Study designs — MCQs

A research team has data from three completed studies on statin use and Alzheimer's disease: Study A (case-control, OR=0.6, n=500), Study B (retrospective cohort, RR=0.7, n=10,000), and Study C (RCT with cognitive decline as secondary endpoint, RR=0.9, n=2,000). The case-control study used prevalent cases, the cohort study had significant loss to follow-up in the unexposed group, and the RCT was underpowered for cognitive outcomes. Synthesize the evidence to determine the most reliable conclusion about the association.

A public health department needs to determine whether a cluster of birth defects in a county is associated with industrial pollution. They have limited resources, the suspected exposure occurred 3-5 years ago, and the outcome is rare (15 cases identified). Multiple potential confounders exist including maternal age, socioeconomic status, and prenatal care access. The community demands rapid answers. Evaluate the most appropriate initial study design considering feasibility, ethics, and scientific validity.

A pharmaceutical company wants to evaluate a new anticoagulant's effectiveness in preventing stroke in atrial fibrillation patients. They have limited funding and need results within 2 years. The drug has promising phase 2 data. Concurrent medications and comorbidities vary widely in the target population. The company must choose between a pragmatic trial in 50 community hospitals or an explanatory trial at 3 academic centers with strict protocols. Evaluate which design best serves both scientific and practical objectives.

A randomized controlled trial of a new diabetes medication shows significant reduction in HbA1c levels (p<0.001). However, 40% of participants in the treatment group and 15% in the placebo group dropped out before study completion, primarily due to gastrointestinal side effects in the treatment group. The analysis includes only participants who completed the study. Analyze the impact on study conclusions.

A study follows 5,000 healthcare workers from 1995 to 2015, tracking their exposure to bloodborne pathogens and development of chronic infections. The researchers use employment records to determine exposure history rather than relying on participant recall. In 2010, the hospital implemented a new electronic medical record system that improved documentation of needle-stick injuries. Analyze how this change affects the validity of the exposure assessment.