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Robertson SE, Steingrimsson JA, Dahabreh IJ. Cluster Randomized Trials Designed to Support Generalizable Inferences. EVALUATION REVIEW 2024:193841X231169557. [PMID: 38234059 DOI: 10.1177/0193841x231169557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
When planning a cluster randomized trial, evaluators often have access to an enumerated cohort representing the target population of clusters. Practicalities of conducting the trial, such as the need to oversample clusters with certain characteristics in order to improve trial economy or support inferences about subgroups of clusters, may preclude simple random sampling from the cohort into the trial, and thus interfere with the goal of producing generalizable inferences about the target population. We describe a nested trial design where the randomized clusters are embedded within a cohort of trial-eligible clusters from the target population and where clusters are selected for inclusion in the trial with known sampling probabilities that may depend on cluster characteristics (e.g., allowing clusters to be chosen to facilitate trial conduct or to examine hypotheses related to their characteristics). We develop and evaluate methods for analyzing data from this design to generalize causal inferences to the target population underlying the cohort. We present identification and estimation results for the expectation of the average potential outcome and for the average treatment effect, in the entire target population of clusters and in its non-randomized subset. In simulation studies, we show that all the estimators have low bias but markedly different precision. Cluster randomized trials where clusters are selected for inclusion with known sampling probabilities that depend on cluster characteristics, combined with efficient estimation methods, can precisely quantify treatment effects in the target population, while addressing objectives of trial conduct that require oversampling clusters on the basis of their characteristics.
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Affiliation(s)
- Sarah E Robertson
- CAUSALab, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Jon A Steingrimsson
- Department of Biostatistics, Brown University School of Public Health, Providence, RI, USA
| | - Issa J Dahabreh
- CAUSALab, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, MA, USA
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Nguyen TT, Lee SB, Kang JJ, Oh SY. Optimal Design of Galvanic Vestibular Stimulation for Patients with Vestibulopathy and Cerebellar Disorders. Brain Sci 2023; 13:1333. [PMID: 37759934 PMCID: PMC10526825 DOI: 10.3390/brainsci13091333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 09/02/2023] [Accepted: 09/15/2023] [Indexed: 09/29/2023] Open
Abstract
OBJECTIVES Galvanic vestibular stimulation (GVS) has shown positive outcomes in various neurological and psychiatric disorders, such as enhancing postural balance and cognitive functions. In order to expedite the practical application of GVS in clinical settings, our objective was to determine the best GVS parameters for patients with vestibulopathy and cerebellar disorders using optimal design calculation. METHODS A total of 31 patients (26 males, mean age 57.03 ± 14.75 years, age range 22-82 years) with either unilateral or bilateral vestibulopathy (n = 18) or cerebellar ataxia (n = 13) were enrolled in the study. The GVS intervention included three parameters, waveform (sinusoidal, direct current [DC], and noisy), amplitude (0.4, 0.8, and 1.2 mA), and duration of stimulation (5 and 30 min), resulting in a total of 18 GVS intervention modes as input variables. To evaluate the effectiveness of GVS, clinical vertigo and gait assessments were conducted using the Dizziness Visual Analogue Scale (D-VAS), Activities-specific Balance Confidence Scale (ABC), and Scale for Assessment and Rating of Ataxia (SARA) as output variables. Optimal design and local sensitivity analysis were employed to determine the most optimal GVS modes. RESULTS Patients with unilateral vestibulopathy experienced the most favorable results with either noisy or sinusoidal GVS at 0.4 mA amplitude for 30 min, followed by DC GVS at 0.8 mA amplitude for 5 min. Noisy GVS at 0.8 or 0.4 mA amplitude for 30 min demonstrated the most beneficial effects in patients with bilateral vestibulopathy. For patients with cerebellar ataxia, the optimal choices were noisy GVS with 0.8 or 0.4 mA amplitude for 5 or 30 min. CONCLUSIONS This study is the first to utilize design optimization methods to identify the GVS stimulation parameters that are tailored to individual-specific characteristics of dizziness and imbalance. A sensitivity analysis was carried out along with the optimal design to offset the constraints of a limited sample size, resulting in the identification of the most efficient GVS modes for patients suffering from vestibular and cerebellar disorders.
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Affiliation(s)
- Thanh Tin Nguyen
- Department of Neurology, Jeonbuk National University Hospital, Jeonbuk National University School of Medicine, Jeonju 54907, Republic of Korea; (T.T.N.); (J.-J.K.)
