BMJ  2003;327:750 (27 September), doi:10.1136/bmj.327.7417.750-a

Letter

Balancing benefits and harms in health care

Observational data on harm should complement systematic reviews of benefit

EDITOR—The meeting on "rare events" mentioned by Cuervo and Clarke was an opportunity to bridge two worlds: the world of systematic reviews of randomised trials, which investigate benefits of treatment, and the world of pharmacoepidemiology, which mainly investigates the harms of the same treatments.¹ Bridging will not be easy.

On one hand, there are entrenched views about the superiority of randomised evidence, leading to prejudices that there has been no reliable progress except for randomised trials, that case reports are biased (despite evidence to the contrary about adverse effects²), or that observational databases are intrinsically problematic. This attitude ignores established differences between discovery and verification, and between investigating intended and non-intended effects of treatments.^{3 4}

On the other hand, discussions about epidemiological methods as applied to adverse drug reactions can become so arcane that only a few people still follow.⁵ Judging observational research on harm will entail more knowledge of subject matter and will be less easily codified than judgments about randomised trials.

However, participants from both fields wanted to think about incorporating the other in future activities, perhaps by giving young people dual training in both types of research. This should lead to a future where several types of evidence can be entered in a single systematic review to present a true balance of risks and benefits.

Leiden University Medical Centre, PO Box 9600, NL-2300 RC Leiden, Netherlands j.p.vandenbroucke{at}lumc.nl

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Competing interests: None declared.

References

1. Cuervo LG, Clarke M. Balancing benefits and harms in health care. BMJ 2003;327: 65-6. (12 July.)[Free Full Text]
2. Chalmers I. Geoffrey Venning's classic BMJ paper [electronic response to Aronson J. Anecdotes as evidence]. bmj.com 2003. bmj.com/cgi/eletters/326/7403/1346#33806 (accessed 4 September 2003).
3. Jick H. The discovery of drug-induced illness. N Engl J Med 1977;296: 481-5.[Abstract]
4. Miettinen OS. The need for randomization in the study of intended effects. Stat Med 1983;2: 267-71.[Medline]
5. Skegg DCG. Third generation oral contraceptives. BMJ 2000;321: 190-1.[Free Full Text]

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