Case-control studies in neurosurgery

Abstract

Object Observational studies, such as cohort and case-control studies, are valuable instruments in evidence-based medicine. Case-control studies, in particular, are becoming increasingly popular in the neurosurgical literature due to their low cost and relative ease of execution; however, no one has yet systematically assessed these types of studies for quality in methodology and reporting. Methods The authors performed a literature search using PubMed/MEDLINE to identify all studies that explicitly identified themselves as “case-control” and were published in the JNS Publishing Group journals (Journal of Neurosurgery, Journal of Neurosurgery: Pediatrics, Journal of Neurosurgery: Spine, and Neurosurgical Focus) or Neurosurgery. Each paper was evaluated for 22 descriptive variables and then categorized as having either met or missed the basic definition of a case-control study. All studies that evaluated risk factors for a well-defined outcome were considered true case-control studies. The authors sought to identify key features or phrases that were or were not predictive of a true case-control study. Those papers that satisfied the definition were further evaluated using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist. Results The search detected 67 papers that met the inclusion criteria, of which 32 (48%) represented true case-control studies. The frequency of true case-control studies has not changed with time. Use of odds ratios (ORs) and logistic regression (LR) analysis were strong positive predictors of true case-control studies (for odds ratios, OR 15.33 and 95% CI 4.52–51.97; for logistic regression analysis, OR 8.77 and 95% CI 2.69–28.56). Conversely, negative predictors included focus on a procedure/intervention (OR 0.35, 95% CI 0.13–0.998) and use of the word “outcome” in the Results section (OR 0.23, 95% CI 0.082–0.65). After exclusion of nested case-control studies, the negative correlation between focus on a procedure/intervention and true case-control studies was strengthened (OR 0.053, 95% CI 0.0064–0.44). There was a trend toward a negative association between the use of survival analysis or Kaplan-Meier curves and true case-control studies (OR 0.13, 95% CI 0.015–1.12). True case-control studies were no more likely than their counterparts to use a potential study design “expert” (OR 1.50, 95% CI 0.57–3.95). The overall average STROBE score was 72% (range 50–86%). Examples of reporting deficiencies were reporting of bias (28%), missing data (55%), and funding (44%). Conclusions The results of this analysis show that the majority of studies in the neurosurgical literature that identify themselves as “case-control” studies are, in fact, labeled incorrectly. Positive and negative predictors were identified. The authors provide several recommendations that may reverse the incorrect and inappropriate use of the term “case-control” and improve the quality of design and reporting of true case-control studies in neurosurgery.

COSMOS-E: Guidance on conducting systematic reviews and meta-analyses of observational studies of etiology

“…Indexing of observational study designs is often inadequate, and authors may themselves confuse designs. In specialty journals, 30%–50% of studies indexed as 'case-control studies' are not in fact case-control studies [38,39]. Characteristics of study participants and outcomes are extracted separately for exposed and unexposed (cohort studies) or cases and controls (case-control studies).…”

How Often Do Orthopaedic Matched Case-Control Studies Use Matched Methods? A Review of Methodological Quality

“…Case-control studies were defined according to Breslow and Day [4] as: "…an investigation into the extent to which persons selected because they have a specific disease (the cases) and comparable persons who do not have the disease (the controls) have been exposed to the disease's possible risk factors to evaluate the hypothesis that one or more of these is a cause of the disease." This definition is consistent with the classic epidemiologic understanding of case-control studies and similar evaluative studies in other specialties [4,11,12,18,19]. Only individually or frequency-matched studies were used, because other matching strategies (for example, propensity score-matching) require different statistical methods [1].…”

Grab Control! Choosing the Right Comparison Group in an Observational Study

“…In fact, one recent report assessing studies labeled as case-control in the Journal of Neurosurgery Publishing Group ( Journal of Neurosurgery , Journal of Neurosurgery: Pediatrics , Journal of Neurosurgery: Spine , and Neurosurgical Focus ) or Neurosurgery found only 48% of the studies were in fact case-control studies. 1 Many of the rest were retrospective cohort studies. Remember, a retrospective cohort study identifies groups based on their treatment while a case-control study identifies groups based on their outcome.…”