A5058281659- Statistical Methods and Bayesian Inference
- Statistical Methods in Clinical Trials
- Advanced Causal Inference Techniques
- Health Systems, Economic Evaluations, Quality of Life
- Statistical Methods and Inference
- T-cell and B-cell Immunology
- Monoclonal and Polyclonal Antibodies Research
- Immunotherapy and Immune Responses
- Immune Cell Function and Interaction
- Optimal Experimental Design Methods
- Meta-analysis and systematic reviews
- Organ Transplantation Techniques and Outcomes
- Blood groups and transfusion
- Healthcare Technology and Patient Monitoring
- Antiplatelet Therapy and Cardiovascular Diseases
- Glycosylation and Glycoproteins Research
- Healthcare Operations and Scheduling Optimization
- Autoimmune Bullous Skin Diseases
- Renal Transplantation Outcomes and Treatments
- Advanced Statistical Process Monitoring
- HIV Research and Treatment
- Community Development and Social Impact
- Electromagnetic Launch and Propulsion Technology
- Autopsy Techniques and Outcomes
- Sarcoidosis and Beryllium Toxicity Research
London School of Hygiene & Tropical Medicine
2009-2024
Columbia University
2022
Newcastle University
2020
University of Kentucky
2019
University of London
2013-2015
GlaxoSmithKline (United Kingdom)
2005-2014
World Agroforestry Centre
1990
University of Reading
1976-1985
Biomedical Primate Research Centre
1976-1980
Long Island Jewish Medical Center
1979
Restricted maximum likelihood (REML) is now well established as a method for estimating the parameters of general Gaussian linear model with structured covariance matrix, in particular mixed models. Conventionally, estimates precision and inference fixed effects are based on their asymptotic distribution, which known to be inadequate some small-sample problems. In this paper, we present scaled Wald statistic, together an F approximation its sampling that shown perform range small sample...
SUMMARY.— The records of 554 consecutive patients attending hospitals in the Cambridge region with urticaria have been analysed aid a computer. These represent only small minority all region. In 79%, aetiology was unknown although many cases aggravating factors, for example, psychological stress, aspirin, or infection, were detected. A past family history atopic disorders not found more frequently than controls and course disease background atopy did differ from remainder, suggesting that an...
Protocol deviations, for example, due to early withdrawal and noncompliance, are unavoidable in clinical trials. Such deviations often result missing data. Additional assumptions then needed the analysis, these cannot be definitively verified from data at hand. Thus, as recognized by recent regulatory guidelines reports, clarity about their implications is vital both primary analysis framing relevant sensitivity analysis. This article focuses on trials with longitudinal quantitative outcome...
Journal Article A significance test for cyclic trends in incidence data Get access J. H. ROGER Department of Applied Statistics, University ReadingBerkshire Search other works by this author on: Oxford Academic Google Scholar Biometrika, Volume 64, Issue 1, April 1977, Pages 152–155, https://doi.org/10.1093/biomet/64.1.152 Published: 01 1977 history Received: July 1976 Revision received:
It is our experience that in many settings, crossover trials have within-period baseline measurements are analyzed wrongly. A "conventional" analysis of covariance this setting uses each as a covariate for the following outcome variable same period but not any other outcome. If used with random subject effects such an leads to biased treatment comparisons; example cross-level bias. Using postulated structure reflects symmetry setting, we quantify bias and, at time, investigate potential...
We introduce health technology assessment and evidence synthesis briefly, then concentrate on the statistical approaches used for conducting network meta-analysis (NMA) in development approval of new technologies. NMA is an extension standard where indirect as well direct information combined can be seen similar to analysis incomplete-block designs. illustrate it with example involving three treatments, using fixed-effects random-effects models, frequentist Bayesian approaches. As most...
Abstract Recent research has fostered new guidance on preventing and treating missing data. This article is the consensus opinion of Drug Information Association's Scientific Working Group Missing Data. Common elements from recent are distilled means for putting into action proposed. The primary goal to maximize proportion patients that adhere protocol specified interventions. In so doing, trial design conduct should be considered. Completion rate focused upon as much enrollment rate, with...
Abstract Statistical analyses of recurrent event data have typically been based on the missing at random assumption. One implication this is that, if are collected only when patients their randomized treatment, resulting de jure estimator treatment effect corresponds to situation in which adhere regime throughout study. For confirmatory analysis clinical trials, sensitivity required investigate alternative facto estimands that depart from Recent publications described use multiple imputation...
