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J Clin Epidemiol. 2005 Dec;58(12):1227-32. Epub 2005 Sep 12.

Case reports and case series from Lancet had significant impact on medical literature.

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Department of Dermatology, University of Pennsylvania, Philadelphia, 19104, USA.



Case reports and case series are often the first evidence of innovative treatment, but clinical trials need to follow to substantiate this evidence. The objective of this article was to evaluate case reports or case series describing innovative treatment concerning their impact.


Case reports and case series (n < or = 10) from a high-impact journal, The Lancet, published from 1 January 1996 to 30 June 1997, were evaluated according to predefined criteria. To assess publication impact, Pubmed, Science Citation Index, the Register of Current Controlled Clinical Trials, and the Cochrance Controlled Clinical Trials Register were searched.


Sixty-four case reports and 39 case series were identified. They were cited in average 17 times (median 6,5; range 0-336). Twenty-Four follow-up trials were identified, nine in the register of current controlled clinical trials.


Case reports and case series can be well received, and have significant influence on subsequent literature and possibly on clinical practice. Many were followed by clinical trials. Often, though, they report rare conditions for which trials may not be feasible, and more or less explicitly transfer established treatment into other conditions. Overall, there is a strong publication bias favoring positive results, and opportunity should be created for publication of follow-up reports.

[Indexed for MEDLINE]

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