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Reassessment Method (reassessment + method)

Distribution by Scientific Domains
Medical Sciences50%

Kinds of Reassessment Method

  • continual reassessment method
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    Selected Abstracts

    Continual Reassessment Method for Ordered Groups

    BIOMETRICS, Issue 2 2003
    John O'Quigley
    Summary We investigate the two-group continual reassessment method for a dose-finding study in which we anticipate some ordering between the groups. This is a situation in which, for either group, we have little or almost no knowledge about which of the available dose levels will correspond to the maximum tolerated dose (MTD), but we may have quite strong knowledge concerning which of the two groups will have the higher level of MTD, if indeed they do not have the same MTD. The motivation for studying this problem came from an investigation into a new therapy for acute leukemia in children. The background to this study is discussed. There were two groups of patients: one group already received heavy prior therapy while the second group had received relatively much lighter prior therapy. It was therefore anticipated that the second group would have an MTD higher or at least as high as the first. Generally, likelihood methods or, equivalently, the use of noninformative Bayes priors, can be used to model the main aspects of the study, i.e., the MTD for one of the groups, reserving more informative Bayes modeling to be applied to the secondary features of the study. These secondary features may simply be the direction of the difference between the MTD levels for the two groups or, possibly, information on the potential gap between the two MTDs. [source]

    Learning from previous responses in phase I dose-escalation studies

    BRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 1 2001
    John Whitehead
    Dose escalation in phase I studies is generally performed on the basis of clinical experience and judgement. In this paper some of the statistical approaches that have been proposed for the formalization of the procedure are described. Apart from the use of the Continual Reassessment Method in oncology studies, such formal methods have received little implementation. The purpose of presenting them here is to promote their further exploration and appropriate implementation. Certain limitations are discussed, which will be best overcome by collaboration between clinical pharmacologists and statisticians. [source]

    Systematic evaluation of the highest current threshold for regional anaesthesia in a porcine model

    ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2010
    T. STEINFELDT
    Background: The purpose of this study was to determine systematically the highest minimal stimulation current threshold for regional anaesthesia in pigs. Methods: In an established pig model for regional anaesthesia, needle placements applying electric nerve stimulation were performed. The primary outcome was the frequency of close needle to nerve placements as assessed by resin injectates and subsequent anatomical evaluation. Following a statistical model (continual reassessment method), the applied output currents were selected to limit the necessary number of punctures, while providing guidance towards the highest output current range. Results: Altogether 186 punctures were performed in 11 pigs. Within the range of 0.3,1.4 mA, no distant needle to nerve placement was found. In the range of 1.5,4.1 mA, 43 distant needle to nerve placements occurred. The range of 1.2,1.4 mA was the highest interval that resulted in a close needle to nerve placement rate of ,95%. Conclusions: In the range of 0.3,1.4 mA, all resin deposition was found to be adjacent to nerve epineurium. The application of minimal current intensities up to 1.4 mA does not obviously lead to a reduction of epineural injectate contacts in pigs. These findings suggest that stimulation current thresholds up to 1.4 mA result in equivalent needle tip localisation in pigs. [source]

    Continual Reassessment Method for Ordered Groups

    BIOMETRICS, Issue 2 2003
    John O'Quigley
    Summary We investigate the two-group continual reassessment method for a dose-finding study in which we anticipate some ordering between the groups. This is a situation in which, for either group, we have little or almost no knowledge about which of the available dose levels will correspond to the maximum tolerated dose (MTD), but we may have quite strong knowledge concerning which of the two groups will have the higher level of MTD, if indeed they do not have the same MTD. The motivation for studying this problem came from an investigation into a new therapy for acute leukemia in children. The background to this study is discussed. There were two groups of patients: one group already received heavy prior therapy while the second group had received relatively much lighter prior therapy. It was therefore anticipated that the second group would have an MTD higher or at least as high as the first. Generally, likelihood methods or, equivalently, the use of noninformative Bayes priors, can be used to model the main aspects of the study, i.e., the MTD for one of the groups, reserving more informative Bayes modeling to be applied to the secondary features of the study. These secondary features may simply be the direction of the difference between the MTD levels for the two groups or, possibly, information on the potential gap between the two MTDs. [source]