Deep vein thrombosis: a normal d-dimer can rule it out in low-risk patients

Clinical bottom line (level 1b)

  1. Patients with a suspected DVT with a normal whole blood agglutination d-dimer were less likely to have one (LR - 0.11) .
  2. Patients considered to be low risk for a DVT with a normal d-dimer had a 1% chance of having one.
Lennox et al: Journal of Vascular Surgery 1999; 30 : 794-804
Expires November 2003

The study

Setting: university hospital, UK

200 patients (aged 18 to 91; mean 58, 63% female) with a clinically suspected DVT referred for an ultrasound scan. Patients were stratified for risk of DVT using a validated clinical prediction guide.

Excluded if
  • previously diagnosed DVT
  • features of chronic DVT on ultrasound scan
  • symptoms lasting 1 month or more
  • therapeutic anticoagulation for > 48 hours
  • clinically suspected or confirmed pulmonary embolism with ultrasound scan performed to excluded lower limb DVT


    Independent blinded reference standard, applied in all patients from a consecutive appropriate spectrum.
    Reference standard:
    • duplex ultrasound scan
    Diagnostic test: whole blood agglutination d-dimer (SimpliRED)

    The evidence

    pre-test probability of DVT: 23%, (95% CI: 17% to 29%)

    diagnostic test DVT no DVT LR+
    (95% CI)    		 post-test probability LR-
    (95% CI)    		 post-test probability
    d-dimer 42 28 5.0
    (3.6 to 7.1)     		60% 0.11
    (0.042 to 0.27)     		3%
    total 46 157


    diagnostic test DVT no DVT LR+
    (95% CI)    		 post-test probability LR-
    (95% CI)    		 post-test probability
    low-risk: d-dimer 3 8 7.9
    (3.3 to 19)     		27% 0.28
    (0.051 to 1.51)     		1%
    total 4 84


    diagnostic test DVT no DVT LR+
    (95% CI)    		 post-test probability LR-
    (95% CI)    		 post-test probability
    moderate risk: d-dimer 9 12 3.4
    (1.9 to 6.3)     		43% 0.32
    (0.12 to 0.86)     		7%
    total 12 55


    diagnostic test DVT no DVT LR+
    (95% CI)    		 post-test probability LR-
    (95% CI)    		 post-test probability
    high risk: d-dimer 30 8 1.9
    (1.2 to 3.0)     		79% 0.0
    (0.0 to 0.20)     		0%
    total 30 15

    Comments

    1. The study has too few patients to generate narrow confidence intervals for the different risk groups. However it does demonstrate that the likelihood ratios remain approximately the same for all three groups.

    Citation

    1. Lennox AF, Delis KT, Serunkuma S, et al: combination of a clinical risk assessment score and rapid whole blood D-dimer testing in the diagnosis of deep vein thrombosis in symptomatic patients. Journal of Vascular Surgery 1999; 30 : 794-804
    Search Terms: from ACP Journal Club other articles noted
    Contributor: Chris Ball, November 2001
    Reviewer:

    Clinical Question.
    Patient suspected DVT
    Intervention or Exposure d-dimer and clinical prediction guide
    Outcome deep vein thrombosis
    		•