Venous thromboembolism: prophylaxis: aspirin reduces symptomatic venous thromboembolism without reducing mortality

Clinical bottom line (level 1b)

  1. Patients undergoing hip or knee surgery who take aspirin compared with placebo for 35 days are less likely to develop symptomatic venous thromboembolism (NNT = 150 at 35 days) .
  2. There is no effect on mortality.
  3. There is no clear effect on fatal haemorrhage or bleeding requiring transfusion.
Pulmonary Embolism Prevention (PEP) Trial Colloborative Group : Lancet 2000; 355 : 1295-1302
Expires April 2003

The study

Double-blinded ?concealed randomised trial with intention-to-treat
Setting: 148 acute hospitals, Australia, New Zealand, South Africa, Sweden and UK

17444 patients (aged mean 79, 79% female) having surgery for hip fracture (77%) or elective hip or knee arthroplasty

Excluded if
  • clear indication for aspirin (e.g. myocardial infarction)
  • clear contraindication to aspirin (e.g. active peptic ulcer)

    Control Group: (n = 8675, 8675 analysed): placebo
    Experimental Group: (n = 8726, 8726 analysed): aspirin 160 mg daily for 35 days

    99% followed for 35 days
    Outcome notes:
    • pulmonary embolism or symptomatic DVT : PE diagnosed if positive pulmonary angiogram, high probability ventilation-perfusion scan, an intermediate probability scan with venogrpahic evidence of a DVT, or evidence of PE on autopsy; DVT diagnosed if confirmed on venogram or other objective method

    The evidence

    Outcome Time to outcome CER EER RRR
    (95% CI)    		 ARR
    (95% CI)    		 NNT
    (95% CI)
    pulmonary embolism or symptomatic DVT 35 days 201
    (2.32%)    		 143
    (1.64%)    		 29%
    (13% to 43%)    		 0.68%
    (0.26% to 1.09%)    		 150
    (92 to 380)
    death 35 days 472
    (5.44%)    		 456
    (5.23%)    		 4%
    (-9% to 15%)    		 0.22%
    (-0.45% to 0.88%)    		 470
    (NNT = 110 to infinity;
    NNH = 220 to infinity)
    bleed requiring transfusion 35 days 360
    (4.15%)    		 410
    (4.70%)    		 -13%
    (-30% to 1%)    		 -0.55%
    (-1.16% to 0.062%)    		 -180
    (NNT = 1600 to infinity;
    NNH = 86 to infinity)
    fatal haemorrhage 35 days 15
    (0.17%)    		 13
    (0.15%)    		 14%
    (-81% to 59%)    		 0.024%
    (-0.10% to 0.14%)    		 4200
    (NNT = 700 to infinity;
    NNH = 1100 to infinity)

    Comments

    1. Patients were not excluded if they were taking other thromboprophylactic measures or had previously used aspirin or other NSAIDs.

    Citation

    1. Pulmonary Embolism Prevention (PEP) Trial Colloborative Group , : prevention of pulmonary embolism and deep vein thrombosis with low dose aspirin: pulmonary embolism prevention (PEP) trial. Lancet 2000; 355 : 1295-1302
    Search Terms: hand-search
    Contributor: Chris Ball, April 2000
    Reviewer:

    Clinical Question.
    Patient hip surgery or knee surgery
    Intervention or Exposure aspirin
    Comparison placebo
    Outcome venous thromboembolism, death, bleeding