Hospital visitors as controls in case-control studies

Area of Science:

• Epidemiology
• Public Health
• Oncology

Background:

• Selecting appropriate controls is a critical challenge in case-control study design.
• Hospital-based controls may introduce bias, and population-based controls are often difficult to access.
• The Instituto Nacional de Câncer (INCA) in Brazil conducted a study to address this control selection issue.

Purpose of the Study:

• To evaluate the utility of using hospital visitors as controls in a case-control study.
• The study focused on identifying risk factors for breast cancer, including organochlorine compounds.
• This research specifically examined the feasibility of using hospital visitors as controls at INCA.

Main Methods:

• 177 incident breast cancer cases and 377 female hospital visitors were recruited.
• Three control group models were compared: all visitors, visitors excluding those with relatives with breast cancer, and visitors excluding those with relatives with any cancer.
• Odds ratios (OR) and 95% confidence intervals were calculated to assess associations.

Main Results:

• Risk factor associations (excluding family history) were consistent across the three control models.
• Family history of breast cancer emerged as a significant risk factor in models excluding visitors with relatives with cancer.
• Multivariate analysis confirmed the significance of family history of breast cancer in specific control models.

Conclusions:

• Hospital visitors represent a viable and practical control group option for case-control studies.
• This method is particularly suitable for investigating breast cancer risk factors unrelated to family cancer history.
• The findings support the use of hospital visitors as an alternative control source in epidemiological research.