Clinical trials with mechanism evaluation of intervention(s): mind the power and sample size calculation.

BACKGROUND: Mediation analysis, often completed as secondary analysis to estimating the main treatment effect, investigates situations where an exposure may affect an outcome both directly and indirectly through intervening mediator variables. Although there has been much research on power in mediation analyses, most of this has focused on the power to detect indirect effects. Little consideration has been given to the extent to which the strength of the mediation pathways, i.e., the intervention-mediator path and the mediator-outcome path respectively, may affect the power to detect the total effect, which would correspond to the intention-to-treat effect in a randomized trial. METHODS: We conduct a simulation study to evaluate the relation between the mediation pathways and the power of testing the total treatment effect, i.e., the intention-to-treat effect. Consider a sample size that is computed based on the usual formula for testing the total effect in a two-arm trial. We generate data for a continuous mediator and a normal outcome using the conventional mediation models. We estimate the total effect using simple linear regression and evaluate the power of a two-sided test. We explore multiple data generating scenarios by varying the magnitude of the mediation paths whilst keeping the total effect constant. RESULTS: Simulations show the estimated total effect is unbiased across the considered scenarios as expected, but the mean of its standard error increases with the magnitude of the mediator-outcome path and the variability in the residual error of the mediator, respectively. Consequently, this affects the power of testing the total effect, which is always lower than planned when the mediator-outcome path is non-trivial and a naive sample size was employed. Analytical explanation confirms that the intervention-mediator path does not affect the power of testing the total effect but the mediator-outcome path. The usual effect size consideration can be adjusted to account for the magnitude of the mediator-outcome path and its residual error. CONCLUSIONS: The sample size calculation for studies with efficacy and mechanism evaluation should account for the mediator-outcome association or risk the power to detect the total effect/intention-to-treat effect being lower than planned.

Study protocol for an adaptive, multi-arm, multi-stage (MAMS) randomised controlled trial of brief remotely delivered psychosocial interventions for people with serious mental health problems who have experienced a recent suicidal crisis: Remote Approaches to Psychosocial Intervention Delivery (RAPID).

BACKGROUND: People with serious mental health problems (SMHP) are more likely to be admitted to psychiatric hospital following contact with crisis services. Admissions can have significant personal costs, be traumatic and are the most expensive form of mental health care. There is an urgent need for treatments to reduce suicidal thoughts and behaviours and reduce avoidable psychiatric admissions. METHODS: A multi-stage, multi-arm (MAMS) randomised controlled trial (RCT) with four arms conducted over two stages to determine the clinical and cost effectiveness of three psychosocial treatments, compared to treatment as usual (TAU), for people with SMHP who have had recent suicidal crisis. Primary outcome is any psychiatric hospital admissions over a 6-month period. We will assess the impact on suicidal thoughts and behaviour, hope, recovery, anxiety and depression. The remote treatments delivered over 3 months are structured peer support (PREVAIL); a safety planning approach (SAFETEL) delivered by assistant psychologists; and a CBT-based suicide prevention app accessed via a smartphone (BrighterSide). Recruitment is at five UK sites. Stage 1 includes an internal pilot with a priori progression criteria. In stage 1, the randomisation ratio was 1:1:1:2 in favour of TAU. This has been amended to 2:2:3 in favour of TAU following an unplanned change to remove the BrighterSide arm following the release of efficacy data from an independent RCT. Randomisation is via an independent remote web-based randomisation system using randomly permuted blocks, stratified by site. An interim analysis will be performed using data from the first 385 participants from PREVAIL, SAFETEL and TAU with outcome data at 6 months. If one arm is dropped for lack of benefit in stage 2, the allocation ratio of future participants will be 1:1. The expected total sample size is 1064 participants (1118 inclusive of BrighterSide participants). DISCUSSION: There is a need for evidence-based interventions to reduce psychiatric admissions, via reduction of suicidality. Our focus on remote delivery of established brief psychosocial interventions, utilisation of different modalities of delivery that can provide sustainable and scalable solutions, which are also suitable for a pandemic or national crisis context, will significantly advance treatment options. TRIAL REGISTRATION: ISRCTN33079589. Registered on June 20, 2022.

