There is always a place in adverse reaction monitoring for the isolated case report, no matter how poorly documented it is or how unlikely the drug-event association appears to be; to question this principle is to undermine an important means of early detection of adverse effects. The corollary is naturally that all available reports must as time passes be reviewed again and those that have remained isolated instances be discarded as coincidental unless there is a sound reason for believing in their validity. It is also important to avoid the snowballing effect which can easily lead one onto a false trail.
