Development and validation of a short form psychometric tool assessing the caregiving Challenge of Living with Cystic Fibrosis (CLCF-SF) in a child.

OBJECTIVE: Caring for a child with cystic fibrosis (CF) is a rigorous daily commitment for caregivers and treatment burden is a major concern. We aimed to develop and validate a short form version of a 46-item tool assessing the Challenge of Living with Cystic Fibrosis (CLCF) for clinical or research use. DESIGN: A novel genetic algorithm based on 'evolving' a subset of items from a pre-specified set of criteria, was applied to optimise the tool, using data from 135 families. MAIN OUTCOME MEASURES: Internal reliability and validity were assessed; the latter compared scores to validated tests of parental well-being, markers of treatment burden, and disease severity. RESULTS: The 15-item CLCF-SF demonstrated very good internal consistency [Cronbach's alpha 0.82 (95%CI 0.78-0.87)]. Scores for convergent validity correlated with the Beck Depression Inventory (Rho = 0.48), State Trait Anxiety Inventory (STAI-State, Rho = 0.41; STAI-Trait, Rho = 0.43), Cystic Fibrosis Questionnaire-Revised, lung function (Rho = -0.37), caregiver treatment management (r = 0.48) and child treatment management (r = 0.45), and discriminated between unwell and well children with CF (Mean Difference 5.5, 95%CI 2.5-8.5, p < 0.001), and recent or no hospital admission (MD 3.6, 95%CI 0.25-6.95, p = 0.039). CONCLUSION: The CLCF-SF provides a robust 15-item tool for assessing the challenge of living with a child with CF.

Pilot and feasibility studies: extending the conceptual framework.

In 2016, we published a conceptual framework outlining the conclusions of our work in defining pilot and feasibility studies. Since then, the CONSORT extension to randomised pilot and feasibility trials has been published and there have been further developments in the pilot study landscape. In this paper, we revisit and extend our framework to incorporate the various feasibility pathways open to researchers, which include internal pilot studies. We consider, with examples, when different approaches to feasibility and pilot studies are more effective and efficient, taking into account the pragmatic decisions that may need to be made. The ethical issues involved in pilot studies are discussed. We end with a consideration of the funders' perspective in making difficult resource decisions to include feasibility work and the policy implications of these; throughout, we provide examples of the uncertainties and compromises that researchers have to navigate to make progress in the most efficient way.

Development and preliminary validation of the challenges of living with cystic fibrosis (CLCF) questionnaire: a 46-item measure of treatment burden for parent/carers of children with CF.

OBJECTIVE: Treatments for cystic fibrosis (CF) are complex, labour-intensive, and perceived as highly burdensome by caregivers of children with CF. An instrument assessing burden of care is needed. DESIGN: A stepwise, qualitative design was used to create the CLCF with caregiver focus groups, participant researchers, a multidisciplinary professional panel, and cognitive interviews. MAIN OUTCOME MEASURES: Preliminary psychometric analyses evaluated the reliability and convergent validity of the CLCF scores. Cronbach's alpha assessed internal consistency and t-tests examined test-retest reliability. Correlations measured convergence between the Treatment Burden scale of the Cystic Fibrosis Questionnaire-Revised (CFQ-R) and the CLCF. Discriminant validity was assessed by comparing CLCF scores in one vs two-parent families, across ages, and in children with vs without Pseudomonas aeruginosa (PA). RESULTS: Six Challenge subscales emerged from the qualitative data and the professional panel constructed a scoresheet estimating the Time and Effort required for treatments. Internal consistency and test-retest reliability were adequate. Good convergence was found between the Total Challenge score and Treatment Burden on the CFQ-R (r=-0.49, p = 0.02, n = 31). A recent PA infection signalled higher Total Challenge for caregivers (F(23)11.72, p = 0.002). CONCLUSIONS: The CLCF, developed in partnership with parents/caregivers and CF professionals, is a timely, disease-specific burden measure for clinical research.

Pilot and feasibility studies for pragmatic trials have unique considerations and areas of uncertainty.

