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Review Question - QID 109566

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QID 109566 (Type "109566" in App Search)
A group of investigators seeks to compare the non-inferiority of a new angiotensin receptor blocker, salisartan, with losartan for reduction of blood pressure. 2,000 patients newly diagnosed with hypertension are recruited for the trial; the first 1,000 recruited patients are administered losartan, and the other half are administered salisartan. Patients with a baseline systolic blood pressure less than 100 mmHg are excluded from the study. Blood pressure is measured every week for four weeks, with the primary outcome being a reduction in systolic blood pressure by salisartan within 10% of that of the control. Secondary outcomes include incidence of subjective improvement in symptoms, improvement of ejection fraction, and incidence of cough. 500 patients withdraw from the study due to symptomatic side effects. In an intention-to-treat analysis, salisartan is deemed to be non-inferior to losartan for the primary outcome but inferior for all secondary outcomes. As the investigators launch a national advertising campaign for salisartan, independent groups report that the drug is inferior for its primary outcome compared to losartan and associated with respiratory failure among patients with pulmonary hypertension. How could this study have been improved?

Increased study duration

5%

3/66

Posthoc analysis of primary outcome among patients who withdrew from study

15%

10/66

Randomization

14%

9/66

Retrial of primary outcome for clinical effectiveness instead of non-inferiority

21%

14/66

Increased sample size

14%

9/66

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This question presents a controlled, non-inferiority trial for a medication that is deemed to be non-inferior to the control medication. This study's methodology can be improved by randomizing patients to reduce the possibility of confounders.

A confounder is a factor that is either positively or negatively associated with both the exposure and outcome. Confounders are not in the causal pathway, but not adjusting the analysis for confounding can distort the true association and lead to false conclusions. In order for randomization to effectively balance out the effect of confounding factors, one assumes that the study sample size is large enough and that both the investigators and patients are blinded to the identity of the intervention.

Incorrect Answers:
Answer 1: Increased study duration would improve the trial's analysis for its primary outcome and improve its documentation of the drug's side effects, but it would not minimize the potential for confounding. A non-randomized study presents more concerns for interpreting the results.

Answer 2: Posthoc analysis of the primary outcome among patients who withdrew from the study would be unnecessary because the analysis was already conducted as an intention-to-treat analysis. This means that patients who withdrew from the study are still counted in their original study group during the final analysis.

Answer 4: Retrial of primary outcome for clinical effectiveness instead of non-inferiority may further strengthen these investigators' argument (and sales pitch) for salisartan but would be expensive and time-consuming. Furthermore, the secondary outcome of subjective improvement of symptoms was already inferior, decreasing the yield of a retrial under similar conditions.

Answer 5: Increased sample size would strengthen the statistical precision of the trial analysis (i.e., p-value), but it would not decrease the potential for confounding. Given the large sample size, it is more important to randomize the participants then to recruit more.

Bullet Summary:
Confounding in prospective clinical research can be minimized by randomization.

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