Deep vein thrombosis: serial ultrasound helped diagnosis.

Clinical bottom line (level 1b)

  1. A sixth of patients with suspected deep vein thrombosis had it.
  2. In patients with suspected deep vein thrombosis, a positive serial compression ultrasound made it much more likely (LR+150) , and a negative one makes it less likely (LR-0.10) .
  3. <1% of patients with two negative ultrasounds had a DVT.
  4. Witholding anticogulation between negative ultrasounds was safe
Birdwell et al: Annals of Internal Medicine 1998; 128 (1): 1-7
Expires May 2003

The study

Setting: teaching hospital, USA

405 patients (aged range 19 to 98 years; mean 53, 67% female) suspected first episode of deep vein thrombosis

Excluded if
  • compression ultrasound not possible
  • unable to return for repeat scan in 5-7 days
  • no long term follow-up possible
  • received therapeutic dose of heparin >24 hours
  • pregnant



    • Independent blinded reference standard, applied in all patients from a consecutive appropriate spectrum.
    Reference standard:
    • venography or follow-up for three months. During follow-up, DVT was diagnosed by serial impedance plethysmography and if abnormal, confirmed by venography. Pulmonary embolism diagnosed by high-probabolity ventilation-perfusion scan
    Diagnostic test: compression ultrasound; if positive had venogram, if negative had repeat venogram in 5-7 days , and anticoagulation withheld in the meantime

    The evidence

    pre-test probability of deep vein thrombosis: 17%, (95% CI: 14% to 21%)

    diagnostic test DVT no DVT LR+
    (95% CI)    		 post-test probability LR-
    (95% CI)    		 post-test probability
    serial ultrasound scan 63 2 150
    (38 to 600)     		97% 0.10
    (0.05 to 0.20)     		2%
    total 70 335

    • Repeat testing was carried outin 91% of patients- seven additional DVTs were detected.
    • 2/335 patients with negative serial ultrasound scans had DVT (0.6%: 95% CI: 0.04% to 2.1%).

    Comments

    1. Rule was not tested in patients with suspected PE

    Citation

    1. Birdwell BG, Raskob GE, Whitsett TL, et al: The clinical validity of normal compression ultrasonoraphy in outpatients suspected of having deep venous thrombosis. Annals of Internal Medicine 1998; 128 (1): 1-7
    Contributor: Chris Ball and Clare Wotton, May 2000
    Reviewer: Alex Gallus

    Clinical Question.
    Patient suspected DVT
    Intervention or Exposure compression ultrasound
    Comparison venography
    Outcome diagnosis