Effects of unstratified and centre-stratified randomization in multi-centre clinical trials

Prednisolone Versus Colchicine for Acute Gout in Primary Care: statistical analysis plan for the pragmatic, multicenter, randomized, and double-blinded COPAGO non-inferiority trial

BACKGROUND

To date, colchicine and prednisolone are two effective therapies for the treatment of acute gout but have never been compared directly in a randomized clinical trial. In addition, in previous trials of treating acute gout patients with concomitant comorbidities were often excluded due to contraindications to naproxen.

STUDY DESIGN

This pragmatic, prospective, double-blind, double-dummy, parallel-group, randomized, non-inferiority trial compares prednisolone with colchicine in terms of non-inferiority in patients with acute gout. Patients presenting to their general practitioner with acute gout can be included if the gout attack has occurred within the last 2 days. A total of 60 practices in the vicinity of three university medical centers (Greifswald, Göttingen, and Würzburg) participate in the study. The intervention group receives 30 mg prednisolone for 5 days, while the group of standard care receives low-dose colchicine (day 1: 1.5 mg; days 2-5: 1 mg). The first dose of treatment is provided at day 0 when patients present to the general practitioner due to an acute gout attack. From day 0 to day 6, patients will be asked to complete a study diary on daily basis regarding pain quantification. For safety reasons, potential side effects and the course of systolic blood pressure are also assessed.

STATISTICAL ANALYSIS PLAN

N = 314 patients have to be recruited to compensate for 10% of dropout and to allow for showing non-inferiority of prednisolone compared to colchicine with a power of 90%. We use permuted block randomization with block sizes of 2, 4, and 6 to avoid imbalanced treatment arms in this multi-center study; patients are randomized in a 1:1 ratio. The absolute level of pain on day 3 (in the last 24 h) is the primary outcome and measured on a numerical rating scale (NRS: 0-10). Using a multiple linear regression model adjusted for age, sex, and pain at baseline, prednisolone is considered non-inferior if the effect estimate including the confidence intervals is lower than a margin of 1 unit on the NRS. Average response to treatment, joint swelling and tenderness, physical function of the joint, and patients' global assessment of treatment success are secondary outcomes.

DISCUSSION

The trial will provide evidence from a direct comparison of colchicine and prednisolone regarding their efficacy of pain reduction in acute gout patients of primary care and to indicate possible safety signals.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05698680 first posted on January 26, 2023 (retrospectively registered).

Selecting a randomization method for a multi-center clinical trial with stochastic recruitment considerations

BACKGROUND

The design of a multi-center randomized controlled trial (RCT) involves multiple considerations, such as the choice of the sample size, the number of centers and their geographic location, the strategy for recruitment of study participants, amongst others. There are plenty of methods to sequentially randomize patients in a multi-center RCT, with or without considering stratification factors. The goal of this paper is to perform a systematic assessment of such randomization methods for a multi-center 1:1 RCT assuming a competitive policy for the patient recruitment process.

METHODS

We considered a Poisson-gamma model for the patient recruitment process with a uniform distribution of center activation times. We investigated 16 randomization methods (4 unstratified, 4 region-stratified, 4 center-stratified, 3 dynamic balancing randomization (DBR), and a complete randomization design) to sequentially randomize n = 500 patients. Statistical properties of the recruitment process and the randomization procedures were assessed using Monte Carlo simulations. The operating characteristics included time to complete recruitment, number of centers that recruited a given number of patients, several measures of treatment imbalance and estimation efficiency under a linear model for the response, the expected proportions of correct guesses under two different guessing strategies, and the expected proportion of deterministic assignments in the allocation sequence.

RESULTS

Maximum tolerated imbalance (MTI) randomization methods such as big stick design, Ehrenfest urn design, and block urn design result in a better balance-randomness tradeoff than the conventional permuted block design (PBD) with or without stratification. Unstratified randomization, region-stratified randomization, and center-stratified randomization provide control of imbalance at a chosen level (trial, region, or center) but may fail to achieve balance at the other two levels. By contrast, DBR does a very good job controlling imbalance at all 3 levels while maintaining the randomized nature of treatment allocation. Adding more centers into the study helps accelerate the recruitment process but at the expense of increasing the number of centers that recruit very few (or no) patients-which may increase center-level imbalances for center-stratified and DBR procedures. Increasing the block size or the MTI threshold(s) may help obtain designs with improved randomness-balance tradeoff.

CONCLUSIONS

The choice of a randomization method is an important component of planning a multi-center RCT. Dynamic balancing randomization with carefully chosen MTI thresholds could be a very good strategy for trials with the competitive policy for patient recruitment.

