Comparison of different methods for causality assessment of adverse drug reactions

Background The causality assessment of adverse drug reactions (ADRs) remains a challenge, and none of the different available method of causality assessment used for assessing adverse reactions has been universally accepted as the gold standard. Objective To examine the agreement and correlation among three broad approaches for causality assessment of ADRs viz. World Health Organization-Uppsala Monitoring Centre (WHO-UMC) system, Naranjo algorithm, and updated Logistic method. Setting ADR monitoring centre (AMC) of a tertiary care teaching hospital in India. Method A total of 230 cases of ADR from April 2017 to August 2017 were retrospectively analyzed by each of these three methods. The agreement among the different methods was calculated by Cohen’s kappa (κ), and Spearman’s correlation was used to find the correlation among these methods. Main outcome measures Cohen’s kappa value and Spearman’s correlation coefficient for comparison among the different methods. Results The Cohen’s κ used for analyzing the agreement between WHO-UMC system and Naranjo algorithm was 0.45, between WHO-UMC system and updated Logistic method was 0.405, and between Naranjo algorithm and updated Logistic method was 0.606. The Spearman’s correlation coefficient was 0.793 for Naranjo algorithm vs. updated Logistic method, 0.735 for WHO-UMC system vs. Naranjo algorithm, and 0.696 for WHO-UMC system vs. updated Logistic method. Conclusion Causality assessment based on objective measurements (scores and probabilities) like updated Logistic method and Naranjo algorithm are less prone to subjective variations compared to the WHO-UMC system which is based on expert judgement.