Harm

Exposure

Outcome

Eligible patients

Choice or happenstance

No exposure

Outcome

Prognosis

Patients at risk

Prognostic factor

Time

Develop target outcome

Do not develop target outcome

Develop target outcome

Do not develop target outcome

FIGURE 1-1. Clinical design of studies for core clinical questions.

For our case scenario, trials using histamine-2-receptor antagonists indicate that the clinical benefit for reducing recurrent bleeding may not be significantly greater than placebo. However, several trials examining proton pump inhibitors (PPI) do indicate a potential to reduce rebleeding. The most promising of these is by Lau and colleagues (2000) who examined the use of an intravenous (IV) PPI after endoscopic treatment of high risk peptic ulcer lesions, just as in our case scenario. The methods of this study indicate that it was a randomized controlled, double blind trial with concealed allocation, well-defined primary and secondary endpoints, and complete follow-up. It is appropriately powered for the primary endpoint (recurrent bleeding), and the results are reported in an intention to treat fashion, minimizing potential bias due to patient withdrawals or exclusions. The study results indicate a significant decrease in the incidence of recurrent peptic ulcer bleeding after endoscopic treatment, as well as shorter hospital stays and fewer transfusions, as a result of IV PPI administration.

Statistical Analysis

Appropriate statistical analysis is an integral part of any clinical trial in terms of the magnitude of the observed effect and the accuracy of the results. Differences in treatment effect are typically described as relative benefit increase and absolute benefit increase or relative risk reduction (RRR) and absolute risk reduction (ARR). The formulas for RRR and ARR are shown in Table 1-2. The RRR is the risk of the target outcome in one treatment group relative to the risk

Constipation Prescription

Constipation Prescription

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