely used as a first-line test, while MR venography, though informative, is less accessible and more costly. So compression ultrasonography provides the best balance of sensitivity, practicality, and safety for initial evaluation. If suspicion remains high despite a negative ultrasound, additional imaging or repeat testing may be considered.