The plural of anecdote is not data...

Glenn McGee penned a fairly strong critique of the role of the case report in the continuum of clinical research in The Scientist, "The Plural of Anecdote is Not Ambien" (registration required).

The article uses the example of case reports describing the use of Ambien to induce changes in consciousness among several patients in a persistent vegetative state.

"A paradox of biomedical research is that huge controlled trials, meta-analyses, and reviews of the literature are ubiquitous, but the number of "case reports" - and journals comprised entirely of incidental "findings" - is growing. The media has no idea how to deal with case reports....Investigators who jumpstart their programs with case reports are often in search of research support, as was Claus - who as a result of the case report is now funded. In this respect they, and the journals who publish nothing but these case reports, are like the television producers I worked with: They aim at using the power of stories to make the claims and reap the rewards that come from research, but without doing the research."

It's clear that the media picks up dramatic stories like the Ambien cases mentioned above, but I would argue that the media also misrepresents or over-hypes the implications of stronger types of clinical research as well (clinical trials, cohorts, etc.). While case reports are certainly limited in terms of generalizability and firm conclusions, they serve a useful function in generating and testing initial hypotheses.

A few articles that continue the role of the case report in scientific exploration:
- Carey JC. Significance of case reports in the advancement of medical scientific knowledge. Am J Med Genet A. 2006 Oct 1;140(19):2131-4. PubMed citation
- Vandenbroucke JP. In defense of case reports and case series. Ann Intern Med. 2001 Feb 20;134(4):330-4. PubMed citation
- Kagan AR, Burchette RJ, Iganej S. The case for case reports: avoiding statistical seduction. Am J Clin Oncol. 2006 Aug;29(4):325-7. PubMed citation