Agreement between WHO-UMC causality scale and the Naranjo algorithm for causality assessment of adverse drug reactions

Background: The Pharmacovigilance Program of India recommends the use of the World Health Organization-Uppsala Monitoring Centre (WHO-UMC) scale, while many clinicians prefer the Naranjo algorithm for its simplicity. In the present study, we assessed agreement between the two widely used causality assessment scales, that is, the WHO-UMC criteria and the Naranjo algorithm. Materials and Methods: In this study, 842 individual case safety reports were randomly selected from 1000 spontaneously reported forms submitted to the ADR Monitoring Center at a tertiary healthcare Institute in Central India between 2016 and 2018. Two well-trained independent groups performed the causality assessment. One group performed a causality assessment of the 842 ADRs using the WHO-UMC criteria and the other group performed the same using the Naranjo algorithm. The agreement between two ADR causality scales was assessed using the weighted kappa (κ) test. Results: Cohen's kappa coefficient (κ) statistical test was applied between the two scales (WHO-UMC scale and Naranjo algorithm) to find out the agreement between these two scales. “No” agreement was found between the two scales {Kappa statistic with 95% confidence interval = 0.048 (P < 0.001)}. Conclusion: There was no agreement found between the WHO-UMC criteria and the Naranjo algorithm in our study