The impact of heterogeneity on the analysis of platform trials with normally distributed outcomes.

BACKGROUND: A platform trial approach allows adding arms to on-going trials to speed up intervention discovery programs. A control arm remains open for recruitment in a platform trial while intervention arms may be added after the onset of the study and could be terminated early for efficacy and/or futility when early stopping is allowed. The topic of utilising non-concurrent control data in the analysis of platform trials has been explored and discussed extensively. A less familiar issue is the presence of heterogeneity, which may exist for example due to modification of enrolment criteria and recruitment strategy. METHOD: We conduct a simulation study to explore the impact of heterogeneity on the analysis of a two-stage platform trial design. We consider heterogeneity in treatment effects and heteroscedasticity in outcome data across stages for a normally distributed endpoint. We examine the performance of some hypothesis testing procedures and modelling strategies. The use of non-concurrent control data is also considered accordingly. Alongside standard regression analysis, we examine the performance of a novel method that was known as the pairwise trials analysis. It is similar to a network meta-analysis approach but adjusts for treatment comparisons instead of individual studies using fixed effects. RESULTS: Several testing strategies with concurrent control data seem to control the type I error rate at the required level when there is heteroscedasticity in outcome data across stages and/or a random cohort effect. The main parameter of treatment effects in some analysis models correspond to overall treatment effects weighted by stage wise sample sizes; while others correspond to the effect observed within a single stage. The characteristics of the estimates are not affected significantly by the presence of a random cohort effect and/ or heteroscedasticity. CONCLUSION: In view of heterogeneity in treatment effect across stages, the specification of null hypotheses in platform trials may need to be more subtle. We suggest employing testing procedure of adaptive design as opposed to testing the statistics from regression models; comparing the estimates from the pairwise trials analysis method and the regression model with interaction terms may indicate if heterogeneity is negligible.

The role of accelerometer-derived sleep traits on glycated haemoglobin and glucose levels: a Mendelian randomization study.

Self-reported shorter/longer sleep duration, insomnia, and evening preference are associated with hyperglycaemia in observational analyses, with similar observations in small studies using accelerometer-derived sleep traits. Mendelian randomization (MR) studies support an effect of self-reported insomnia, but not others, on glycated haemoglobin (HbA1c). To explore potential effects, we used MR methods to assess effects of accelerometer-derived sleep traits (duration, mid-point least active 5-h, mid-point most active 10-h, sleep fragmentation, and efficiency) on HbA1c/glucose in European adults from the UK Biobank (UKB) (n = 73,797) and the MAGIC consortium (n = 146,806). Cross-trait linkage disequilibrium score regression was applied to determine genetic correlations across accelerometer-derived, self-reported sleep traits, and HbA1c/glucose. We found no causal effect of any accelerometer-derived sleep trait on HbA1c or glucose. Similar MR results for self-reported sleep traits in the UKB sub-sample with accelerometer-derived measures suggested our results were not explained by selection bias. Phenotypic and genetic correlation analyses suggested complex relationships between self-reported and accelerometer-derived traits indicating that they may reflect different types of exposure. These findings suggested accelerometer-derived sleep traits do not affect HbA1c. Accelerometer-derived measures of sleep duration and quality might not simply be 'objective' measures of self-reported sleep duration and insomnia, but rather captured different sleep characteristics.

Effects of Actissist, a digital health intervention for early psychosis: A randomized clinical trial.