BACKGROUND AND OBJECTIVE: Feasibility studies are increasingly being used to support the development of, and investigate uncertainties around, future large-scale trials. The future trial can be designed with either a pragmatic or explanatory mindset. Whereas pragmatic trials aim to inform the choice between different care options and thus, are designed to resemble conditions outside of a clinical trial environment, explanatory trials examine the benefit of a treatment under more controlled conditions. There is existing guidance for designing feasibility studies, but none that explicitly considers the goals of pragmatic designs. We aimed to identify unique areas of uncertainty that are relevant to planning a pragmatic trial. RESULTS: We identified ten relevant domains, partly based on the pragmatic-explanatory continuum indicator summary-2 (PRECIS-2) framework, and describe potential questions of uncertainty within each: intervention development, research ethics, participant identification and eligibility, recruitment of individuals, setting, organization, flexibility of delivery, flexibility of adherence, follow-up, and importance of primary outcome to patients and decision-makers. We present examples to illustrate how uncertainty in these domains might be addressed within a feasibility study. CONCLUSION: Researchers planning a feasibility study in advance of a pragmatic trial should consider feasibility objectives specifically relevant to areas of uncertainty for pragmatic trials.

Progression from external pilot to definitive randomised controlled trial: a methodological review of progression criteria reporting.

OBJECTIVES: Prespecified progression criteria can inform the decision to progress from an external randomised pilot trial to a definitive randomised controlled trial. We assessed the characteristics of progression criteria reported in external randomised pilot trial protocols and results publications, including whether progression criteria were specified a priori and mentioned in prepublication peer reviewer reports. STUDY DESIGN: Methodological review. METHODS: We searched four journals through PubMed: British Medical Journal Open, Pilot and Feasibility Studies, Trials and Public Library of Science One. Eligible publications reported external randomised pilot trial protocols or results, were published between January 2018 and December 2019 and reported progression criteria. We double data extracted 25% of the included publications. Here we report the progression criteria characteristics. RESULTS: We included 160 publications (123 protocols and 37 completed trials). Recruitment and retention were the most frequent indicators contributing to progression criteria. Progression criteria were mostly reported as distinct thresholds (eg, achieving a specific target; 133/160, 83%). Less than a third of the planned and completed pilot trials that included qualitative research reported how these findings would contribute towards progression criteria (34/108, 31%). The publications seldom stated who established the progression criteria (12/160, 7.5%) or provided rationale or justification for progression criteria (44/160, 28%). Most completed pilot trials reported the intention to proceed to a definitive trial (30/37, 81%), but less than half strictly met all of their progression criteria (17/37, 46%). Prepublication peer reviewer reports were available for 153/160 publications (96%). Peer reviewer reports for 86/153 (56%) publications mentioned progression criteria, with peer reviewers of 35 publications commenting that progression criteria appeared not to be specified. CONCLUSIONS: Many external randomised pilot trial publications did not adequately report or propose prespecified progression criteria to inform whether to proceed to a future definitive randomised controlled trial.

Transparency of informed consent in pilot and feasibility studies is inadequate: a single-center quality assurance study.

BACKGROUND: Pilot and feasibility studies (PAFS) often have complex objectives aimed at assessing feasibility of conducting a larger study. These may not be clear to participants in pilot studies. METHODS: Here, we aimed to assess the transparency of informed consent in PAFS by investigating whether researchers communicate, through patient information leaflets and consent forms, key features of the studies. We collected this data from original versions of these documents submitted for ethics approval and the final approved documents for PAFS submitted to the Hamilton Integrated Research Ethics Board, Canada. RESULTS: One hundred eighty-four PAFS, submitted for ethics approval from 2004 to 2020, were included, and we found that of the approved consent documents which were provided to participants, 83.2% (153) stated the terms "pilot" or "feasibility" in their title, 12% (22) stated the definition of a pilot/feasibility study, 42.4% (78) of the studies stated their intent to assess feasibility, 19.6% (36) stated the specific feasibility objectives, 1.6% (3) stated the criteria for success of the pilot study, and 0.5% (1) stated all five of these criteria. After ethics review, a small increase in transparency occurred, ranging from 1.6 to 2.8% depending on the criteria. By extracting data from the protocols of the PAFS, we found that 73.9% (136) stated intent to assess feasibility, 71.2% (131) stated specific feasibility objectives, and 33.7% (62) stated criteria for success of the study to lead to a larger study. CONCLUSION: The transparency of informed consent in PAFS is inadequate and needs to be specifically addressed by research ethics guidelines. Research ethics boards and researchers ought to be made aware and mindful of best practices of informed consent in the context of PAFS.

