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[Creative mathematics with clopidogrel; exaggeration of the preventive effect by manufacturer]
A Algra1, J van Gijn, L J Kappelle
1Academisch Ziekenhuis, Julius Centrum voor Patiëntgebonden Onderzoek, Utrecht.
Insights
A miscalculation overstated clopidogrel
Area of Science:
- Clinical Pharmacology
- Medical Statistics
- Cardiovascular Research
Background:
- Advertisements in Dutch medical journals promoted clopidogrel, claiming a 26% reduction in ischemic complications versus aspirin.
- This claim was based on a miscalculation by the manufacturer, Sanofi-Synthelabo.
- Accurate analysis reveals a significantly smaller benefit of clopidogrel compared to aspirin.
Purpose of the Study:
- To correct a miscalculation in the reported efficacy of clopidogrel treatment.
- To accurately determine the reduction in ischemic complications attributed to clopidogrel versus aspirin.
Main Methods:
- Re-evaluation of reported event rates for clopidogrel and aspirin treatments.
- Comparison of actual treatment outcomes against a hypothetical placebo group.
- Calculation of absolute and relative risk reductions for ischemic complications.
Main Results:
- The reported 26% reduction in ischemic complications is an overstatement.
- The actual absolute reduction in ischemic complications is 0.51%.
- The actual relative reduction in ischemic complications is 8.7%.
Conclusions:
- The manufacturer's calculation method led to a significant overestimation of clopidogrel's benefit.
- The true therapeutic advantage of clopidogrel over aspirin in reducing ischemic complications is considerably less than advertised.
- Accurate statistical reporting is crucial for evidence-based medical decision-making.
Abstract:
A number of Dutch medical journals recently carried an advertisement stating that clopidogrel treatment reduced the number of ischaemic complications with 26%, compared with aspirin treatment. This is a miscalculation: the actual reduction is 0.51% in absolute rates, and 8.7% in relative terms. The error by Sanofi-Synthelabo arose by comparison of the event rates for clopidogrel (5.32%) as well as for aspirin (5.83%) with that in an imaginary placebo group (7.77%), yielding a reduction of ischaemic complications of 2.45% and 1.94% respectively; erroneous comparison of these two numbers leads to a difference of 26%.