Clinical "case series": a concept analysis

Abstract

Objectives: To analyze the concept of "case series" in the medical literature compared with case reports.

Methods: A PubMed search for articles published during 2009 which had "case series" in their title was performed. A total number of 621 articles were retrieved. 586 papers were included in the analysis and 35 were excluded (18 were commentary letters, 5 were not in English, and twelve could not be retrieved by our Library). The number of patients and category of these articles were analyzed.

Results: The median (range) of the number of cases of articles having "case series" in their title was 7 (1-6432) cases. 186/ 586 articles had less than 5 cases (31.7%, 95% CI (28.3-35.1%)). The median (range) of the number of cases of articles having "case report" as their publication type was 4 (1-178) cases. Out of the 219 articles categorized as case reports 114 (52.1%, 95% CI (45.6-58.6%)) had less than five cases.

Conclusions: The concept of "case series" is not well defined in the literature and does not reflect a specific research design. We suggest that a case series should have more than four patients while four paitents or less should be reported individually as case reports.

Keywords: Case report; case series; concept analysis; research design.

Figures

Figure 1

Number of subjects studied in papers published during 2009 by the U.S. National Library of Medicine, National Institutes of Health “ PubMed” that have “case series” in their title. Total number of publications = 586 papers

Figure 2

Number of subjects of papers published during 2009 by the U.S. National Library of Medicine, National Institutes of Health “PubMed” that have “case series” in their title and categorized as “case report”. Total number of publications = 219 papers