2013-06-04-世界卫生组织-The_use_of_the_WHO-UMC_system_for_standardised_case_causality_assessment_3页_148kb

WHO-UMC Causality Assessment System Summary

Causality assessment is essential in pharmacovigilance due to the inherent challenges of determining drug-related adverse reactions, where most cases are suspected but not definitively proven. The primary goal is to classify the relationship likelihood between a drug and an event, reducing ambiguity in case reports. Standardized systems, like the WHO-UMC approach, help classify relationships into categories such as Certain, Probable/Likely, Possible, Unlikely, Conditional/Unclassified, and Unassessable, based on factors like time relationship and alternative explanations.

Key Elements of the WHO-UMC System

• Purpose: Developed as a practical tool for standardized assessment, considering clinical-pharmacological aspects and documentation quality, focusing on unknown/unexpected adverse reactions.
• Strengths: Helps decrease assessor disagreement, classify relationship likelihood, classify individual case reports, improve evaluation, and change uncertainty where possible.
• Limitations: Cannot provide accurate quantitative measurement, distinguish valid from invalid cases, prove connections, or always eliminate uncertainty.
• Classification Categories:
  • Certain: Requires a plausible time relationship, no explanation by disease or other drugs, response to withdrawal, and definitive pharmacological or phenomenological event. Rechallenge if necessary and convincing.
  • Probable/Likely: Time relationship reasonable, unlikely attributable to other causes, no rechallenge required.
  • Possible: Time relationship reasonable, but alternative explanations possible or withdrawal information unclear.
  • Unlikely: Time relationship improbable, or another explanation more likely.
  • Conditional/Unclassified: More data needed for accurate assessment.
  • Unassessable: Insufficient or contradictory information.
• Application: Assessed by evaluating criteria fit with the case report. Start from higher categories and move down if evidence is weak, or vice versa. Useful for drug-drug interactions by evaluating the influencing drug in the patient's context.

This system aids in structured evaluation but relies on subjective judgment due to semantic variations in definitions. For ongoing practice, real-life case illustrations are provided, referencing key sources like Edwards et al. (1994), Meyboom et al. (1992, 1997).