Bisphosphonates and mortality: confounding in observational studies?

Residual confounding in observational studies.

To the Editor:—I read the study by Fellahi JL et al. titled “Perioperative use of dobutamine in cardiac surgery and adverse cardiac outcome” with great interest. This study showed that the use of dobutamine was associated with adverse outcomes in adult cardiac surgery, and the authors concluded that these results suggest that dobutamine should only be administered when the benefit is judged to ...

Confounding in Observational Studies Explained

Practical and ethical constraints mean that many clinical and/or epidemiological questions cannot be answered through the implementation of a randomized controlled trial. Under these circumstances, observational studies are often required to assess relationships between certain exposures and disease outcomes. Unfortunately, observational studies are notoriously vulnerable to the effect of diffe...

Residual Confounding in Observational Studies

To the Editor:—I read the study by Fellahi JL et al. titled “Perioperative use of dobutamine in cardiac surgery and adverse cardiac outcome” with great interest. This study showed that the use of dobutamine was associated with adverse outcomes in adult cardiac surgery, and the authors concluded that these results suggest that dobutamine should only be administered when the benefit is judged to ...

Confounding Equivalence in Observational Studies

Assessment and control for confounding by indication in observational studies.

In the evaluation of pharmacologic therapies, the controlled clinical trial is the preferred design. When clinical trial results are not available, the alternative designs are observational epidemiologic studies. A traditional concern about the validity of findings from epidemiologic studies is the possibility of bias from uncontrolled confounding. In studies of pharmacologic therapies, confoun...