WHO-UMC Causality Assessment
Work through the WHO-UMC criteria. The tool suggests the highest category whose criteria are all met. The category you report remains your clinical judgement.
The categories
| Category | Criteria (all must apply) |
|---|---|
| Certain | Plausible time relationship; cannot be explained by disease or other drugs; plausible response to withdrawal; event definitive pharmacologically or phenomenologically, using a satisfactory rechallenge if necessary. |
| Probable / Likely | Reasonable time relationship; unlikely to be due to disease or other drugs; clinically reasonable response to withdrawal; rechallenge not required. |
| Possible | Reasonable time relationship; could also be explained by disease or other drugs; information on withdrawal may be lacking or unclear. |
| Unlikely | Time to onset makes a relationship improbable (but not impossible); disease or other drugs provide plausible explanations. |
| Conditional / Unclassified | More data are needed for proper assessment, or additional data are being examined. |
| Unassessable / Unclassifiable | Cannot be judged because information is insufficient or contradictory, and cannot be supplemented or verified. |