Revised: 3 July 2013

Committees

Adverse Reaction Reporting - Definition of Causality

Certain:

• the event occurred with a plausible time relationship to medicine use;
• it could not be explained by concurrent diseases, or other medicines or substances;
• withdrawal of the medicine resulted in recovery or significant improvement, and reinitiation ("rechallenge") of the medicine, if it was appropriate, resulted in recurrence of the same event; and
• the event was a recognisable pharmacological action of the medicine or a clearly identifiable clinical event.

Probable:

the occurrence of the event was temporally associated with administration of the medicine, it was unlikely to be caused by a concurrent disease or other medicine or substance, and withdrawal of the medicine resulted in improvement or recovery.

Possible:

the occurrence of the event was temporally associated with administration of the medicine, but it could also be explained by concurrent disease or other medicine or substance, and/or details such as administration dates or response to withdrawal of the medicine may have been absent or unclear.

Unlikely:

the event occurred at a time in relation to medicine administration which made causation improbable. Concurrent disease or other medicine or substance may have provided a plausible explanation.

Unclassified:

more data were required in order to assess the adverse event.

Unclassifiable:

the data available were insufficient or contradictory, and it was not possible to obtain further data or verify existing data.