Geographical variation in adverse event reporting rates in clinical trials

A group of 13,698 patients from 127 gastro-intestinal clinical trials, conducted in 13 countries was included in the analyses. All adverse events reported were included in the evaluation. The general adverse event reporting rate, the mean number of adverse events reported, the serious adverse event reporting rate and the mean number of serious adverse events reported were calculated for each country. In addition, the pattern of adverse events reported in each country was studied. The general adverse event reporting rate varied between 17% and 68% with a mean of 47% and the serious adverse event reporting rate varied between 1% and 20% with a mean of 8%. The mean number of adverse events, reported by patients reporting adverse events, varied between 1.5 and 2.7 with a mean of 2.1 and the mean number of serious adverse events, reported by patients reporting serious adverse events, varied between 1.1 and 1.7 with a mean of 1.4. In addition to these differences, patients/investigators had a tendency to put emphasis on different kinds of adverse events in different countries.