Signal Detection
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. In the context of drug safety, the term is used in a similar sense.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. The results of this surveillance exercise intend to arouse suspicions and should always be followed up by in-depth investigations.
Signal Detection at the DSRU
At the DSRU, monitoring for unexpected findings is a key research activity. Two methods are applied: qualitative (medical evaluation) and quantitative (‘automated’ or ‘data mining’) techniques.
Qualitative methods are based on clinical evaluation which involves reviewing the data reported for a single case or series of cases. All the information reported by the GP is reviewed by a research fellow at the DSRU. When an event is highlighted as a possible drug safety signal, all similar cases are reviewed to decide if a further in-depth evaluation is required.
Quantitative methods complement the medical review by making use of computational power to analyse the large volume of data. These statistical techniques utilise calculations based on the number of cases reported and the time the person is taking a specific drug.
Incidence rates and risk ratios for reported events are calculated using data collected through PEM. By ranking the values obtained, events with higher frequencies are identified and are compared with the expected frequencies, for example, from the prescribing information.
Additionally, the accumulation of data over the past 25 years of post-marketing drug safety surveillance activity has built a rich database which allows the DSRU to develop signal detection methods that explore comparative analyses between drugs and therapeutic classes. These techniques include proportional risk ratios and incidence rate ratios.
Signal Detection Meeting
In addition to the in-house research, the DSRU has played a leading international role on the development of signal detection methodologies by organising, since 2000, the Biennial Conference on Signal Detection and Interpretation.