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At least 307 records · Page 17Linked to original sources
PubMedDate not supplied

Large trials vs meta-analysis of smaller trials: how do their results compare?

OBJECTIVE: To evaluate the results of large clinical trials vs the pooled results of smaller trials. DATA IDENTIFICATION: Meta-analyses with at least 1 "large" study were identified from the Cochrane Pregnancy and Childbirth Database and from MEDLINE (1966-1995). STUDY SELECTION: We used a sample size approach to select 79 meta-analyses with at least 1 large study of 1000 or more patients. We used a statistical power approach to select 61 meta-analyses with at least 1 large study based on statistical power considerations. DATA EXTRACTION: The outcome of interest for each meta-analysis was the primary one stated in the original publication or, when not clearly specified, was decided on clinically. DATA SYNTHESIS: By random effects calculations, we found agreement between large and smaller trials in 90% of the meta-analyses selected by the sample size approach and in 82% of the meta-analyses selected by the statistical power approach. Twice as many disagreements appeared when the variability among large studies and among smaller studies was not considered (ie, fixed effects calculations). Of the 15 disagreements between results of large and smaller trials using the random effects model, plausible explanations were identified in 10 meta-analyses: 5 with differences in the control rate of events between large and smaller trials, 4 with specific protocol or study differences, and 1 with potential publication bias. Two other disagreements were not clinically important, and tentative reasons could be identified for 2 of the remaining 3 disagreements. CONCLUSIONS: Results of smaller studies are usually compatible with the results of large studies, but discrepancies do occur even when the diversity among both large studies and smaller studies is considered. Clinically important differences without a potential explanation are extremely uncommon. Future research should further examine sources of heterogeneity between the results of large and smaller trials.

Bias↗
PubMed1993

Operational and policy considerations of data monitoring in clinical trials: the Diabetes Control and Complications Trial experience.

Many clinical trials incorporate a system for monitoring emerging data that utilizes a committee composed of individuals who are independent of the investigators conducting the study. Although this is a common practice, there is a paucity of publications examining the operating methods of these groups. This paper describes the composition, functions, and procedures of the Data, Safety and Quality Review Group (DSQ) of the Diabetes Control and Complications Trial (DCCT). The DSQ is not masked to emerging data and the voting membership is made up of individuals with a wide diversity of expertise that reflects the needs of the trial. There are also nonvoting exofficio members who represent other components of the study organization. In addition to data monitoring, the DSQ provides external review of coordinating center operations. A distinctive aspect of the DCCT's DSQ is the creation of a free-standing operations manual for the DSQ's use during the trial and the involvement of the study investigators in developing certain sections of this document. Utilizing a process that allowed participation of the investigators was considered critical to achieving a mutual understanding regarding the planned uses and interpretations of the study data prior to the study's completion so as to minimize the chances of major disagreements regarding the conclusions drawn. Equally important, the existence of such a manual provides documentable reassurance to all interested parties that both scientific integrity and patient safety are being closely watched and gives the study investigators confidence that the results of the study will be scientifically credible and clinically important.

Clinical Trials as Topic↗
PubMed1996

The economic evaluation of the FIRST study: design of a prospective analysis alongside a multinational phase III clinical trial. Flolan International Randomized Survival Trial.

Prospective economic assessments of new pharmaceutical therapies are increasingly being incorporated into phase III clinical trials. We report on the design of an economic evaluation integrated into the Flolan International Randomized Survival Trial (FIRST). Economic evaluation was considered a critical component of the assessment of this therapy given the resources required to administer epoprostenol (Flolan), a therapy that would require lifelong continuous intravenous infusion. Economic secondary endpoints were incorporated in the clinical trial. The economic evaluation of the treatment was integrated into all aspects of study development, including study design, implementation, and monitoring. Since this was a multinational trial, special care was required to ensure that the protocol design was appropriate for all study countries. The economic assessment required the development of several methodologic components: a set of background economic concepts to guide protocol development, a set of resource items to be recorded when required for study participants; a set of data collection instruments for assessment of health-related quality of life for study patients; and a protocol for a resource costing exercise for the study. We report the data elements included in the study design, as well as a discussion of some of the issues faced in developing the economic evaluation for this trial.

Antihypertensive Agents↗
PubMed2004

Rationale and design of the GISSI heart failure trial: a large trial to assess the effects of n-3 polyunsaturated fatty acids and rosuvastatin in symptomatic congestive heart failure.