Assessing the transparency of informed consent in feasibility and pilot studies: a single-centre quality assurance study protocol.

INTRODUCTION: Pilot/feasibility studies assess the feasibility of conducting a larger study. Although researchers ought to communicate the feasibility objectives to their participants, many research ethics guidelines do not comment on how informed consent applies to pilot studies. It is unclear whether researchers and research ethics boards clearly communicate the purpose of pilot studies to participants consenting.The primary objective of this study is to assess whether pilot/feasibility studies submitted for ethics approval to a research ethics board transparently communicate the purpose of the study to participants through their informed consent practice. A highly transparent consent practice entails the consent documents communicate: (1) the term 'pilot' or 'feasibility' in the title; (2) the definition of a pilot/feasibility study; (3) the primary objectives of the study are to assess feasibility; (4) the specific feasibility objectives; and (5) the criteria for the study to successfully lead to the main study. The secondary objectives are to assess whether there is a difference between submitted and revised versions of the consent documents (revisions are made to obtain research ethics approval), to determine factors associated with transparent consent practices and to assess the consistency with which pilot and feasibility studies assess feasibility outcomes as their primary objectives. METHODS AND ANALYSIS: This is a retrospective review of informed consent information for pilot/feasibility studies submitted to the Hamilton integrated Research Ethics Board, Canada. We will look at submitted and revised consent documents for pilot/feasibility studies submitted over a 14-year period. We will use descriptive statistics to summarise data, reporting results as percentages with 95% CIs, and conduct logistic regression to determine characteristics associated with transparent consent practices. ETHICS AND DISSEMINATION: The study protocol was approved by the Hamilton integrated Research Ethics Board, and the results of this study will be submitted for publication in a peer-reviewed journal.

Guidelines for reporting non-randomised pilot and feasibility studies.

As the number of submissions to Pilot and Feasibility Studies increases, there is a need for good quality reporting guidelines to help researchers tailor their reports in a way that is consistent and helpful to other readers. The publication in 2016 of the CONSORT extension to pilot and feasibility trials filled a much-needed gap, but there still remains some uncertainty as to how to report pilot and feasibility studies that are not randomised. This editorial aims to provide some general guidance on how to report the most common types of non-randomised pilot and feasibility studies that are submitted to the journal. We recommend using the CONSORT extension to pilot and feasibility trials as the main reference document-it includes detailed elaboration and explanation of each item, and in most cases, simple adaptation, or non-use of items that are not applicable, will suffice. Several checklists found on the Equator website may provide helpful supplementary guidance, when used alongside the CONSORT extension, and we give some examples.

Creation of the WHO Indicators of Infant and Young Child Development (IYCD): metadata synthesis across 10 countries.

BACKGROUND: Renewed global commitment to the improvement of early child development outcomes, as evidenced by the focus of the United Nations Sustainable Development Goal 4, highlights an increased need for reliable and valid measures to evaluate preventive and interventional efforts designed to affect change. Our objective was to create a new tool, applicable across multicultures, to measure development from 0 to 3 years through metadata synthesis. METHODS: Fourteen cross-sectional data sets were contributed on 21 083 children from 10 low/middle-income countries (LMIC), assessed using seven different tools (caregiver reported or directly assessed). Item groups, measuring similar developmental skills, were identified by item mapping across tools. Logistic regression curves displayed developmental trajectories for item groups across countries and age. Following expert consensus to identify well-performing items across developmental domains, a second mapping exercise was conducted to fill any gaps across the age range. The first version of the tool was constructed. Item response analysis validated our approach by putting all data sets onto a common scale. RESULTS: 789 individual items were identified across tools in the first mapping and 129 item groups selected for analysis. 70 item groups were then selected through consensus, based on statistical performance and perceived importance, with a further 50 items identified at second mapping. A tool comprising 120 items (23 fine motor, 23 gross motor, 20 receptive language, 24 expressive language, 30 socioemotional) was created. The linked data sets on a common scale showed a curvilinear trajectory of child development, highlighting the validity of our approach through excellent coverage by age and consistency of measurement across contributed tools, a novel finding in itself. CONCLUSIONS: We have created the first version of a prototype tool for measuring children in the early years, developed using novel easy to apply methodology; now it needs to be feasibility tested and piloted across several LMICs.

