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Table 1 Characteristics of published instruments assessing causal relationship between medication exposure and adverse events

From: Use of case reports and the Adverse Event Reporting System in systematic reviews: overcoming barriers to assess the link between Crohn’s disease medications and hepatosplenic T-cell lymphoma

  Naranjo Kramer WHO
Numerical range −4 to +13 −7 to +7 n/a
Format Ten questions answered ‘yes,’ ‘no,’ or ‘don’t know,’ each with a numerical value; numbers summed for final score. Higher scores indicate greater likelihood of causality. An algorithm with six separate axes/flowcharts. Each axis contributes points to the final score. Higher scores indicate greater likelihood of causality. Contains six categories; the user selects the one for which most criteria are met.
Distinguishes irreversible adverse events from other adverse events? No Yes No
Addresses methods used to confirm adverse event? Yes No No
Asks about serum medication levels? Yes Yes No
Considers prior experience with medication? Yes Yes Yes
Considers alternate etiologies? Yes Yes Yes
Questions about rechallenge? Yes Yes Yes
Questions about dechallenge? Yes Yes Yes
  1. n/a, not applicable; WHO, World Health Organization.