A study of agreement between the Naranjo algorithm and WHO-UMC criteria for causality assessment of adverse drug reactions

Objectives: Reliability and usefulness of various adverse drug reaction (ADR) causality assessment scales have not been fully explored. There is no universally accepted method for causality grading of ADRs. In the present study we assessed agreement between the two widely used causality assessment scales, that is, the World Health Organization-Uppsala Monitoring Center (WHO-UMC) criteria and the Naranjo algorithm. Materials and Methods: The same observer assessed all ADRs (n = 913) collected between January 2010 and December 2012 using the WHO-UMC criteria and Naranjo algorithm at a tertiary care hospital in India. We found that the most frequently assigned causality category was "possible" with both the scales. Results: A disagreement in the causality assessment was found in 45 (4.9%) cases reflecting ′′poor′′ agreement between the two scales (Kappa statistic with 95% confidence interval = 0.143 [0.018, 0.268]). The mean time taken to assess causality of the ADR using the WHO-UMC criteria was shorter than that by the Naranjo algorithm. Conclusion: This study showed that there is a poor agreement between the WHO-UMC criteria and Naranjo algorithm with the former being less time-consuming.