Preanalytical Pitfalls in Untargeted Plasma Nuclear Magnetic Resonance Metabolomics of Endocrine Hypertension

Despite considerable morbidity and mortality, numerous cases of endocrine hypertension (EHT) forms, including primary aldosteronism (PA), pheochromocytoma and functional paraganglioma (PPGL), and Cushing’s syndrome (CS), remain undetected. We aimed to establish signatures for the different forms of EHT, investigate potentially confounding effects and establish unbiased disease biomarkers. Plasma samples were obtained from 13 biobanks across seven countries and analyzed using untargeted NMR metabolomics. We compared unstratified samples of 106 PHT patients to 231 EHT patients, including 104 PA, 94 PPGL and 33 CS patients. Spectra were subjected to a multivariate statistical comparison of PHT to EHT forms and the associated signatures were obtained. Three approaches were applied to investigate and correct confounding effects. Though we found signatures that could separate PHT from EHT forms, there were also key similarities with the signatures of sample center of origin and sample age. The study design restricted the applicability of the corrections employed. With the samples that were available, no biomarkers for PHT vs. EHT could be identified. The complexity of the confounding effects, evidenced by their robustness to correction approaches, highlighted the need for a consensus on how to deal with variabilities probably attributed to preanalytical factors in retrospective, multicenter metabolomics studies.

Smoking cessation using preference-based tools among socially disadvantaged smokers: study protocol for a pragmatic, multicentre randomised controlled trial

INTRODUCTION

Many smoking cessation aids such as nicotine replacement treatments and e-cigarettes have been proven effective in aiding smoking cessation attempts. Encouraging smokers with low socioeconomic position (SEP) to choose their smoking aid tool based on their preferences, and giving that tool free of charge, might increase the odds of smoking cessation. This trial examines the effectiveness of the 'STOP' (Sevrage Tabagique à l'aide d'Outils dédiés selon la Préférence: Smoking cessation using preference-based tools), a preference-based smoking cessation intervention for smokers with low SEP.

METHODS AND ANALYSIS

The STOP study is a randomised, multicentre, controlled trial (RCT). Smokers with low SEP and wishing to quit will be randomised to either the intervention or the control group (standard care). Participants in the intervention group will be asked to choose between different types of nicotine substitutes (patches, inhalers, gum, tablets, etc) and/or an electronic cigarette which will be delivered free of charge to aid their smoking cessation attempt.The primary outcome will be smoking abstinence at 6 months after inclusion, defined as self-reported 7-day point prevalence of tobacco abstinence. Secondary outcomes include the total number of days of abstinence at 6 months after inclusion, 7-day point prevalence tobacco abstinence at 1 and 3 months after inclusion and number of relapses.The study will also include an economic evaluation, and a process evaluation using a mixed methods approach.

ETHICS AND DISSEMINATION

The study was approved by the 'Île de France II' Institutional Review Board on 8 September 2020 (CPP Île de France II; Ref No: 20.01.31.65528 RIPH2 HPS), and results will be published in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT04654585.

Concomitant food intake does not affect the efficacy of entecavir in chronic hepatitis B patients with virological response: a randomized, multicenter, noninferiority trial

Background

Little clinical data are available about the effect of food on the antiviral efficacy of entecavir for chronic hepatitis B virus (HBV) infection. The present study evaluated whether entecavir administration in the fed state had comparable efficacy to the fasted condition for maintenance of viral suppression in HBV-infected patients with virological response on entecavir therapy.

Methods

In this multicenter, randomized, open-label, noninferiority study, patients who were currently receiving entecavir and showed a serum HBV DNA level of <20 IU/mL were randomized to take entecavir either under the fasted or fed condition for 48 weeks.

Results

We randomly assigned 50 patients to the fasted group and 46 patients to the fed group. The full analysis set consisted of 49 patients in the fasted group and 44 patients in the fed group. At week 48, the proportion of patients with HBV DNA <20 IU/mL was not significantly different between the fasted and fed groups (98% vs 100%, P=1.00). The mean log₁₀ HBV DNA changes from baseline were similar between the two groups (−0.004 vs −0.012 log₁₀ IU/mL, P=0.43). There were no significant differences in the proportions of patients with normal alanine aminotransferase (87.8% vs 95.5%, P=0.27) and hepatitis B e-antigen seroconversion (0% vs 6.7%, P=0.47) between the two groups. None of the patients showed viral breakthrough. In pharmacokinetic analysis, the maximum concentration and the area under the concentration– time curve to the last quantifiable concentration decreased by 26.4% and 9.3%, respectively, in the fed group compared with the fasted group. However, the differences between two groups were not statistically significant (P=0.28 and 0.83, respectively).

Conclusion

In patients with virological response under entecavir therapy, concomitant food intake did not affect the antiviral efficacy. For patients with adherence problem, taking entecavir with food may be considered to improve compliance.

