Controlled clinical trials
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Control Clin Trials · Feb 2003
DSMB case study: decision making when a similar clinical trial is stopped early.
Two similarly designed, placebo-controlled clinical trials are fully accrued and following patients for safety and outcome data. One trial is stopped at a planned interim analysis by its data safety and monitoring board (DSMB) due to a statistically significant treatment benefit. The statisticians and DSMB of the other trial are informed of these results. What are the responsibilities of the statistical center? How should the DSMB deal with the situation if the data do not support the stopped trial? What should the patients be told concerning the results of the two trials when one trial continues and the other is stopped? This DSMB case study reports on such a situation for two randomized clinical trials of oral ganciclovir for the prevention of cytomegalovirus disease in HIV/AIDS patients.
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Power calculations are very important in the planning of a well-designed clinical trial. Sometimes there is limited information available before the trial, making it highly desirable to adjust the sample size after seeing actual trial data. ⋯ We show how to compute the p value and confidence interval for this two-stage procedure. If the original sample size is maintained, analysis of the data is the same as for a fixed sample procedure.
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Control Clin Trials · Aug 2002
The reporting of methodological factors in randomized controlled trials and the association with a journal policy to promote adherence to the Consolidated Standards of Reporting Trials (CONSORT) checklist.
The "Consolidated Standards of Reporting Trials" (CONSORT) was developed to improve the suboptimal reporting of randomized controlled trials (RCTs). However, little is known about the quality of reporting since this publication. We undertook an observational study to determine the quality of reporting key methodological factors in RCTs since the publication of the CONSORT statement and if a journal policy to promote adherence to the CONSORT checklist was associated with superior reporting. ⋯ The number of methodological factors reported was greater in CONSORT promoters than in journals not promoting CONSORT in both unadjusted (6.0 and 5.1, respectively, p-value = 0.03) and adjusted (6.4 and 4.8 of the 11 methodological factors, respectively, p-value = 0.0001) analyses. While journals that promote CONSORT demonstrate superior reporting of RCTs, persistent inadequacies in reporting remain. Until these inadequacies are resolved health-care providers will remain limited in their ability to make informed inferences about the validity of the studies upon which they base their clinical practice.
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Control Clin Trials · Jun 2002
Principles, organization, and operation of a DNA bank for clinical trials: a Department of Veterans Affairs cooperative study.
The mapping and sequencing of the human genome promises rapid growth in understanding the genetically influenced mechanisms that underlie human disease. To realize this promise fully, it is necessary to relate genetic information to clinical phenotypes. ⋯ Concerns about subjects' rights, informed consent, privacy, and ownership of genetic material require attention in the development of DNA banks. In this paper we describe one approach to the solution of these problems that was adopted by one clinical trials group, the Department of Veterans Affairs Cooperative Studies Program.
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Control Clin Trials · Oct 2001
Comparative StudyComparison of the two-sided single triangular test to the double triangular test.
Comparative clinical trials are designed to determine whether a new treatment has either superior or different efficacy than a standard, that is, if theta represents a measure of treatment difference, to test the null hypothesis H(0): theta = 0 against the alternative hypothesis H(1) of either superior (theta > 0, one-sided) or different (theta not equal 0, two-sided with H(1)(+): theta > 0 and H(-)(1): theta < 0) efficacy. The triangular test (TT), a group sequential method, allows for early stopping of such trials. Its one-sided version (single TT) and two-sided version (double TT) were implemented in the first release of PEST software. ⋯ The statistical properties of the SSD and double TT were perfectly similar under all hypotheses. The modified single TT was underpowered as compared to the two others (the probability of falsely accepting H(0) strictly under H(-)(1) was 0.65 instead of 0.05), but the average sample number function was lower than the one of the double TT under all H(-)(1) hypotheses (-56% strictly under H(-)(1)). We conclude that the modified single TT offers a two-sided conclusion with many fewer patients than the double TT, but at the expense of a strong decrease in power under H(-)(1).