Study Design And Bias Practice Test

A randomized trial compares a new long-acting insulin to standard basal insulin. The study is open-label, and clinicians intensify background therapy more aggressively in the new-insulin arm because they believe it is superior, which may influence A1c outcomes. Which methodological improvement would reduce bias in this study?

A case-control study evaluates whether prior use of over-the-counter (OTC) proton pump inhibitors (PPIs) is associated with Clostridioides difficile infection. Cases (C. difficile positive) and controls (C. difficile negative) are asked to recall OTC PPI use over the past 6 months, and cases are more likely to remember and report OTC products after being counseled on potential causes. What type of bias could affect the validity of this study?