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C L Meinert

Publications and source records attributed to C L Meinert.

At least 55 records · Page 3Linked to original sources
PubMed1984

Linear regression analysis of binary response data with mixed covariates - a simulation study.

In a clinical trial with binary outcome, analyses are required for treatment or study group comparisons adjusted for covariate effects. A special problem arises with "mixed binary and Gaussian covariates", i.e., when some covariates are binary and some are continuous and may be assumed to be Gaussian. The correct model for such a data structure is of the logistic form. In the past, analyses of such data have been carried out by linear regression as well as by logistic regression methods. In this article, computer simulation was used to study the type I error level of linear regression analysis tests for treatment comparisons, when applied to a binary outcome variate obeying a logistic model with mixed binary and Gaussian covariates. It was found that the true type I error level depends on the distribution of covariates among treatment groups and on the magnitudes of the actual covariate effects, and can differ importantly from that assumed under Gaussian theory. Some recommendations are made for developing computer package programs for this problem.

Clinical Trials as Topic↗
PubMed1984

Content of reports on clinical trials: a critical review.

A 10% sample of English language papers, published in 1980, listed in Index Medicus, and classified under the heading, Clinical Trials, was used to assess the state of trials and reports from them. Tabulations are presented concerning the design of the trials represented by the papers in the sample. The manuscript concludes with a discussion of reporting responsibilities for investigators involved in trials and of methods for meeting those responsibilities.

Clinical Trials as Topic↗
PubMed1982

Funding for clinical trials.

This paper provides a review of available funding sources for clinical trials, with emphasis on trials funded via the National Institutes of Health. Data from the NIH Inventory of Clinical Trials are used to summarize the cost and key design characteristics of NIH trials. The paper concludes with a discussion of some of the factors which add to the cost of trials.

Clinical Trials as Topic↗
PubMed1981

On the detection of outlier clinics in medical and surgical trials: I. Practical considerations.

In the conduct of multicenter clinical trials, comparisons among the clinical centers are often made with respect to such measures as incidence of diagnosis of various events, operative mortality (in the case of a surgical trial), and patient adherence of the treatment regimen. If one or two clinics seem to stand out from all the other clinics with respect to any such measures, this may indicate - among other things - differences in skill levels or possible deficiencies in understanding and following the protocol among these clinics. On the other hand, when clinics are ranked on any measure, one clinic must of necessity be first and one last; thus, it is necessary to determine whether the extreme values represent true differences from the values of the other clinics or whether they can be attributed to random variation alone. A statistical test is described for detecting clinics that are outliers - i.e., truly different from all the rest of the clinics in the trial. Critical values for this test are given for various numbers of clinics, numbers of patients enrolled per clinic, and probabilities of a patient incurring a given event under the null hypothesis of no differences among the clinics. Use of this test in detecting outlier clinics with respect to incidence of various endpoints is illustrated for the case of a large, multicenter drug trial.

Clinical Trials as Topic↗
PubMed1981

On the detection of outlier clinics in medical and surgical trials: II. Theoretical considerations.

In the conduct of multicenter clinical trials, comparisons among the clinical centers are often made with respect to such measures as incidence of diagnosis of various events, operative mortality, and patients adherence to the treatment regimen. Slippage and outlier tests for statistically identifying clinics that are outliers - that is, truly different from the rest of the clinics - with respect to such measures are described. Critical values obtained for these tests by computer simulation are given for various numbers of clinics, numbers of patients enrolled per clinic, and probabilities (p) of a patient incurring a given event under the null hypothesis of no differences among the clinics. Previously published critical values based on normally distributed response variables are applicable only for p close to 0.5. The slippage and outlier tests are compared with respect to statistical power. Alternative forms of the slippage test based on the angular transformation and on hypergeometric probabilities are considered.

Clinical Trials as Topic↗
PubMed1981

Organization of multicenter clinical trials.

The typical multicenter trial involves several clinical centers, a data center, and other specialty centers as well. A common structure for large-scale trials funded by the National Institutes of Health (NIH) involves two or three key committees. One of these is comprised exclusively of investigators from the study (steering committee) and is responsible for operation of the trial. A second committee, usually comprised of individuals not involved in the study, is responsible for overseeing the trial and providing advice to the NIH regarding the study. A third committee--sometimes part of the second committee and comprised largely of individuals not involved in the trial--is responsible for monitoring the study results for evidence of adverse or beneficial treatment effects as the trial proceeds. The organizational design of a trial may be as important as the experimental design is in the success of the trial. Attention to organizational questions at the start of the study and periodic review and revision of the structure as the trial proceeds can help identify problems before they become major impediments to progress in the trial. Such ongoing monitoring and periodic review is especially important in the long-term multicenter trial.

Centralized Hospital Services↗
PubMed1980

Toward more definitive clinical trials.

The randomized clinical trial is an essential evaluation tool in the health care field. Unfortunately, the majority of trials performed have too few patients to reach a conclusion regarding the treatments under study. In many instances, the multicenter trial represents the only way to obtain the necessary numbers. Such trials are difficult to organize and costly to carry out, but they have strengths not found in the ordinary single center trial. The multiplicity of disciplines required usually leads to better design and more careful execution than can be achieved with the resources of a single center. The heterogeneity of the population and multiplicity of clinics applying the study treatments provide a more realistic test of the therapies in question than is possible in a single clinic. Sponsors of trials need to stimulate more research into the methodology of multicenter trials, including investigation of the methods of organizing and carrying out such trials in a cost-effective manner. In addition, a communications network should be developed to promote the field of clinical trials as a discipline and to facilitate the identification and dissemination of information on their design and conduct.

Clinical Trials as Topic↗
PubMed1979

Communications: Should mechanisms be established for sharing among clinical trial investigators experiences in handling problems in design, execution, and analysis? Methodology: the case for improved communications.

Despite their long history, the number that are in operation now, and the current level of expenditures on them, clinical trials have not been the focus of sufficient methodologic research. The paucity of metholologic explorations is further aggravated by the constraints on communications regarding methodology. Those individuals working in the area of clinical trials need to establish some professional identity with the field. Methodology in the areas of design and management of clinical trials needs to be stimulated, perhaps through special requests for applications (RFAs) and requests for proposals (RFPs). Communications could be improved by the establishments of a professional society, the development of an appropriate journal, and establishment of national training and information centers for clinical trials.

Clinical Trials as Topic↗
PubMed1975

A plea for a discipline of health and medical evaluation.

There is an expanding need for quantitative information to evaluate health and medical care procedures. Existing methods for designing and carrying out evaluation studies need to be improved to provide better techniques for answering questions on efficacy of health and medical procedures, and in providing a more adequate information base on which to set healthy policy. This paper reviews some of the problems in the design and conduct of evaluation research, and makes a plea for creation of a special discipline to support and develop the field of health and medical care evaluation.

Clinical Trials as Topic↗