BACKGROUND: The GISSI Heart Failure project is a large-scale, randomized, double-blind study designed to investigate the effects of n-3 polyunsaturated fatty acids and rosuvastatin on mortality and morbidity in patients with symptomatic heart failure. METHODS AND RESULTS: Patients with New York Heart Association classes II to IV heart failure, already receiving optimized recommended therapy, will be recruited in a nation-wide network of more than 300 cardiology and internal medicine services to be randomly allocated to treatment with n-3 polyunsaturated fatty acids (1 g daily) or the corresponding placebo. Patients with no clear indication or contraindication to cholesterol-lowering therapy will be further randomized to receive low-dose rosuvastatin (10 mg daily) or placebo. According to data available in heart failure registries, it is expected that 70% of the patients will be suitable to enter both components of the trial, which assume the same co-primary endpoints: (a) 15% reduction of all-cause mortality and (b) 20% reduction of all-cause mortality or cardiovascular hospitalizations. The trial is event-driven and will continue either until at least 1252 deaths have been recorded or a reduction of all-cause mortality will satisfy the significance boundaries, which have been established to stop the study. The recruitment of the planned sample size of approximately 7000 patients randomized in the n-3 PUFA trial is expected to be completed within 18 months from the trial start. As of February 29, 2004, 4624 heart failure patients have been included in the trial. CONCLUSION: The GISSI-HF project, with its protocol articulated into two independent randomization schemes, has the aim and the power to verify the hypothesis that n-3 polyunsaturated fatty acids and rosuvastatin can favorably modify the prognosis of patients with symptomatic heart failure.

Fatty Acids, Omega-3↗
PubMedDate not supplied

Open trials as a method of prioritizing medications for inclusion in controlled trials for cocaine dependence.

This paper describes a rapid and systematic method of using open trials to identify medications that may be useful for the treatment of cocaine dependence. Results of these open trials can be used to prioritize medications for inclusion in subsequent double-blind, placebo-controlled trials. Preliminary results are presented from the evaluation of propranolol, nefazodone, and the combination of phentermine and fenfluramine (phen/fen). Each medication was evaluated in an open trial, and results were compared to results obtained from a group that received a multivitamin. Outcome measures included treatment retention, urine toxicology screens, self-reported cocaine use, and changes on the Addiction Severity Index (ASI). Treatment retention was significantly better in the propranolol group than in the multivitamin group. Concurrent alcohol abuse was associated with increased rates of attrition in the multivitamin group, and the phen/fen group, but not in the propranolol group. Neither the nefazodone nor the phen/fen groups showed any outcome advantages over the multivitamin group. We conclude that propranolol may enhance retention among cocaine-dependent patients, especially among those who also abuse alcohol. These results encourage a double-blind, placebo-controlled trial of propranolol.

Adult↗
PubMed1998

Influence of a randomized clinical trial on practice by participating investigators: lessons from the Coronary Angioplasty Versus Excisional Atherectomy Trial (CAVEAT). CAVEAT I and II Investigators.

OBJECTIVES: We sought to determine whether the results of the first Coronary Angioplasty Versus Excisional Atherectomy Trial (CAVEAT-I) influenced subsequent practice patterns among the investigators. BACKGROUND: CAVEAT-I demonstrated that directional coronary atherectomy (DCA) resulted in higher rates of early complications at a higher cost and with no clinical benefit. We sought to determine whether these results influenced subsequent use of procedures among CAVEAT-I investigators. METHODS: We compared the results of a week-long registry of all coronary interventions performed at 35 CAVEAT-I sites in 1994 with those of a similar registry obtained in 1992 before the trial, the results of which were published in 1993. For control purposes, the use of procedures was studied at 24 additional sites to provide insight into practice at hospitals not participating in the trial. A total of 1,465 interventions were analyzed. RESULTS: Ninety-four percent of CAVEAT-I sites responded. Utilization rates differed between CAVEAT-I and CAVEAT-I follow-up (p < 0.001). Balloon angioplasty decreased from 83.8% to 68.5%, DCA increased slightly from 10.7% to 14.1%, and the use of other devices increased from 5.4% to 17.5%. Stand-alone balloon use was more prevalent at nonparticipating control sites than at sites that took part in CAVEAT-I (p < 0.001). CONCLUSIONS: Paradoxically, despite the negative findings of CAVEAT-I, there was a noteworthy trend toward an increase in the use of DCA and other devices at CAVEAT-I sites. Our findings suggest that among investigators in the trial, there may have been a lack of influence of trial data on clinical practice patterns 1 year after publication of the results. Ethics of protocol: Both CAVEAT I and II were approved by the Institutional Review Board at each study site.

