Characteristics of Spontaneous Reports
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It is well known that reporting is biased: severe ADRs are more likely to be reported; known reactions are less likely to be reported.
CHARACTERISTICS OF SPONTANEOUS
REPORTS
It
is well known that reporting is biased: severe ADRs are more likely to be
reported; known reactions are less likely to be reported. In the United
Kingdom, there is a tendency for reporting rates to be higher when a drug is
newly introduced to the market, but the effect of media or regulatory action
may distort this pattern. The consequence is that reporting rates cannot be
relied upon as estimates of the incidence of adverse reactions. This situation
will always apply, and although there may be calls from those unfamiliar with
pharmacovigilance to improve reporting rates so that spontaneous reports do
reflect true incidence, this is not their purpose. They can be used to detect
signals, and they are certainly capable of doing this.
Given
the biases in reporting rates, one obvious way to assess the strength of a
signal is to study the spon-taneous reports alone without an external
comparison group. This means that many of the biases that apply to reporting
rates will apply to all reports, and within the database an increased validity
of comparison may be made.
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