PubMed · 16267923
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S Srinivasan. 1998. Physician, do no harm.. https://pubmed.ncbi.nlm.nih.gov/16267923/
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Three-arm trials including an experimental treatment, an active control and a placebo group are frequently preferred for the assessment of non-inferiority. In contrast to two-arm non-inferiority studies, these designs allow a direct proof of efficacy of a new treatment by comparison with placebo. As a further advantage, the test problem for establishing non-inferiority can be formulated in such a way that rejection of the null hypothesis assures that a pre-defined portion of the (unknown) effect the reference shows versus placebo is preserved by the treatment under investigation. We present statistical methods for this study design and the situation of a binary outcome variable. Asymptotic test procedures are given and their actual type I error rates are calculated. Approximate sample size formulae are derived and their accuracy is discussed. Furthermore, the question of optimal allocation of the total sample size is considered. Power properties of the testing strategy including a pre-test for assay sensitivity are presented. The derived methods are illustrated by application to a clinical trial in depression.
BACKGROUND: Currently, the two most common surgical techniques for approaching the vas during vasectomy are the incisional method and the no-scalpel technique. Whereas the conventional incisional technique involves the use of a scalpel to make one or two incisions, the no-scalpel technique uses a sharp-pointed, forceps-like instrument to puncture the skin. The no-scalpel technique aims to reduce adverse events, especially bleeding, bruising, hematoma, infection and pain and to shorten the operating time. OBJECTIVES: The objective of this review was to compare the effectiveness, safety, and acceptability of the incisional versus no-scalpel vasectomy approach to the vas. SEARCH STRATEGY: We searched the computerized databases of CENTRAL, MEDLINE, EMBASE, POPLINE and LILACS in May 2006. In addition, we searched the reference lists of relevant articles and book chapters. SELECTION CRITERIA: Randomized controlled trials and controlled clinical trials were included in this review. No language restrictions were placed on the reporting of the trials. DATA COLLECTION AND ANALYSIS: We assessed all titles and abstracts located in the literature searches and two authors independently extracted data from the articles identified for inclusion. Outcome measures included safety, acceptability, operating time, contraceptive efficacy, and discontinuation. MAIN RESULTS: Two randomized controlled trials evaluated the no-scalpel technique and differed in their findings. The larger trial demonstrated less perioperative bleeding (Odds ratio (OR) 0.49; 95% Confidence Interval (CI) 0.27 to 0.89) and pain during surgery (OR 0.75; 95% CI 0.61 to 0.93), scrotal pain (OR 0.63; 95% 0.50 to 0.80), and incisional infection (OR 0.21; 95% CI 0.06 to 0.78) during follow up than the standard incisional group. Both studies found less hematoma with the no-scalpel technique (OR 0.23; 95% CI 0.15 to 0.36). Operations using the no-scalpel approach were faster and had a quicker resumption of sexual activity. The smaller study did not find these differences; however, the study could have failed to detect differences due to a small sample size as well as a high loss to follow up. Neither trial found differences in vasectomy effectiveness between the two approaches to the vas. AUTHORS' CONCLUSIONS: The no-scalpel approach to the vas resulted in less bleeding, hematoma, infection, and pain as well as a shorter operation time than the traditional incision technique. Although no difference in effectiveness was found between the two approaches, the sample sizes might have been too small to detect actual differences. Additional well-conducted randomized trials would help answer this question.
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