[Can the sub-notification of drug adverse effects by capture/recapture method be evaluated?]

The incidence of adverse effects of a drug can be evaluated from the relationship between adverse effects reported to the drug company and to French drug surveillance centres and the number of patients exposed to the drug. Many adverse effects are never reported and this under-reporting is variable. The capture/recapture method can be used in drug surveillance to evaluate the importance of under-reporting for an adverse effect of a drug. This method, based upon the intersection of two different data sources with the aim of identifying the number of common cases, can estimate the number of unreported cases if at least two independent data sources are available. Scrupulous identification of each case and of common cases and study of the independence of the two systems are essential for this method. The application of the capture/recapture method to spontaneous reporting permits the estimation of the total number of cases and the completeness of registration of the two data sources (the drug company and the French drug surveillance centres). This application of the capture/recapture method needs to be validated by comparing the results to the results of prospective studies whenever possible.