Randomized trial results relative risk reduction

A second meta-analysis was based on data from individual patients in five long-term randomized trials, which assessed ACE inhibitors in 12,763 patients with left ventricular dysfunction or heart failure. The relative risk reduction of death, with a follow-up period exceeding 4 years, is 20% (13-26%). This means it is necessary to treat 26 patients for 5 years (95 % Cl 19-41) to avoid one death. If the combined end point used to assess the results is death plus reinfarction plus hospitalization for heart failure, it is necessary to treat 14 patients for 4 years to avoid one such event (95% Cl 12-18). 

Only one observational study, conducted in an elderly retirement community, showed an elevated CRC risk with daily aspirin use. Two additional studies showed little or no effect. In one, aspirin taken at a dose of 325 mg every other day produced no evidence of reduced risk in a relatively low-risk population. In another study, the apparent benefit did not reach significance until self-medication with aspirin had been employed for over 20 years. The results of these studies indicated the need for a formal, randomized, controlled trial of sufficient pqwer to elicit a significant result, but this would be a large undertaking. The only known primary prevention study of which we are aware is the Women s Health Initiative. This study involved 16,608 patients who were followed over an average of 5.2 years. The result showed a 37% risk reduction of CRC, comparable to that anticipated with NSAIDs. The increased cardiovascular risk, however, makes this option nonviable. ... 

A field clinical trial conducted in Isfahan, Iran, to determine the effectiveness of deet sticks against leishmaniasis in 430 students (50% male, 50% female) did not demonstrate any treatment effect." The intervention was reported to be effective for 18-20 hours, and its minimum effective concentration was 55-77 pg/cm. Deet placebo was randomized to 330 individuals and placebo stick was randomized to 100 controls, and the treatment allocation code of sticks was revealed only at the end of the study. The children were followed up for 10 months. The efficacy of these sticks was evaluated in terms of the reduction in infection by leishmaniasis using relative risk (RR). Confusingly, in the results section of the study the investigators reported a different number of treatments and controls out of 200 students who were protected using the placebo pen 2 students acquired leishmaniasis, and out of 230 students who were protected using the deet pen 8 students acquired leishmaniasis. Thus, the study cannot be accurately interpreted. 

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