[The authors respond:]
We are gratified by the attention paid to our discussion of adverse drug reactions in Canada. [1] Both the letter by David Rosenbloom and Christine Wynne and an earlier letter by Joel Lexchin [2] support our view that deaths associated with adverse drug reaction are probably underreported. We still believe, however, that the original estimate by Lazarou and colleagues [3] was flawed for methodological reasons related to their meta-analysis. Their estimate is likely compromised by publication bias, by biases in the original studies, by reporting bias and because the application of US data to Canada was inappropriate. We used an alternative method, namely analysis of routinely collected hospitalization data, to argue that the true estimate of mortality associated with adverse drug reactions was likely to be lower than that reported from the meta-analysis.
We believe that the discrepant estimates of mortality associated with adverse drug reactions highlight the importance of this issue. In Ontario, the prevalence of adverse drug reactions is increasing. [4] The inescapable conclusion is that a substantial number of Canadians suffer from adverse drug reactions, with a consequent risk of related mortality. The fundamental question remains: Who has the responsibility for monitoring these events? It is clear that current reporting methods are inadequate and that better methods are needed to accurately measure mortality associated with adverse drug reactions.
Duncan Hunter, PhD
Namrata Bains, MSc
Health Information Partnership; Eastern Ontario Region; Kingston, Ont.