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

Abstract

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.

Impact of reduction mammoplasty on the quality of life of obese patients suffering from symptomatic macromastia: A descriptive cohort study

“…A descriptive cohort study 13,14 was performed on 37 consecutive obese patients with a BMI ! 30 kg/m 2 , who underwent bilateral RM (exposure variable) for symptomatic breast hypertrophy by one surgeon at Valdecilla University Hospital (Santander, Spain) from March 2010 to March 2013.…”

Essentials of research methods in neurosurgery and allied sciences for research, appraisal and application of scientific information to patient care (Part I)

“…Due to limitations inherent in their design, they are primarily useful for the formulation of hypotheses that can be tested subsequently by analytic designs. Descriptive studies include: case reports, case series, and ecological studies,30 Additionally are descriptive cohorts and uncontrolled experimental (intervention) studies6 rarely mentioned in neurosurgical literature.…”

“…Although case reports are sometimes often confused with case series, Esene et al6,7 proved that 5 should be the maximum number of subjects in case reports and cases presented individually (without statistical pooling of data), whereas studies with more than 5 subjects should be reported as case series provided sampling is from outcome to exposure. This distinction is important when conducting meta-analysis as a meta-analysis of case reports ought to produce much more detailed information than that of case series 6. Case series are however, limited in discerning cause-effect relationship, or comparison of intervention 2.…”

“…Such are typical in neurosurgical practice and are termed “descriptive cohort studies” 6. The investigator “observes” patients allocated to an exposure (Dr. JJ’s technique) then follows-up to assess the outcome (tumor recurrence).…”

“…Additionally, over the last decade, a number of papers have been published on the mislabeling, misclassification and misuse of research methods in neurosurgery 5-11. Esene et al12 demonstrated the confusion as regards sample size in the reporting of case reports and case series, and further reported a 70% mislabeling of case series 6. In the same vein, other authors have reported a 52% misclassification of case control studies,13 problems of methodology and reporting of clinical trials10,11,14 with 48% of trials in neurosurgical literature being of “bad-to-moderate” quality 11.…”