What is a signal?
A ‘signal’ consists of reported information on a possible causal relationship between an adverse event and a drug, the relationship being unknown or incompletely documented previously. Usually more than a single report is required to generate a signal, depending upon the seriousness of the event and the quality of the information.
What is signal detection?
Early identification of the hazards associated with drugs is the main goal of those involved in pharmacovigilance ‘Signal detection’, ‘signal generation’ or ‘signalling’ refers to a process that aims to find, as soon as possible, any indication of an unexpected drug safety problem which may be either new ADRs or a change of the frequency of ADRs that are already known to be associated with the drugs involved. The results of this surveillance exercise tend to arouse suspicions and should always be followed up by in-depth investigations. Spontaneous reporting systems for suspected adverse drug reactions (ADRs) remain a cornerstone of pharmacovigilance.
Signal detection at the DSRU
At the DSRU, monitoring for unexpected findings is a key research activity. Two methods are applied:
- Qualitative methods are based on clinical evaluation by a Research Fellow who reviews data reported by the GP for a single case or series of cases.
- Quantitative (‘automated’ or ‘data mining’) techniques complement the medical review by making use of computational power to analyse the large volume of data. These statistical techniques provide estimates of the extent of how the number of observed cases differs from the number of expected cases. The underlying principle is to explore indicators of disproportionality that may then reveal associations of interest. Different measures include ranking of incidence rates and risks within time periods, risk and/or rate ratios between time periods, and reasons for treatment withdrawal. The data may also compared with the expected frequencies (e.g. from prescribing information), or from external data sources.
Through our extensive experience in this area, we are able to offer advice and collaborate with partners on all aspects of signal detection and incorporating these techniques into risk management studies.
Signal Detection Conference
In addition to the in-house research, the DSRU has played a leading international role in the development of signal detection methodologies by organising the popular biennial conference on “Signal Detection and Interpretation in Pharmacovigilance” since 2001.