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Since spontaneous reporting of adverse drug reactions depends on the physician's opinion of the relationship between the drug and the adverse event, we compared physicians' opinions with the scores obtained by the causality assessment method used in France. During a 2 month period, all physicians who reported adverse drug reactions (ADRs) to our pharmacovigilance centre expressed their opinions on the causal link by means of visual analogue scales. ADR reports were then assessed with the French causality assessment method by a clinical pharmacologist who was blind to physicians' opinions. The assessment by both physicians and the standardized method was performed for 75 ADR cases involving 120 drugs. Physicians used a wide range of assessments, with a preponderance of extreme scores, resulting in a U-shaped distribution, while the standardized method gave generally low scores. Scores given by physicians were very high (causality considered very likely or likely) in 60% of cases and very low (causality considered unlikely or dubious/possible) in 32% of cases. Scores obtained using the causality assessment method were low (causality dubious/possible) in 89% of cases and causality considered likely in only 11 cases, essentially in cases with positive rechallenge. Complete agreement occurred in only 6% of cases. Adding complete agreement and minor discrepancies raised the percentage to 49%.

The information and case quality of 500 spontaneous and 500 published adverse drug reaction (ADR) reports were compared, including a study of the most common criteria used in different causality assessment methods. The criteria were more often of positive value in the published reports. Nevertheless, spontaneous reports play an important role in the detection of new ADRs.

Several standardized assessment procedures are currently used in the evaluation of adverse drug reactions (ADRs). Disagreement in rating ADRs can result from between-raters variability and between-methods differences in weighting the evidence. We eliminated between-raters variability by computer simulation of 1134 ADRs (including all the possible combinations of criteria currently used) and by automatic rating using different algorithms adapted from six published methods. Percentage agreement (Po) and weighted kappa test (Kw) between pairs of methods are always better than with randomized scores, but the strength of agreement is only moderate (0.26 < Po < 0.59; 0.14 < Kw < 0.51). The weightings of criteria are evaluated in terms of sensitivity, specificity, and predictive values. Criteria are neither sensitive (0.41 < Se < 0.70) nor specific (0.18 < Sp < 0.63) and have poor predictive values. Disagreements on weightings are considerable for three major criteria: timing of event, dechallenge, and alternative etiologic candidates. We discuss some ways of improving reliability of ADR diagnosis. Clinical Pharmacology and Therapeutics (1986) 40, 451–461; doi:10.1038/clpt.1986.206