Causality assessment of adverse drug reactions: comparison of the results obtained from published decisional algorithms and from the evaluations of an expert panel

PURPOSE: To compare the results of causality assessments of reported adverse drug reactions (ADR's) obtained from decisional algorithms with those obtained from an expert panel using the WHO global introspection method (GI) and to further evaluate the influence of confounding variables on algorithms ability in assessing causality. METHOD: Two hundred sequentially reported ADR's were included in this study. An independent researcher used algorithms, while an expert panel assessed the same reports using the GI, both aimed at evaluating causality. Reports were divided into three groups according to the presence, absence or lack of information on confounding variables. RESULTS: For the total sample, observed agreements between decisional algorithms compared with GI varied from 21% to 56%, average of 47%. When confounding variables were taken into account, agreements varied between 41% and 69%, average of 58%; 8% and 65%, average of 46% and 15% and 53%, average of 42% accordingly to the absence, lack of information or presence of confounding variables, respectively. The extend of reproducibility beyond chance was low for the total sample (average Kappa = 0.26) and within the groups considered. CONCLUSION: The overall observed agreement between algorithm and GI was moderate although poorly different from chance, confounding variables being a shortcoming of algorithms ability in assessing causality.