Schizophrenia affects 24 million people worldwide. Digital health interventions drawing on psychological principles have been developed, but their effectiveness remains unclear. This parallel, assessor-blinded, randomized clinical trial aimed to investigate whether a cognitive behaviour therapy-informed digital health intervention (Actissist app) confers added benefit on psychotic symptoms over and above remote symptom monitoring (ClinTouch app). Participants recruited from UK community health services were randomized 1:1 to receive either Actissist plus treatment as usual (TAU) or ClinTouch plus TAU. Eligible participants were adults with schizophrenia-spectrum psychosis within five years of first episode onset meeting a criterion level of positive symptoms severity. The primary outcome was Positive and Negative Syndrome Scale (PANSS) symptoms total score at 12 weeks post-randomization. Intention-to-treat analysis included 172 participants, with 149 participants (86.6 %) providing primary outcome data. Actissist plus TAU was not associated with greater reduction than an active control remote symptom monitoring app (ClinTouch) in PANSS total score at post-randomization. There were no significant effects between groups across secondary measures. There were no serious adverse reactions. Both groups improved on the primary psychotic symptoms measure at primary end-point and on secondary measures over time. The Actissist app is safe but not superior to digital symptom monitoring.

The CATFISH study: An evaluation of a water fluoridation program in Cumbria, UK.

OBJECTIVES: The objective was to assess the effectiveness of a Water Fluoridation program on a contemporary population of children. METHODS: The study used a longitudinal prospective cohort design. In Cumbria, England, two groups of children were recruited and observed over a period of 5-6 years. The Birth Cohort consisted of families recruited from two hospitals in Cumbria where children were conceived after water fluoridation was reintroduced. The systemic and topical effects of community water fluoridation were evaluated in the Birth Cohort. The Older Cohort were approximately 5 years old and recruited from primary schools in Cumbria, shortly after water fluoridation was reintroduced. The predominantly topical effects of fluoridated water were evaluated in the Older Cohort. The primary outcome was the proportion of children with clinical evidence of caries experience in their primary (Birth Cohort) or permanent teeth (Older Cohort). Unadjusted and adjusted regression models were used for analysis. RESULTS: The final clinical examinations for the Birth Cohort involved 1444 participants (mean age 4.8 years), where 17.4% of children in the intervention group were found to have caries experience, compared to 21.4% in the control group. A beneficial effect of water fluoridation was observed adjusting for deprivation (a socioeconomic measure), sex, and age, (adjusted odds ratio 0.74 95% CI 0.55 to 0.98). The final Older Cohort clinical examinations involved 1192 participants (mean age 10.8 years) where 19.1% of children in the intervention group were found to have caries experience compared to 21.9% in the control group (adjusted odds ratio 0.80, 95% CI 0.58 to 1.09). For both the Birth Cohort and Older Cohort there was evidence of a beneficial effect on dmft/DMFT count (IRR 0.61, 95% CI 0.44, 0.86) and (IRR 0.69, 95% CI 0.52, 0.93) respectively. No conclusive proof was found to indicate that the effectiveness of water fluoridation differed across area deprivation quintiles. CONCLUSIONS: In the contemporary context of lower caries levels and widespread use of fluoride toothpaste, the impact of water fluoridation on the prevalence of caries was smaller than previous studies have reported. It is important to consider the clinical importance of the absolute reduction in caries prevalence against the use of other dental caries preventive measures.

Generalisation of Social Communication Skills by Autistic Children During Play-Based Assessments Across Home, School and an Unfamiliar Research Setting.

We investigated autistic children's generalisation of social communication over time across three settings during a play-based assessment with different adults and explore the potential moderating effects on generalisation of age, nonverbal IQ and level of restricted and repetitive behaviours. The social communication abilities of 248 autistic children (2-11 years, 21% female, 22% single parent, 60% white) from three UK sites were assessed from 1984 video interactions in three contexts with three different interaction partners (parent/home, teaching assistant/school, researcher/clinic) at baseline, midpoint (+ 7m) and endpoint (+ 12m) within the Paediatric Autism Communication Trial-Generalised (PACT-G), a parent-mediated social communication intervention. Children's midpoint social communication at home generalised to school at midpoint and to clinic at endpoint. Generalisation was stronger from home to school and clinic than school to home and clinic. Generalisation was not moderated by age, nonverbal IQ or restricted and repetitive behaviour. Broader child development did not explain the pattern of results. The current study is the largest study to date to explore generalisation with autistic children and provides novel insight into their generalisation of social communication skills. Further research is needed to gain a more comprehensive understanding of facilitators of generalisation across settings and interaction partners in order to develop targeted strategies for interventions to enhance outcomes for young autistic children.