Pilot trials in physical activity journals: a review of reporting and editorial policy.

BACKGROUND: Since the early 2000s, a number of publications in the medical literature have highlighted inadequacies in the design, conduct and reporting of pilot trials. This work led to two notable publications in 2016: a conceptual framework for defining feasibility studies and an extension to the CONSORT 2010 statement to include pilot trials. It was hoped that these publications would educate researchers, leading to better use of pilot trials and thus more rigorously planned and informed randomised controlled trials. The aim of the present work is to evaluate the impact of these publications in the field of physical activity by reviewing the literature pre- and post-2016. This first article presents the pre-2016 review of the reporting and the current editorial policy applied to pilot trials published in physical activity journals. METHODS: Fourteen physical activity journals were screened for pilot and feasibility studies published between 2012 and 2015. The CONSORT 2010 extension to pilot and feasibility studies was used as a framework to assess the reporting quality of the studies. Editors of the eligible physical activity journals were canvassed regarding their editorial policy for pilot and feasibility studies. RESULTS: Thirty-one articles across five journals met the eligibility criteria. These articles fell into three distinct categories: trials that were carried out in preparation for a future definitive trial (23%), trials that evaluated the feasibility of a novel intervention but did not explicitly address a future definitive trial (23%) and trials that did not have any clear objectives to address feasibility (55%). Editors from all five journals stated that they generally do not accept pilot trials, and none gave reference to the CONSORT 2010 extension as a guideline for submissions. CONCLUSION: The result that over half of the studies did not have feasibility objectives is in line with previous research findings, demonstrating that these findings are not being disseminated effectively to researchers in the field of physical activity. The low standard of reporting across most reviewed articles and the neglect of the extended CONSORT 2010 statement by the journal editors highlight the need to actively disseminate these guidelines to ensure their impact.

A mixed methods study to evaluate the feasibility of using the Adolescent Diabetes Needs Assessment Tool App in paediatric diabetes care in preparation for a longitudinal cohort study.

BACKGROUND: An evaluation study was carried out to determine the feasibility of integrating the Adolescent Diabetes Needs Assessment Tool (ADNAT) App into UK paediatric diabetes care, to ascertain best practice standards and to determine methodological recommendations for a future cohort study. METHODS: A non-randomised, cohort, mixed methods study design was used to ensure equality of access to ADNAT for all participants at three sites in the North West of England. Following UK Medical Research Council guidance, the RE-AIM (reach, effectiveness (potential and perceived), adoption, implementation, maintenance) framework was used to guide study objectives and feasibility outcomes. Patients who completed ADNAT (completers) were compared with those who failed to complete (non-completers). Patients' glycaemic control (HbA1c) was accessed from their clinical data at baseline and at 6 months, alongside their ADNAT scores which were correlated with changes in HbA1c levels. The diabetes teams (respondents) completed a web-based survey and attended focus group interviews. RESULTS: Eighty-nine patients were recruited. Withdrawal rates were low at 4.5% (n = 4). Forty-four patients (49.4%) completed ADNAT, leaving 45 (50.6%) non-completers. There were large baseline differences in HbA1c and variable rates of change at 6 months. After adjusting for baseline HbA1C and site in an analysis of covariance, completers had a lower post-ADNAT mean HbA1C level than non-completers at 6 months (-5.42 mmol/mol, 95% CI -11.48, 0.64). Patients' glycaemic control (HbA1c) at 6 months correlated reasonably well with their ADNAT scores (Spearman's rho = 0.46). Survey and focus group data showed that ADNAT was judged to be an effective clinical tool by the diabetes teams. Value to patients was perceived by the teams to be linked to parental support, age and previous diabetes education. The combined data triangulated. It served to capture different dimensions which were used to define changes to achieve practice standards and methodological recommendations. CONCLUSIONS: The combined data showed that ADNAT has the potential to be a clinically viable tool. It has demonstrated the need for a randomised design that is tailored for a 'hard to reach' adolescent population. A cluster randomised controlled trial that involves sequential but random rollout of ADNAT over multiple time periods may be the most appropriate and is currently being considered for the larger study. TRIAL REGISTRATION: NIHR Children's Clinical Research Network, UKCRN ID 6633.

Sample size re-estimation in paired comparative diagnostic accuracy studies with a binary response.