- Department of Pharmacology, Hue University of Medicine and Pharmacy, Hue University, Hue 49120, Vietnam
| | - Seung-Beop Lee
- School of International Engineering and Science, Graduate School of Integrated Energy-AI, Jeonbuk National University, Jeonju 54896, Republic of Korea;
| | - Jin-Ju Kang
- Department of Neurology, Jeonbuk National University Hospital, Jeonbuk National University School of Medicine, Jeonju 54907, Republic of Korea; (T.T.N.); (J.-J.K.)
- Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju 54907, Republic of Korea
| | - Sun-Young Oh
- Department of Neurology, Jeonbuk National University Hospital, Jeonbuk National University School of Medicine, Jeonju 54907, Republic of Korea; (T.T.N.); (J.-J.K.)
- Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju 54907, Republic of Korea
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Atkinson AC, Duarte BP, Pedrosa DJ, van Munster M. Randomizing a clinical trial in neuro-degenerative disease. Contemp Clin Trials Commun 2023; 33:101140. [PMID: 37180844 PMCID: PMC10172741 DOI: 10.1016/j.conctc.2023.101140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 03/26/2023] [Accepted: 04/12/2023] [Indexed: 05/16/2023] Open
Abstract
The paper studies randomization rules for a sequential two-treatment, two-site clinical trial in Parkinson's disease. An important feature is that we have values of responses and five potential prognostic factors from a sample of 144 patients similar to those to be enrolled in the trial. Analysis of this sample provides a model for trial analysis. The comparison of allocation rules is made by simulation yielding measures of loss due to imbalance and of potential bias. A major novelty of the paper is the use of this sample, via a two-stage algorithm, to provide an empirical distribution of covariates for the simulation; sampling of a correlated multivariate normal distribution is followed by transformation to variables following the empirical marginal distributions. Six allocation rules are evaluated. The paper concludes with some comments on general aspects of the evaluation of such rules and provides a recommendation for two allocation rules, one for each site, depending on the target number of patients to be enrolled.
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Affiliation(s)
- Anthony C. Atkinson
- Department of Statistics, London School of Economics, London WC2A 2AE, United Kingdom
- Corresponding author.
| | - Belmiro P.M. Duarte
- Polytechnic Institute of Coimbra, ISEC, Department of Chemical & Biological Engineering, Rua Pedro Nunes, 3030–199 Coimbra, Portugal
- Univ Coimbra, CIEPQPF, Department of Chemical Engineering, Rua Sílvio Lima — Pólo II, 3030–790 Coimbra, Portugal
| | - David J. Pedrosa
- Department of Neurology, University Hospital Marburg, 35043 Marburg, Germany
- Center of Brain, Mind and Behaviour, Philipps-University Marburg, 35043 Marburg, Germany
| | - Marlena van Munster
- Department of Neurology, University Hospital Marburg, 35043 Marburg, Germany
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Optimal designs for semi-parametric dose-response models under random contamination. Comput Stat Data Anal 2023. [DOI: 10.1016/j.csda.2022.107615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Berger VW, Bour LJ, Carter K, Chipman JJ, Everett CC, Heussen N, Hewitt C, Hilgers RD, Luo YA, Renteria J, Ryeznik Y, Sverdlov O, Uschner D. A roadmap to using randomization in clinical trials. BMC Med Res Methodol 2021; 21:168. [PMID: 34399696 PMCID: PMC8366748 DOI: 10.1186/s12874-021-01303-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 04/14/2021] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Randomization is the foundation of any clinical trial involving treatment comparison. It helps mitigate selection bias, promotes similarity of treatment groups with respect to important known and unknown confounders, and contributes to the validity of statistical tests. Various restricted randomization procedures with different probabilistic structures and different statistical properties are available. The goal of this paper is to present a systematic roadmap for the choice and application of a restricted randomization procedure in a clinical trial. METHODS We survey available restricted randomization procedures for sequential allocation of subjects in a randomized, comparative, parallel group clinical trial with equal (1:1) allocation. We explore statistical properties of these procedures, including balance/randomness tradeoff, type I error rate and power. We perform head-to-head comparisons of different procedures through simulation under various experimental scenarios, including cases when common model assumptions are violated. We also provide some real-life clinical trial examples to illustrate the thinking process for selecting a randomization procedure for implementation in practice. RESULTS Restricted randomization procedures targeting 1:1 allocation vary in the degree of balance/randomness they induce, and more importantly, they vary in terms of validity and efficiency of statistical inference when common model assumptions are violated (e.g. when outcomes are affected by a linear time trend; measurement error distribution is misspecified; or selection bias is introduced in the experiment). Some procedures are more robust than others. Covariate-adjusted analysis may be essential to ensure validity of the results. Special considerations are required when selecting a randomization procedure for a clinical trial with very small sample size. CONCLUSIONS The choice of randomization design, data analytic technique (parametric or nonparametric), and analysis strategy (randomization-based or population model-based) are all very important considerations. Randomization-based tests are robust and valid alternatives to likelihood-based tests and should be considered more frequently by clinical investigators.