Imbalance properties of centre-stratified permuted-block and complete randomisation for several treatments in a clinical trial

Randomisation schemes are rules that assign patients to treatments in a clinical trial. Many of these schemes have the common aim of maintaining balance in the numbers of patients across treatment groups. The properties of imbalance that have been investigated in the literature are based on two treatment groups. In this paper, their properties for K > 2 treatments are studied for two randomisation schemes: centre-stratified permuted-block and complete randomisation. For both randomisation schemes, analytical approaches are investigated assuming that the patient recruitment process follows a Poisson-gamma model. When the number of centres involved in a trial is large, the imbalance for both schemes is approximated by a multivariate normal distribution. The accuracy of the approximations is assessed by simulation. A test for treatment differences is also considered for normal responses, and numerical values for its power are presented for centre-stratified permuted-block randomisation. To speed up the calculations, a combined analytical/approximate approach is used. Copyright © 2016 John Wiley & Sons, Ltd.

How to deal with the Poisson-gamma model to forecast patients' recruitment in clinical trials when there are pauses in recruitment dynamic?

Recruiting patients is a crucial step of a clinical trial. Estimation of the trial duration is a question of paramount interest. Most techniques are based on deterministic models and various ad hoc methods neglecting the variability in the recruitment process. To overpass this difficulty the so-called Poisson-gamma model has been introduced involving, for each centre, a recruitment process modelled by a Poisson process whose rate is assumed constant in time and gamma-distributed. The relevancy of this model has been widely investigated. In practice, rates are rarely constant in time, there are breaks in recruitment (for instance week-ends or holidays). Such information can be collected and included in a model considering piecewise constant rate functions yielding to an inhomogeneous Cox model. The estimation of the trial duration is much more difficult. Three strategies of computation of the expected trial duration are proposed considering all the breaks, considering only large breaks and without considering breaks. The bias of these estimations procedure are assessed by means of simulation studies considering three scenarios of breaks simulation. These strategies yield to estimations with a very small bias. Moreover, the strategy with the best performances in terms of prediction and with the smallest bias is the one which does not take into account of breaks. This result is important as, in practice, collecting breaks data is pretty hard to manage.

Building efficient comparative effectiveness trials through adaptive designs, utility functions, and accrual rate optimization: finding the sweet spot

The time is right for the use of Bayesian Adaptive Designs (BAD) in comparative effectiveness trials. For example, Patient Centered Outcomes Research Institute has joined the Food and Drug Administration and National Intitutes of Health in adopting policies/guidelines encouraging their use. There are multiple aspects to BAD that need to be considered when designing a comparative effectiveness design. First, the adaptation rules can determine the expected size of the trial. Second, a utility function can be used to combine extremely important co-endpoints (e.g., efficacy and tolerability) and is a valuable tool for incorporating clinical expertise and potentially patient preference. Third, accrual rate is also very, very important. Specifically, there is a juxtaposition related to accrual and BAD. If accrual rate is too fast we never gain efficient information for adapting. If accrual rate is too slow we never finish the clinical trial. We propose methodology for finding the 'sweet spot' for BAD that addresses these as design parameters. We demonstrate the methodology on a comparative effectiveness BAD of pharmaceutical agents in cryptogenic sensory polyneuropathy. The study has five arms with two endpoints that are combined with a utility function. The accrual rate is assumed to stem from multiple sites. We perform simulations from which the composite accrual rates across sites result in various piecewise Poisson distributions as parameter inputs. We balance both average number of patients needed and average length of time to finish the study.

The effect of nocturnal wear of complete dentures on sleep and oral health related quality of life: study protocol for a randomized controlled trial

BACKGROUND

Edentulism and sleep disturbance are chronic conditions that are common in older people and have serious adverse consequences for their functioning and quality of life. Edentulism can disturb sleep through the alteration of the craniofacial structure and surrounding soft tissue. However, the effect of prosthetic rehabilitation of edentulism on sleep quality is still not well understood. The objectives of this study are to test whether nocturnal denture wear affects sleep quality, daytime sleepiness, and the oral health related quality of life of edentate older people with moderate to severe sleep apnea, and to identify modifiers of effect of nocturnal denture wear.

METHODS/DESIGN

We will carry out a single-blind randomized cross-over trial. Seventy edentate older people with moderate to severe obstructive sleep apnea will be enrolled. The study participants will be assigned to wear and not wear their dentures on alternate periods of 30 days. The outcome measures will be sleep quality (assessed by portable polysomnography), daytime sleepiness (assessed by the Epworth Sleepiness Scale), and oral health related quality of life (assessed by validated questionnaire). A number of characteristics (sociodemographic, oropharyngeal morphology, oral and prosthesis characteristics, and perceived general health quality of life) will be assessed by means of clinical examination, 3D imaging of the craniofacial structure, and validated questionnaires at baseline. Linear mixed effects regression models for repeated measures will be fitted to test the study hypotheses. The main analyses will be based on the intention-to-treat principle. To assess the robustness of the findings to potential incomplete adherence, sensitivity analyses will be conducted while applying the per-protocol principle.

DISCUSSION

This practice-relevant evidence could represent a preventive approach to improve sleep characteristics of the older population and improve their well-being and quality of life.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01868295.