Deep vein thrombosis: impedance plethysmography was less effective than initially thought.

Clinical bottom line (level 4)

  1. Impedance plethysmography may rule out deep vein thrombosis in low risk patients and diagnose it in high risk patients, but confirmatory testing is otherwise required.
Anderson et al: Annals of Internal Medicine 1993; 118 (1): 25-30
Expires May 2003

The study

Setting: teaching hospital, Canada

384 patients (aged mean 61 years, 58% female) clinically suspected first episode of deep vein thrombosis

Excluded if
  • technically inadequate impedance plethysmography



    • Independent unblinded reference standard, applied in all patients from a consecutive ?appropriate spectrum.
    Reference standard:
    • venography or failed to return with new symptoms
    Diagnostic test: impedance plethysmography
    • Patient data was found in a retrospective chart review.

    The evidence

    pre-test probability of deep vein thrombosis: 15%, (95% CI: 11% to 18%)

    diagnostic test DVT no DVT LR+
    (95% CI)    		 post-test probability LR-
    (95% CI)    		 post-test probability
    impedance plethysmography 37 20 11
    (6.8 to 17)     		65% 0.36
    (0.25 to 0.52)     		6%
    total 56 328

    Comments

    1. Results are similar to a study by Ginsberg et al, 1993.
    2. Impedance plethysmography is rarely used in clinical practice, and requires specialised equipment and operators

    Citation

    1. Anderson DR, Lensing AWA, Wells PS, et al: Limitations of impedance plethysmography in the diagnosis of clinically suspected deep-vein thrombosis. Annals of Internal Medicine 1993; 118 (1): 25-30
    Search Terms: hand search
    Contributor: Chris Ball and Clare Wotton, May 2000
    Reviewer: Alex Gallus

    Clinical Question.
    Patient DVT
    Intervention or Exposure impedance plethysmography
    Comparison venography
    Outcome diagnosis