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Case reports of suspected adverse drug reactions—systematic literature survey of follow-up

BMJ 2006; 332 doi: (Published 09 February 2006) Cite this as: BMJ 2006;332:335
  1. Yoon Kong Loke, senior lecturer in clinical pharmacology (y.loke{at},
  2. Deirdre Price, research assistant2,
  3. Sheena Derry, research assistant2,
  4. Jeffrey K Aronson, reader in clinical pharmacology2
  1. 1 School of Medicine, Health Policy, and Practice, University of East Anglia, Norwich NR4 7TJ
  2. 2 Department of Clinical Pharmacology, University of Oxford, Radcliffe Infirmary, Oxford OX2 6HE
  1. Correspondence to: Y Loke
  • Accepted 4 October 2005


Objective To determine whether anecdotal reports of suspected adverse drug reactions are valuable early warning signals.

Design Systematic literature survey

Data sources We evaluated all case reports of adverse drug reactions published in 1997 in five medical journals. Reports were excluded if the adverse reaction had previously been described in earlier publications and was already listed in the product information of the drug reference source (the British National Formulary (BNF) or the Medicines Compendium). We used the Web of Knowledge Citation Index and Medline for 2003 to identify follow-up studies.

Main outcome measures Primary: the number of suspected adverse reactions subjected to formal validation studies and the findings of these studies. Secondary: the number of instances in which the warning from the case report was incorporated into the product information.

Results We evaluated 63 suspected adverse reactions and found that most (52/63, 83%) had not yet been subjected to further detailed evaluation. Data from controlled studies that supported the postulated link between the drug and the adverse event were available in only three cases. Of the 48 agents listed in the drug reference sources, details of the suspected reaction were subsequently added to the Medicines Compendium in 15 instances, and to the BNF in seven instances. In each case, only one reaction had been confirmed.

Conclusions Published case reports of suspected adverse reactions are of limited value as suspicions are seldom subjected to confirmatory investigation. Furthermore, these alerts are not incorporated into drug reference sources in a systematic manner.


  • Embedded ImageReferences to the 63 included case reports (w1-w63) and nine validation studies (w64-w72) are

  • Contributors YKL developed the original idea and the protocol, abstracted and analysed data, wrote the manuscript, and is guarantor. DP and SD contributed to the development of the protocol, abstracted data, and prepared the manuscript. JKA developed the protocol and helped with the manuscript.

  • Funding SD was supported by a grant from the Sir Jules Thorne Trust.

  • Competing interests None declared.

  • Ethical approval Not required.

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