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The evaluation of the safety profile of any drug in humans centres around the randomized, controlled, clinical trial; however such studies consider a relatively small sample size of patients who are observed for a short period of time. Moreover, the strict inclusion criteria, and the exclusion of special groups such as the elderly, children and pregnant women, represent additional limitations of these trials with respect to drug safety.
Once the drug is marketed, spontaneous reporting systems, along with post-approval safety studies, are put in place to obtain further data on its safety profile. Spontaneous reporting is theoretically valuable for identifying events with low frequency and 'signals' about potential safety issues that can be verified through specific surveys. Even if spontaneous reporting is sensitive, cheap and considers all marketed drugs, there might be problems and limitations because under-reporting and other biases, in many cases, are not manageable.
One of the limitations of spontaneous reporting is that doctors may fail to identify and report illnesses that they do not suspect to be induced by a drug. This realization led to the development of systems based upon 'event' reporting in which the doctor did not need to diagnose or suspect the true cause, but was merely asked to record events. An event was defined as "a particular untoward happening experienced by a patient, undesirable either generally or in the context of his disease."[1]
W.H.W. Inman, one of the fathers of modern pharmacoepidemiology, identified the following seven major reasons ('the seven deadly sins') affecting a spontaneous reporting system:[2]
* Ignorance - only severe adverse drug reactions (ADRs) need to be reported.
* Diffidence - fear of appearing ridiculous for reporting merely suspected ADRs.
* Lethargy - procrastination, lack of interest or time to find a report card, and indifference; the one case that an individual doctor might see could not contribute to medical knowledge.
* Ambition - to publish a personal case or a case series.
* Complacency - only safe drugs are allowed on the market.
* Guilt - for having caused an adverse effect.
* Fear - of possible litigation.
To overcome them, Professor Inman developed the Yellow Card scheme and Prescription Event Monitoring (PEM) in the UK. However, these reporting systems are not applicable in...