Deep vein thrombosis: magnetic resonance venography excluded it.

Clinical bottom line (level 2b)

  1. In patients with suspected deep vein thrombosis, a positive magnetic resonance venography made it much more likely (LR+25)
  2. A negative MR scan excluded venous thrombosis, (LR- = 0} although upper 95%CI was 0.11.
Carpenter et al: Journal of vascular Surgery 1993; 18: 734-741
Expires May 2003

The study

Setting: university hospital and Veterans' Affairs centre, USA

85 patients (aged ?, ?% male) suspected deep vein thrombosis

Independent blinded reference standard, applied in all patients from a consecutive ?appropriate spectrum.
Reference standard:
  • contrast venography
Diagnostic test: magnetic resonance venography (from inferior vena cava to popliteal veins): on average taking 50 minutes; positive if central signal void with hyperintense signal or no flow in vessel ± intraluminal thrombus

The evidence

pre-test probability of deep vein thrombosis: 27%, (95% CI: 18% to 35%)

diagnostic test DVT no DVT LR+
(95% CI)		 post-test probability LR-
(95% CI)		 post-test probability
magnetic resonance venography 27 3 25
(8.1 to 75) 		90% 0.0
(0.0 to 0.11) 		0%
total 27 74

Comments

  1. MRI is more expensive and time consuming than other non-invasive studies. No clear role for it currently.
  2. No further studies have validated these results

Citation

  1. Carpenter JP, Holland GA, Baum RA, et al: Magnetic resonance venography for the detection of deep venous thrombosis: comparison with contrast venography and Duplex ultrasound. Journal of vascular Surgery 1993; 18: 734-741
Contributor: Chris Ball and Clare Wotton, May 2000
Reviewer: Alex Gallus

Clinical Question.
Patient suspected DVT
Intervention or Exposure magnetic resonance venography
Comparison contrast venography
Outcome diagnosis