Adult↗
PubMed1988

A randomized clinical trial of total parenteral nutrition in malnourished surgical patients: the rationale and impact of previous clinical trials and pilot study on protocol design.

The rationale for a large-scale clinical trial of preoperative total parenteral nutrition (TPN) is described in the context of previous clinical trials that have attempted to demonstrate reduction of operative morbidity with preoperative TPN. Defects in study design or execution potentially compromising the validity of these studies are analyzed. Results of a single-institution pilot study performed during the planning phase of the multiinstitutional preoperative TPN trial are presented. This literature review and pilot study provided the data necessary to permit appropriate design of many critical elements in the protocol for the clinical trial including sample size, eligibility criteria, duration and intensity of treatment regimens, and end-point criteria. The rationale underlying critical decisions in protocol design are presented in detail to allow more meaningful interpretation of the results of the clinical trial.

Clinical Trials as Topic↗
PubMed2003

UK Back pain Exercise And Manipulation (UK BEAM) trial--national randomised trial of physical treatments for back pain in primary care: objectives, design and interventions [ISRCTN32683578].

BACKGROUND: Low back pain has major health and social implications. Although there have been many randomised controlled trials of manipulation and exercise for the management of low back pain, the role of these two treatments in its routine management remains unclear. A previous trial comparing private chiropractic treatment with National Health Service (NHS) outpatient treatment, which found a benefit from chiropractic treatment, has been criticised because it did not take treatment location into account. There are data to suggest that general exercise programmes may have beneficial effects on low back pain. The UK Medical Research Council (MRC) has funded this major trial of physical treatments for back pain, based in primary care. It aims to establish if, when added to best care in general practice, a defined package of spinal manipulation and a defined programme of exercise classes (Back to Fitness) improve participant-assessed outcomes. Additionally the trial compares outcomes between participants receiving the spinal manipulation in NHS premises and in private premises. DESIGN: Randomised controlled trial using a 3 x 2 factorial design. METHODS: We sought to randomise 1350 participants with simple low back pain of at least one month's duration. These came from 14 locations across the UK, each with a cluster of 10-15 general practices that were members of the MRC General Practice Research Framework (GPRF). All practices were trained in the active management of low back pain. Participants were randomised to this form of general practice care only, or this general practice care plus manipulation, or this general practice care plus exercise, or this general practice care plus manipulation followed by exercise. Those randomised to manipulation were further randomised to receive treatment in either NHS or private premises. Follow up was by postal questionnaire one, three and 12 months after randomisation. The primary analysis will consider the main treatment effects before interactions between the two treatment packages. Economic analysis will estimate the cost per unit of health utility gained by adding either or both of the treatment packages to general practice care.

Adult↗
PubMed2005

Impact of cigarette smoking in high-risk patients participating in a clinical trial. A substudy from the Heart Outcomes Prevention Evaluation (HOPE) trial.

BACKGROUND: In recent large cardiovascular trials done in stable patients, 14-31% of the participants were smokers; the consequences of smoking in these trials using medications known to reduce cardiovascular events, have not been assessed. DESIGN: We evaluated the cardiovascular outcomes according to smoking status of men and women participating in the Heart Outcomes Prevention Evaluation trial. METHODS: The occurrence of cardiovascular events was documented among participants who did not change their smoking status during the trial. There were 2728 'never smokers', 5241 'former smokers' and 936 'current smokers', and all had stable cardiovascular disease or diabetes with at least one other risk factor. None had previous congestive heart failure or known left ventricular ejection fraction < 0.40. RESULTS: During the 4.5-year follow-up, there were 641 cardiovascular deaths, 978 myocardial infarctions, 358 strokes and 1021 deaths. In comparison to 'never smokers', smokers had relative risks adjusted for confounding variables including medications known to reduce cardiovascular mortality and morbidity, for cardiovascular death of 1.65 [95% confidence interval (CI), 1.28-2.14], for myocardial infarction of 1.26 (95% CI, 1.01-1.58), for stroke of 1.42 (95% CI, 1.00-2.04), and for total mortality of 1.99 (95% CI, 1.63-2.44). The rates of these events among 'former smokers' were not different from those of 'never smokers'. CONCLUSIONS: Smoking increased the risk of mortality and morbidity among high-risk patients despite the use of medications known to reduce cardiovascular events. Smoking cessation programs should be reinforced even for patients participating in clinical trials.

Aged↗