Unrelated | An adverse event (AE) that is not related to drug use |
Unlikely | An AE for which an alternative explanation is more likely (e.g., concomitant drugs and diseases), or the relationship in time suggests that a causal relationship is unlikely |
Possible | An AE that might be caused by drug use. An alternative explanation (e.g., concomitant drugs and diseases) is inconclusive. The relationship in time is reasonable; therefore, the causal relationship cannot be excluded |
Probable or likely | An AE that might be due to drug use. The relationship in time is suggestive (e.g., confirmed by a dechallenge). An alternative explanation is less likely (e.g., concomitant drugs or diseases) |
Certain | An AE that is listed as a possible ADR and cannot be reasonably explained by an alternative explanation (e.g., concomitant drugs and diseases). The relationship in time is highly suggestive; it is confirmed by a dechallenge and rechallenge |