Agreement and correlation between WHO-UMC Causality scale and the Naranjo algorithm for causality assessment of adverse drug reactions at tertiary care center in Northern India.

Abstract

Background: To develop a structured and harmonized causality assessment method has been a holy grail in pharmacovigilance. The Pharmacovigilance Programme of India (PvPI) recommends the use of the World Health Organization-Uppsala Monitoring Centre (WHO-UMC) scale, whereas many clinicians prefer the Naranjo algorithm for its simplicity. There is no universally accepted method for the causality grading of ADRs. In the present study, we assessed agreement and correlation between the two widely used causality assessment scales, that is, the WHO-UMC criteria and the Naranjo algorithm.

Materials and methods: In this study, 313 individual case safety reports were analyzed from April 1, 2020, to March 31, 2023, reported at the Adverse Drug Reaction Monitoring Center (AMC) at Kalpana Chawla Government Medical College, Karnal. Two well-trained independent groups performed a causality assessment. One group performed a causality assessment of 313 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. Spearman's correlation was also used to find the correlation between the two scales.

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. A weak agreement was found between the two scales (Kappa statistics with 95% confidence interval = 0.463, [P < 0.001]). Spearman's correlation coefficient was found to be 0.506.

Conclusion: The assessment of causality for adverse drug reactions (ADRs) is challenging, and none of the different methods available for assessing ADR causality is accepted as the gold standard. In our study, we found weak agreement between the WHO-UMC criteria and the Naranjo algorithm. It is essential to standardize the causality assessment tool to create a universally acceptable method for assessing causality. Further research is needed to establish a gold standard method for assessing the causality of adverse drug reactions.