ICH E9 Statistical Principles for Clinical Trials was issued in 1998. In October 2014, an addendum to proposed relating estimands and sensitivity analyses. preparation the release of addendum, Statisticians Pharmaceutical Industry held a 1‐day expert group meeting February 2015. Topics debated included definition, development, implementation, education communication challenges associated with The topic is important relatively new one clinical development. A clear message from that bridge gap...
Journal Article HL‐A antigens in patients with guttate psoriasis Get access R.C. WILLIAMS, WILLIAMS Previously Department of Physical Anthropology, University Cambridge, Norfolk and Norwich Hospital, Applied Statistics, Reading, Tissue Typing Laboratory, Addenbrooke's Cambridge Search for other works by this author on: Oxford Academic Google Scholar A.W. McKENZIE, McKENZIE J.H. ROGER, ROGER V.C. JOYSEY British Dermatology, Volume 95, Issue 2, 1 August 1976, Pages 163–167,...
Adaptive designs (ADs) allow pre-planned changes to an ongoing trial without compromising the validity of conclusions and it is essential distinguish from unplanned that may also occur. The reporting ADs in randomised trials inconsistent needs improving. Incompletely reported AD are difficult reproduce hard interpret synthesise. This consequently hampers their ability inform practice as well future research contributes waste. Better transparency adequate will enable potential benefits be...
Five new serologically defined (SD) tissue antigens of rhesus monkeys are described. Results a population study and segregation analysis in families were consistent with their control by the major histocompatibility complex (MHC), as alleles two previously established SD loci RhL‐A. The number identifiable specificities monkeys'MHC is now twenty‐five, thirteen controlled 1 locus twelve 2 . recombination frequency between estimated to be 0.3%. No evidence third series, analogue human HLA—C...
The Points to Consider Document on Missing Data was adopted by the Committee of Health and Medicinal Products (CHMP) in December 2001. In September 2007 CHMP issued a recommendation review document, with particular emphasis summarizing critically appraising pattern drop-outs, explaining role limitations 'last observation carried forward' method describing CHMP's cautionary stance use mixed models. preparation for release updated guidance statisticians Pharmaceutical Industry held one-day...
Background We explored the theorized upregulation of platelet-activating factor (PAF)– mediated biologic responses following lipoprotein-associated phospholipase A2 (Lp-PLA2) inhibition using human platelet aggregation studies in an vitro experiment and 2 clinical trials. Methods Results Full concentration response curves were generated to several agonists plasma samples pretreated with rilapladib (selective Lp-PLA2 inhibitor) or vehicle. This was followed by a randomized, double-blind...
Network meta‐analysis can be implemented by using arm‐based or contrast‐based models. Here we focus on models and fit them generalized linear mixed model procedures. Full maximum likelihood (ML) estimation leads to biased trial‐by‐treatment interaction variance estimates for heterogeneity. Thus, our objective is investigate alternative approaches that reduce bias compared with full ML. Specifically, use penalized quasi‐likelihood/pseudo‐likelihood hierarchical (h) approaches. In addition,...
ABSTRACT The ICH E9(R1) Addendum (International Council for Harmonization 2019) suggests treatment‐policy as one of several strategies addressing intercurrent events such treatment withdrawal when defining an estimand. This strategy requires the monitoring patients and collection primary outcome data following termination randomised treatment. However, withdraw from a study early before completion this creates true missing complicating analysis. One possible way forward uses multiple...
Treatment effects on recurrent events are of primary clinical interest in many diseases such as asthma, multiple sclerosis or chronic heart failure. When death makes it impossible to experience further events, defining an appropriate measure the treatment effect, estimand, is challenging. For example failure, patients may repeated hospitalizations, but also at increased risk death. a test which reduces mortality compared control treatment, one observe more hospitalizations under simply...
In May 2012, the Committee of Health and Medicinal Products issued a concept paper on need to review points consider document multiplicity issues in clinical trials. preparation for release updated guidance document, Statisticians Pharmaceutical Industry held one‐day expert group meeting January 2013. Topics debated included drug development process, usefulness limitations newly developed strategies deal with multiplicity, arising from interim decisions multiregional development,...
Multivariate techniques of O'Brien's OLS and GLS statistics are discussed in the context their application clinical trials. We introduce concept an operational effect size illustrate its use to evaluate power. An extension describing how handle covariates missing data is developed Mixed models. This allowing adjustment for easily programmed any statistical package including SAS. Monte Carlo simulation used a number different sample sizes compare actual power tests based on statistics.