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Case series and descriptive cohort studies in neurosurgery: the confusion and solution

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Abstract

Background

Case series (CS) are well-known designs in contemporary use in neurosurgery but are sometimes used in contexts that are incompatible with their true meaning as defined by epidemiologists. This inconsistent, inappropriate and incorrect use, and mislabeling impairs the appropriate indexing and sorting of evidence.

Method

Using PubMed, we systematically identified published articles that had “case series” in the “title” in 15 top-ranked neurosurgical journals from January 2008 to December 2012. The abstracts and/or full articles were scanned to identify those with descriptions of the principal method as being “case series” and then classified as “true case series” or “non-case series” by two independent investigators with 100 % inter-rater agreement.

Results

Sixty-four articles had the label “case series” in their “titles.” Based on the definition of “case series” and our appraisal of the articles using Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines, 18 articles (28.13 %) were true case series, while 46 (71.87 %) were mislabeled. Thirty-five articles (54.69 %) mistook retrospective (descriptive) cohorts for CS.

CS are descriptive with an outcome-based sampling, while “descriptive cohorts” have an exposure-based sampling of patients, followed over time to assess outcome(s). A comparison group is not a defining feature of a cohort study and distinguishes descriptive from analytic cohorts.

Conclusion

A distinction between a case report, case series, and descriptive cohorts is absolutely necessary to enable the appropriate indexing, sorting, and application of evidence. Researchers need better training in methods and terminology, and editors and reviewers should scrutinize more carefully manuscripts claiming to be “case series” studies.

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Abbreviations

STROBE:

Strengthening the Reporting of Observational Studies in Epidemiology

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Acknowledgments

The authors would like to express their special appreciation and thanks to Dr. Anna M. Sikod for the artistic drawings transforming thousands of complex words into simple speakable schemas. We would also like to thank all of our friends, colleagues, and teachers who supported us in writing and incented us to strive toward our goal. Worth mentioning are the staff members of the Department of Neurosurgery, Ain Shams University and Nasser Institute Gamma Knife Center, Cairo, Egypt. Lastly, our sincere appreciation to Professor Concezio Di Rocco, for giving this piece of work its due consideration and for supporting young researchers from developing countries.

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Authors and Affiliations

  1. Department of Neurosurgery, Ain Shams University, Cairo, Egypt

    Ignatius N Esene, Mohamed El Zoghby, Ali Kotb & Hossam El Husseiny

  2. Gamma Knife Center, Nasser Institute, Cairo, Egypt

    Ignatius N Esene

  3. Encyclopaedia Neurochirurgica, Paris, France

    Ignatius N Esene

  4. Department of Surgery, The University of Arizona College of Medicine, Tucson, AZ, USA

    Julius Ngu

  5. Department of Neurosurgery, School of Medicine, Koç University, Istanbul, Turkey

    Ihsan Solaroglu

  6. Family Medicine Morehouse, Atlanta, GA, 30344, USA

    Anna M. Sikod

  7. African Journal of Neurological Sciences (A.J.N.S), Ivory Coast, Africa

    Gilbert Dechambenoit

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  1. Ignatius N Esene
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Correspondence to Ignatius N Esene.

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Esene, I.N., Ngu, J., El Zoghby, M. et al. Case series and descriptive cohort studies in neurosurgery: the confusion and solution. Childs Nerv Syst 30, 1321–1332 (2014). https://doi.org/10.1007/s00381-014-2460-1

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