ISSN:0277-6715    

DOI:10.1002/sim.4780060702

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780060703

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe replicate variability of meta‐analyses of controlled clinical trials has been assessed as a measure of scientific precision. 46 of 91 known meta‐analysis papers were divided into 20 cohorts of studies of the same therapies. Ten cohorts contained meta‐analyses with different statistical conclusions; 14 contained differing clinical conclusions with a wider spread than the statistically differing studies. Possible causes of variability, such as different trials included, different policies regarding the inclusion of non‐randomized and unpublished trials, and different statistical methodologies, were not obvious causes of differing conclusions. Further work in this area should include multivariate analyses in order to explore possible interactions in the factors accounting for the variability found in replicate meta

ISSN:0277-6715    

DOI:10.1002/sim.4780060704

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThose who report a clinical trial should acknowledge the right of the ‘consumer’ to make decisions based on his own valuation of the beneficial and adverse effects which rival treatments may have. Suppose a new patient is inclined to trade one unit of benefit forcunits of complication. Then he should (should not) be given the treatment if his estimated utility gain,χ1‐cχ2, is positive (negative) and statistically significant according to the data of the trial: hereχ1(χ2) denotes the observed average benefit (complication level). If the estimated gain is not statistically significant, the data do not allow any firm recommendation. This c‐dependent recommendation in general cannot be determined from inspection of a joint confidence region for the two means concerned. Therefore investigators should present the outcome of the significance test as a function ofc(inverted inference). Typically there are several types of adverse effect or benefit, in which case the quantitycmust be generalized into a vector of personal relative util

ISSN:0277-6715    

DOI:10.1002/sim.4780060705

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractMonitoring interim accumulating data in a clinical trial for evidence of therapeutic benefit or toxicity is a frequent policy, usually carried out by an independent scientific committee. Repeated testing at conventional critical values can substantially inflate the type I error rate. To maintain acceptable levels, group sequential and stochastic curtailment have been developed for clinical trials. One should not view such methods as absolute rules, but as useful guides. The decision process to terminate a trial early is complex and necessitates an accounting for many factors. The Beta‐Blocker Heart Attack Trial provides an excellent example of many of these issue

ISSN:0277-6715    

DOI:10.1002/sim.4780060706

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe increased interest of the public and the medical profession in complementary forms of therapy introduces an urgent need for proper assessment of efficacy. This growth in popularity suggests that complementary therapies are effective in some circumstances, but without objective assessment neither the public nor the medical profession can be sure. Rigorous scientific assessment is required, but the nature of complementary therapy is such that double‐blind randomized controlled trials, as usually conducted, are rarely applicable, and alternative approaches are needed. At its best, complementary therapy is designed individually for each patient, and few treatments can readily be applied ‘blind’. These are the main problems in trial design but complementary therapists are also aware of the importance of body‐mind interactions: they see the ‘placebo effect’ as an integral part of treatment which needs investigation, and they question the validity of clinical trials in which the patient's will is not fully engaged through lack of information, and of those not asking the patients if they feel better. The problems are examined and alternative approaches suggested. The paper raises the question of whether they areonlyproblems for complementa

ISSN:0277-6715    

DOI:10.1002/sim.4780060707

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractWe consider several sources of heterogeneity in a clinical trial with patients' survival time as the main response criterion: differences in prognosis which can be attributed to a latent or ignored prognostic factor; differences in treatment efficacy in subgroups of patients, and differences in treatment combinations received by the patients. The impact of these types of heterogeneity on the treatment comparison is studied assuming a proportional hazards model. It is measured by the size and power of the logrank and proportional hazards score tests and by the bias of the estimated treatment effect. We show that heterogeneity can seriously affect the treatment comparison and has to be considered during the planning stage as well as at the analysis of a clinical trial.

ISSN:0277-6715    

DOI:10.1002/sim.4780060708

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractOver the past 20 years, mortality rates from uterine cervix carcinoma have been decreasing owing to earlier diagnosis and improved treatment. The incidence of secondary effects from radiation therapy has spurred some interest and injuries resulting from ‘over’‐treatment have been of some concern. The present study concerns the evaluation of bowel complications following treatment for the 272 stage IIb and III patients treated in our centre between 1967 and 1973. Competing risk methodology is applied and the influence of radiotherapy parameters is evaluated by a log‐linear model of the event‐specific failure rates. A single parameter (NSD) which summarizes total dose, total number of sessions and total treatment time is found to be related to the occurrence of comp

ISSN:0277-6715    

DOI:10.1002/sim.4780060709

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractWe designed a randomized clinical trial to determine the efficacy of plasma exchange in Guillain‐Barré syndrome, an acute neurological disease leading to paralysis in previously healthy subjects. Some patients require temporary mechanical ventilation during the course of the disease. Ventilatory status was analysed using a three‐state model with a transient state defined by use of temporary mechanical ventilation, and the probability of being mechanically ventilated modelled as a function of time since randomization. The plot of this function reflects the effect of plasma exchange on ventilatory status showing that fewer plasma‐exchanged patients than controls required ventilatory assistance and that the duration of assistance was shorter. Similar functions can be used in a more general framework when the response criterion includes a transient

ISSN:0277-6715    

DOI:10.1002/sim.4780060710

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractIn this paper we present a method of teaching medical students a logical approach to diagnosis. By using the independent Bayes method, commonly employed in decision aids, students can be made aware of how information on each new symptom affects what is likely in the light of what is known already. This approach is used for the diagnosis of thoracic symptoms in patients with normal chest X‐rays and an example is given. Extensions of the system to incorporate information from investigations and error costs are discusse

ISSN:0277-6715    

DOI:10.1002/sim.4780060711

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY