[Meta-analysis of antiaggregant therapy trials. Proposal of an additional reading key]

The efficacy of drug treatment is conventionally assessed by clinical trials. In these studies, experimental design, data analysis and interpretation of results are based on statistical methods. It is difficult to relate to a specific patient the data obtained from statistically analysed studies of population. In our opinion the statistical parameter NNT (Number of patients Needed to Treat) indicates the effectiveness of a treatment taking into consideration the basal risk as well as the risk reduction after therapy. We applied the NNT parameter to data taken from the metaanalysis Antiplatelet Trialists' Collaboration concerning secondary prevention of adverse vascular events with antiplatelet drugs. We focused on the long-term effect of antiplatelet therapy on the adverse events reduction; in the first year of treatment we observed a NNT value of 37, in the second year a NNT value of 59 and in the third year a NNT value of 200; in the fourth year we found absence of effect. The NNT parameter allows us to evaluate immediately the economic consequences of therapeutic strategies and the clinical impact of a long-term treatment.