WHO-UMC Scale
The WHO-Uppsala Monitoring Centre (UMC) system for standardized case causality assessment.
- Certain: A plausible reaction that cannot be explained by other factors and follows a known response pattern to the suspected drug.
- Probable: A likely reaction with a reasonable time sequence, which is unlikely to be attributed to other factors.
- Possible: The reaction could be explained by the drug, but other factors could also be the cause.
- Unlikely: The reaction is not likely related to the drug; another cause is more plausible.
- Conditional/Unclassified: More data is required for a proper assessment.
- Unassessable/Unclassifiable: The report is incomplete or contradictory and cannot be judged.
Naranjo Score / Algorithm
A questionnaire-based method to assess the probability of an adverse drug reaction. The total score determines the category.
- Definite (≥9): High level of certainty that the event is an ADR.
- Probable (5-8): The event is likely an ADR.
- Possible (1-4): The event could be an ADR.
- Doubtful (0): The event is unlikely to be an ADR.