Economic evaluation of a water fluoridation scheme in Cumbria, UK.

OBJECTIVES: The addition of fluoride to community drinking water supplies has been a long-standing public health intervention to improve dental health. However, the evidence of cost-effectiveness in the UK currently lacks a contemporary focus, being limited to a period with higher incidence of caries. A water fluoridation scheme in West Cumbria, United Kingdom, provided a unique opportunity to study the contemporary impact of water fluoridation. This study evaluates the cost-effectiveness of water fluoridation over a 5-6 years follow-up period in two distinct cohorts: children exposed to water fluoridation in utero and those exposed from the age of 5. METHODS: Cost-effectiveness was summarized employing incremental cost-effectiveness ratios (ICER, cost per quality adjusted life year (QALY) gained). Costs included those from the National Health Service (NHS) and local authority perspective, encompassing capital and running costs of water fluoridation, as well as NHS dental activity. The measure of health benefit was the QALY, with utility determined using the Child Health Utility 9-Dimension questionnaire. To account for uncertainty, estimates of net cost and outcomes were bootstrapped (10 000 bootstraps) to generate cost-effectiveness acceptability curves and sensitivity analysis performed with alternative specifications. RESULTS: There were 306 participants in the birth cohort (189 and 117 in the non-fluoridated and fluoridated groups, respectively) and 271 in the older school cohort (159 and 112, respectively). In both cohorts, there was evidence of small gains in QALYs for the fluoridated group compared to the non-fluoridated group and reductions in NHS dental service cost that exceeded the cost of fluoridation. For both cohorts and across all sensitivity analyses, there were high probabilities (>62%) of water fluoridation being cost-effective with a willingness to pay threshold of £20 000 per QALY. CONCLUSIONS: This analysis provides current economic evidence that water fluoridation is likely to be cost-effective. The findings contribute valuable contemporary evidence in support of the economic viability of water fluoridation scheme.

Safety and efficacy of autologous haematopoietic stem-cell transplantation with low-dose cyclophosphamide mobilisation and reduced intensity conditioning versus standard of care in refractory Crohn's disease (ASTIClite): an open-label, multicentre, randomised controlled trial.

BACKGROUND: A previous controlled trial of autologous haematopoietic stem-cell transplantation (HSCT) in patients with refractory Crohn's disease did not meet its primary endpoint and reported high toxicity. We aimed to assess the safety and efficacy of HSCT with an immune-ablative regimen of reduced intensity versus standard of care in this patient population. METHODS: This open-label, multicentre, randomised controlled trial was conducted in nine National Health Service hospital trusts across the UK. Adults (aged 18-60 years) with active Crohn's disease on endoscopy (Simplified Endoscopic Score for Crohn's Disease [SES-CD] ulcer sub-score of ≥2) refractory to two or more classes of biological therapy, with no perianal or intra-abdominal sepsis or clinically significant comorbidity, were recruited. Participants were centrally randomly assigned (2:1) to either HSCT with a reduced dose of cyclophosphamide (intervention group) or standard care (control group). Randomisation was stratified by trial site by use of random permuted blocks of size 3 and 6. Patients in the intervention group underwent stem-cell mobilisation (cyclophosphamide 1 g/m2 with granulocyte colony-stimulating factor (G-CSF) 5 µg/kg) and stem-cell harvest (minimum 2·0 × 106 CD34+ cells per kg), before conditioning (fludarabine 125 mg/m2, cyclophosphamide 120 mg/kg, and rabbit anti-thymocyte globulin [thymoglobulin] 7·5 mg/kg in total) and subsequent stem-cell reinfusion supported by G-CSF. Patients in the control group continued any available conventional, biological, or nutritional therapy. The primary outcome was absence of endoscopic ulceration (SES-CD ulcer sub-score of 0) without surgery or death at week 48, analysed in the intention-to-treat population by central reading. This trial is registered with the ISRCTN registry, 17160440. FINDINGS: Between Oct 18, 2018, and Nov 8, 2019, 49 patients were screened for eligibility, of whom 23 (47%) were randomly assigned: 13 (57%) to the intervention group and ten (43%) to the control group. In the intervention group, ten (77%) participants underwent HSCT and nine (69%) reached 48-week follow-up; in the control group, nine (90%) reached 48-week follow-up. The trial was halted in response to nine reported suspected unexpected serious adverse reactions in six (46%) patients in the intervention group, including renal failure due to proven thrombotic microangiopathy in three participants and one death due to pulmonary veno-occlusive disease. At week 48, absence of endoscopic ulceration without surgery or death was reported in three (43%) of seven participants in the intervention group and in none of six participants in the control group with available data. Serious adverse events were more frequent in the intervention group (38 in 13 [100%] patients) than in the control group (16 in four [40%] patients). A second patient in the intervention group died after week 48 of respiratory and renal failure. INTERPRETATION: Although HSCT with an immune-ablative regimen of reduced intensity decreased endoscopic disease activity, significant adverse events deem this regimen unsuitable for future clinical use in patients with refractory Crohn's disease. FUNDING: Efficacy and Mechanism Evaluation Programme, a Medical Research Council and National Institute for Health Research partnership.

