Deep vein thrombosis: a clinical prediction rule and investigation strategy can accurately diagnose DVT.

Clinical bottom line (level 1a)

  1. A clinical prediction rule can accurately rank patients as high, moderate or low risk of deep vein thrombosis.
  2. Using this management strategy, combined with impedance plethysmography, only 1% of deep vein thomboses are missed.
Wells et al: Journal of Internal Medicine 1998; 243: 15-23
Expires May 2004

The study

Setting: three teaching hospitals, Canada and Italy

593 patients (aged mean 57 years, 58% female) outpatients with suspected deep venous thrombosis

Excluded if
  • <18 years old
  • previous objectively documented DVT or pulmonary embolism
  • signs or symptoms of current pulmonary embolism
  • anticoagulation treatment for more than 24 hours
  • patient could not be followed up
  • pregnant
  • contraindication to contrast media
  • below knee amputation



    • Independent blinded reference standard, applied in all patients from a consecutive appropriate spectrum.
    Reference standard:
    • venogram and follow-up for 6 months
    Diagnostic test: (1) clinical prediction rule used to rank patients into high, moderate or low risk for deep venous thrombosis:
    • active cancer (on-going treatment or diagnosed within 6 months or palliative care)- score 1
    • paresis, paralysis or recent plaster cast immobilisation of lower extremity- score 1
    • recently bedridden for more than 3 days and/or major surgery within 4 weeks- score 1
    • localised tenderness over distribution of deep veins- score1
    • entire leg swollen- score1
    • calf swelling more than 3 cm compared with asymptomatic side, measured at 10 cm below tibial tubercle- score 1
    • pitting oedema (greater in symptomatic leg)- score 1
    • collateral superficial veins (non-varicose)- score 1
    • alternative diagnosis as likely or greater than that of DVT- score -2
    . (2) bilateral impedance plethysmography- minimum of five inflation-deflation sequences. A graph was used comparing venous capitance and venous outflow. Impedance plethysmography was considered abnormal if highest rise and fall was on or below a set discrimination line.
    • In patients with symptoms in both legs, the most symptomatic leg is used.
    • Risk grouping according to clinical score
      • score 0 or less- low risk
      • score 1 or 2- moderate risk
      • score 3 or more- high risk
    • Suggested approach: clinical risk grouping followed by IPG then;
      • high risk: IPG positive- DVT: IPG negative- venogram, positive- DVT; negative- no DVT
      • moderate risk: IPG positive- USS or venogram positive- DVT; negative- no DVT; IPG negative- repeat IPG in one week; if positive- DVT; if negative- no DVT
      • low risk: IPG positive- venogram, if positive- DVT; negative-no DVT: IPG negative- no DVT

    The evidence

    pre-test probability of DVT: 30%, (95% CI: 26% to 34%)

    diagnostic test DVT no DVT LR
    (95% CI)    		 post-test probability
    score -2 0.02
    (0.001 to 0.32)     		%
    score 1 0.12
    (0.04 to 0.34)     		%
    score 0 0.37
    (0.22 to 0.61)     		%
    score 1 0.66
    (0.41 to 1.1)     		%
    score 2 2.7
    (1.6 to 4.5)     		%
    score 3 3.3
    (1.9 to 5.7)     		%
    score 4 18
    (6.9 to 49)     		%
    score 5 15
    (3.8 to 55)     		%
    score 6 or more 26
    (4.9 to 140)     		%
    total


    diagnostic test DVT no DVT LR+
    (95% CI)    		 post-test probability LR-
    (95% CI)    		 post-test probability
    impedance plethysmography 76 24 11
    (7.6 to 17)     		76% 0.25
    (0.17 to 0.36)     		7%
    total 99 354


    diagnostic test DVT no DVT LR+
    (95% CI)    		 post-test probability LR-
    (95% CI)    		 post-test probability
    IPG in high risk patients 48 4 2.6
    (1.2 to 6.0)     		92% 0.27
    (0.14 to 0.51)     		55%
    total 59 13


    diagnostic test DVT no DVT LR
    (95% CI)    		 post-test probability
    IPG in moderate risk patients 22 8 5.6
    (2.7 to 11)     		73%
    total 42 85


    diagnostic test DVT no DVT LR+
    (95% CI)    		 post-test probability LR-
    (95% CI)    		 post-test probability
    IPG in low risk patients 6 11 8.6
    (3.7 to 20)     		35% 0.63
    (0.42 to 0.95)     		4%
    total 15 236

    • Clinical prediction rule high (19% of patients)- DVT prevalence 85% (95% CI: 77%-92%).
    • Clinical prediction rule moderate (32% of patients)- DVT prevalence 33% (95% CI: 25% to 41%).
    • Clinical prediciton rule low (66% of patients)- DVT prevalence 5.3% (95% CI: 2.8% to 7.9%).
    • Physician's guess high (21% of patients)- DVT prevalence 73% (95% CI: 64% to 82%).
    • Physician's guess moderate (38% of patients)- DVT prevalence 29% (95% CI: 22% to 35%).
    • Physician's guess low (57% of patients)- DVT prevalence 5.3% (95% CI: 2.4% to 7.7%).

    Comments

    1. Clinical prediciton rule derived from Wells PS, Hirsch J, Anderson DR et al. Accuracy of clinical assessment of deep-vein thrombosis. Lancet 1995; 345: 1326-1330. Stepwise logistic regression analysis was performed on data to identify significant features. Coefficient rounded off to give score.
    2. Compare also with studies using clinical scoring and d-dimer testing. (e.g. Lennox AF, Delis KT, Serunkuma S, Zarka ZA, Daskalopoulou SE, Nicolaides AN. Combination of a clinical risk score and rapid whole blood d-dimer testing in the diagnosis of deep vein thrombosis in symptomatic patients. J Vasc Surg. 30:794-804)

    Citation

    1. Wells PS, Hirsch J, Anderson DR, et al: A simple clinical model for the diagnosis of deep-vein thrombosis combined with impedance plethysmography: potential for an improvement in the diagnotic process. Journal of Internal Medicine 1998; 243: 15-23
    Search Terms: hand search
    Contributor: Chris Ball and Clare Wotton, May 2000
    Reviewer: Thomas McGinn

    Clinical Question.
    Patient suspected deep venous thrombosis
    Intervention or Exposure clinical prediction rule, IPG
    Outcome diagnosis