Determinants of signal selection in a spontaneous reporting system for adverse drug reactions

Aims Detection of new adverse drug reactions (ADR) after marketing is often based on a Manual review of reports sent to a Spontaneous Reporting System (SRS). Among the many potential signals that are identified, only a limite d number are important enough to require further attention. The goal of thi s study is to gain insight into factors contributing to the selection and d issemination of possible signals originating from the SRS maintained by the Netherlands Pharmacovigilance Foundation. Methods In a case control design, all signals (n=42) disseminated to the Me dicines Evaluation Board front the second quarter of 1997 until the third q uarter of 2000, which could be expressed as a combination of a single ATC c ode and a single WHO preferred term, were included. For each case, four con trols were matched in time. Logistic regression analysis was used to invest igate the influence of various factors, such as the fact whether the ADR or drug is new, the strength of the association, the seriousness of the react ion and the documentation of the reports. Results Multivariate analysis showed that the presence of a 'serious report ' (Odds Ratio 3.8, 95% CI 1.3, 11.0), a WHO 'critical term' (OR 4.7, 95% CI 1.8, 13), the ADR being Unlabelled (OR 6.1, 95% CI 2.3, 16) and the presen ce of a disproportionate association (OR 3.5, 95% CI 1.4, 8) were all indep endently associated with signal selection. The number of reports, and the t ime after marketing of the drug had no influence. Conclusions This study showed that selection of signals is based on both qu alitative and quantitative aspects. Knowledge of these factors may improve the efficiency of the underlying signal selection process.