Investigating the effect of providing monetary incentives to participants on completion rates of referred co-respondents: An embedded randomized controlled trial.

Background: The use of a second informant (co-respondent) is a common method of identifying potential bias in outcome data (e.g., parent-report child outcomes). There is, however, limited evidence regarding methods of increasing response rates from co-respondents. The use of financial incentives is associated with higher levels of engagement and follow-up data collection in online surveys. This study investigated whether financial incentives paid to index participants in an online trial of a parenting-focused intervention, would lead to higher levels of co-respondent data collection. Methods: A study within a trial (SWAT) using a parallel group RCT design. Participants in the host study (an RCT of an online intervention) were randomised into one of two SWAT arms: received/did not receive a £15 voucher when referred co-respondent completed baseline measures. Primary outcome was completion (No/Yes) of Spence Children's Anxiety Scale (SCAS or SCAS-Pre) at baseline. Additional analysis explored impact of incentives on data quality. Results: Intention to treat analysis of 899 parents (183 co-respondents) in the no-incentive arm, and 911 parents (199 co-respondents) in incentive arm. Nomination of co-respondents was similar between incentive arms. The RR for the incentive arm compared to the no incentive arm was 1.13 (95% CI: 0.91 to 1.41, p = 0.264) indicating that incentives did not impact completion of outcomes by consented co-respondents. There were no indications of different data quality between arms. Discussion: The finding that payment of financial incentives to index participant does not lead to greater levels of co-respondent outcome completion suggests that careful consideration should be made before allocating resources in this way in future trials. Trial registration: The host study was registered at Study Record | ClinicalTrials.gov and the SWAT study was registered in the SWAT Store | The Northern Ireland Network for Trials Methodology Research (qub.ac.uk): SWAT number 143: Filetoupload,1099612,en.pdf (qub.ac.uk).

Undertaking Studies Within A Trial to evaluate recruitment and retention strategies for randomised controlled trials: lessons learnt from the PROMETHEUS research programme.