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Affiliation(s)
| | | | - Kerstine Carter
- Boehringer-Ingelheim Pharmaceuticals Inc, Ridgefield, CT USA
| | - Jonathan J. Chipman
- Population Health Sciences, University of Utah School of Medicine, Salt Lake City UT, USA
- Cancer Biostatistics, University of Utah Huntsman Cancer Institute, Salt Lake City UT, USA
| | | | - Nicole Heussen
- RWTH Aachen University, Aachen, Germany
- Medical School, Sigmund Freud University, Vienna, Austria
| | - Catherine Hewitt
- York Trials Unit, Department of Health Sciences, University of York, York, UK
| | | | | | - Jone Renteria
- Open University of Catalonia (UOC) and the University of Barcelona (UB), Barcelona, Spain
- Department of Human Development and Quantitative Methodology, University of Maryland, College Park, MD USA
| | - Yevgen Ryeznik
- BioPharma Early Biometrics & Statistical Innovations, Data Science & AI, R&D BioPharmaceuticals, AstraZeneca, Gothenburg, Sweden
| | - Oleksandr Sverdlov
- Early Development Analytics, Novartis Pharmaceuticals Corporation, NJ East Hanover, USA
| | - Diane Uschner
- Biostatistics Center & Department of Biostatistics and Bioinformatics, George Washington University, DC Washington, USA
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Ryeznik Y, Sverdlov O, Svensson EM, Montepiedra G, Hooker AC, Wong WK. Pharmacometrics meets statistics-A synergy for modern drug development. CPT-PHARMACOMETRICS & SYSTEMS PHARMACOLOGY 2021; 10:1134-1149. [PMID: 34318621 PMCID: PMC8520751 DOI: 10.1002/psp4.12696] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 05/17/2021] [Accepted: 07/02/2021] [Indexed: 01/20/2023]
Abstract
Modern drug development problems are very complex and require integration of various scientific fields. Traditionally, statistical methods have been the primary tool for design and analysis of clinical trials. Increasingly, pharmacometric approaches using physiology-based drug and disease models are applied in this context. In this paper, we show that statistics and pharmacometrics have more in common than what keeps them apart, and collectively, the synergy from these two quantitative disciplines can provide greater advances in clinical research and development, resulting in novel and more effective medicines to patients with medical need.
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Affiliation(s)
- Yevgen Ryeznik
- BioPharma Early Biometrics and Statistical Innovation, Data Science & AI, R&D Biopharmaceuticals, AstraZeneca, Gothenburg, Sweden
| | - Oleksandr Sverdlov
- Early Development Analytics, Novartis Pharmaceuticals Corporation, East Hanover, New Jersey, USA
| | - Elin M Svensson
- Department of Pharmacy, Uppsala University, Uppsala, Sweden.,Department of Pharmacy, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Grace Montepiedra
- Center for Biostatistics in AIDS Research, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | | | - Weng Kee Wong
- Department of Biostatistics, University of California Los Angeles, Los Angeles, California, USA
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Tsirpitzi RE, Miller F. Optimal dose-finding for efficacy-safety models. Biom J 2021; 63:1185-1201. [PMID: 33829555 DOI: 10.1002/bimj.202000181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 12/11/2020] [Accepted: 01/22/2021] [Indexed: 11/05/2022]
Abstract
Dose-finding is an important part of the clinical development of a new drug. The purpose of dose-finding studies is to determine a suitable dose for future development based on both efficacy and safety. Optimal experimental designs have already been used to determine the design of this kind of studies, however, often that design is focused on efficacy only. We consider an efficacy-safety model, which is a simplified version of the bivariate Emax model. We use here the clinical utility index concept, which provides the desirable balance between efficacy and safety. By maximizing the utility of the patients, we get the estimated dose. This desire leads us to locally c -optimal designs. An algebraic solution for c -optimal designs is determined for arbitrary c vectors using a multivariate version of Elfving's method. The solution shows that the expected therapeutic index of the drug is a key quantity determining both the number of doses, the doses itself, and their weights in the optimal design. A sequential design is proposed to solve the complication of parameter dependency, and it is illustrated in a simulation study.
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Affiliation(s)
| | - Frank Miller
- Department of Statistics, Stockholm University, Stockholm, Sweden
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