Definition

The phenomenon where only a fraction of actual adverse events are reported to spontaneous reporting systems, typically estimated at 1-10% of actual occurrences.

Example

A serious adverse reaction may actually occur in 1 in 1,000 patients, but only 1 in 10,000 gets reported to the spontaneous system due to underreporting.

Regulatory source

Pharmacoepidemiology Literature

Common mistakes

Treating spontaneous report counts as actual case counts, leading to gross underestimation of risk.

Inspector question

How do you account for underreporting in your safety analyses and signal evaluation?

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