Background: Randomised controlled trials ('trials') are susceptible to poor participant recruitment and retention. Studies Within A Trial are the strongest methods for testing the effectiveness of strategies to improve recruitment and retention. However, relatively few of these have been conducted. Objectives: PROMoting THE Use of Studies Within A Trial aimed to facilitate at least 25 Studies Within A Trial evaluating recruitment or retention strategies. We share our experience of delivering the PROMoting THE Use of Studies Within A Trial programme, and the lessons learnt for undertaking randomised Studies Within A Trial. Design: A network of 10 Clinical Trials Units and 1 primary care research centre committed to conducting randomised controlled Studies Within A Trial of recruitment and/or retention strategies was established. Promising recruitment and retention strategies were identified from various sources including Cochrane systematic reviews, the Study Within A Trial Repository, and existing prioritisation exercises, which were reviewed by patient and public members to create an initial priority list of seven recruitment and eight retention interventions. Host trial teams could apply for funding and receive support from the PROMoting THE Use of Studies Within A Trial team to undertake Studies Within A Trial. We also tested the feasibility of undertaking co-ordinated Studies Within A Trial, across multiple host trials simultaneously. Setting: Clinical trials unit-based trials recruiting or following up participants in any setting in the United Kingdom were eligible. Participants: Clinical trials unit-based teams undertaking trials in any clinical context in the United Kingdom. Interventions: Funding of up to £5000 and support from the PROMoting THE Use of Studies Within A Trial team to design, implement and report Studies Within A Trial. Main outcome measures: Number of host trials funded. Results: Forty-two Studies Within A Trial were funded (31 host trials), across 12 Clinical Trials Units. The mean cost of a Study Within A Trial was £3535. Twelve Studies Within A Trial tested the same strategy across multiple host trials using a co-ordinated Study Within A Trial design, and four used a factorial design. Two recruitment and five retention strategies were evaluated in more than one host trial. PROMoting THE Use of Studies Within A Trial will add 18% more Studies Within A Trial to the Cochrane systematic review of recruitment strategies, and 79% more Studies Within A Trial to the Cochrane review of retention strategies. For retention, we found that pre-notifying participants by card, letter or e-mail before sending questionnaires was effective, as was the use of pens, and sending personalised text messages to improve questionnaire response. We highlight key lessons learnt to guide others planning Studies Within A Trial, including involving patient and public involvement partners; prioritising and selecting strategies to evaluate and elements to consider when designing a Study Within A Trial; obtaining governance approvals; implementing Studies Within A Trial, including individual and co-ordinated Studies Within A Trials; and reporting Study Within A Trials. Limitations: The COVID-19 pandemic negatively impacted five Studies Within A Trial, being either delayed (n = 2) or prematurely terminated (n = 3). Conclusions: PROMoting THE Use of Studies Within A Trial significantly increased the evidence base for recruitment and retention strategies. When provided with both funding and practical support, host trial teams successfully implemented Studies Within A Trial. Future work: Future research should identify and target gaps in the evidence base, including widening Study Within A Trial uptake, undertaking more complex Studies Within A Trial and translating Study Within A Trial evidence into practice. Study registration: All Studies Within A Trial in the PROMoting THE Use of Studies Within A Trial programme had to be registered with the Northern Ireland Network for Trials Methodology Research Study Within A Trial Repository. Funding: This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 13/55/80) and is published in full in Health Technology Assessment; Vol. 28, No. 2. See the NIHR Funding and Awards website for further award information.

A Study Within A Trial is a research study nested inside a larger 'host trial', promoting the use of Studies Within A Trial aimed to do Study Within A Trial routine practice in clinical trial units by funding and supporting at least 25 Studies Within A Trial. The best way to test health and social care treatments is to do a randomised controlled trial ('trial'), where some patients get the treatment being tested and some do not. The results of different groups are compared to see if the treatment improves care. Recruiting patients and keeping them involved in trials is often very difficult. Research teams often do not know how best to recruit and keep patients engaged as the methods have not been tested to see if they work. The best way to test these methods is by doing a Study Within A Trial. We test a programme of Studies Within A Trial for recruiting and keeping patients engaged in trials. Trial teams were able to apply for funding of up to £5000 and receive support from Promoting the use of Study Within A Trial team to do Studies Within A Trial. We used our experience of doing Studies Within A Trial to outline lessons learnt for doing Studies Within A Trial. We funded 42 Studies Within A Trial and gave teams necessary advice to do them. We significantly increased the knowledge for both recruitment and retention strategies, and found 'pre-notifying' before sending questionnaires, sending pens and personalised text messages were all effective for increasing responses by participants. We tested Studies Within A Trial across several different trials at the same time to find out more quickly whether their methods worked. We highlight key lessons learnt to guide others doing Studies Within A Trial, including involving patient partners; picking the right strategy to test; getting ethical approvals; how to do and report Studies Within A Trial. Promoting the use of studies within a trial was successful and supported more Studies Within A Trial than planned. We hope our experience will support those doing Studies Within A Trial in the future.