BACKGROUND: The sample size required to power a study to a nominal level in a paired comparative diagnostic accuracy study, i.e. studies in which the diagnostic accuracy of two testing procedures is compared relative to a gold standard, depends on the conditional dependence between the two tests - the lower the dependence the greater the sample size required. A priori, we usually do not know the dependence between the two tests and thus cannot determine the exact sample size required. One option is to use the implied sample size for the maximal negative dependence, giving the largest possible sample size. However, this is potentially wasteful of resources and unnecessarily burdensome on study participants as the study is likely to be overpowered. A more accurate estimate of the sample size can be determined at a planned interim analysis point where the sample size is re-estimated. METHODS: This paper discusses a sample size estimation and re-estimation method based on the maximum likelihood estimates, under an implied multinomial model, of the observed values of conditional dependence between the two tests and, if required, prevalence, at a planned interim. The method is illustrated by comparing the accuracy of two procedures for the detection of pancreatic cancer, one procedure using the standard battery of tests, and the other using the standard battery with the addition of a PET/CT scan all relative to the gold standard of a cell biopsy. Simulation of the proposed method illustrates its robustness under various conditions. RESULTS: The results show that the type I error rate of the overall experiment is stable using our suggested method and that the type II error rate is close to or above nominal. Furthermore, the instances in which the type II error rate is above nominal are in the situations where the lowest sample size is required, meaning a lower impact on the actual number of participants recruited. CONCLUSION: We recommend multinomial model maximum likelihood estimation of the conditional dependence between paired diagnostic accuracy tests at an interim to reduce the number of participants required to power the study to at least the nominal level. TRIAL REGISTRATION: ISRCTN ISRCTN73852054 . Registered 9th of January 2015. Retrospectively registered.

Erratum to: Methods and processes for development of a CONSORT extension for reporting pilot randomized controlled trials.

[This corrects the article DOI: 10.1186/s40814-016-0065-z.].

Methods and processes for development of a CONSORT extension for reporting pilot randomized controlled trials.

BACKGROUND: Feasibility and pilot studies are essential components of planning or preparing for a larger randomized controlled trial (RCT). They are intended to provide useful information about the feasibility of the main RCT-with the goal of reducing uncertainty and thereby increasing the chance of successfully conducting the main RCT. However, research has shown that there are serious inadequacies in the reporting of pilot and feasibility studies. Reasons for this include a lack of explicit publication policies for pilot and feasibility studies in many journals, unclear definitions of what constitutes a pilot or feasibility RCT/study, and a lack of clarity in the objectives and methodological focus. All these suggest that there is an urgent need for new guidelines for reporting pilot and feasibility studies. OBJECTIVES: The aim of this paper is to describe the methods and processes in our development of an extension to the Consolidated Standards of Reporting Trials (CONSORT) Statement for reporting pilot and feasibility RCTs, that are executed in preparation for a future, more definitive RCT. METHODS/DESIGN: There were five overlapping parts to the project: (i) the project launch-which involved establishing a working group and conducting a review of the literature; (ii) stakeholder engagement-which entailed consultation with the CONSORT group, journal editors and publishers, the clinical trials community, and funders; (iii) a Delphi process-used to assess the agreement of experts on initial definitions and to generate a reporting checklist for pilot RCTs, based on the 2010 CONSORT statement extension applicable to reporting pilot studies; (iv) a consensus meeting-to discuss, add, remove, or modify checklist items, with input from experts in the field; and (v) write-up and implementation-which included a guideline document which gives an explanation and elaboration (E&E) and which will provide advice for each item, together with examples of good reporting practice. This final part also included a plan for dissemination and publication of the guideline. CONCLUSIONS: We anticipate that implementation of our guideline will improve the reporting completeness, transparency, and quality of pilot RCTs, and hence benefit several constituencies, including authors of journal manuscripts, funding agencies, educators, researchers, and end-users.

CONSORT 2010 statement: extension to randomised pilot and feasibility trials.

The Consolidated Standards of Reporting Trials (CONSORT) statement is a guideline designed to improve the transparency and quality of the reporting of randomised controlled trials (RCTs). In this article we present an extension to that statement for randomised pilot and feasibility trials conducted in advance of a future definitive RCT. The checklist applies to any randomised study in which a future definitive RCT, or part of it, is conducted on a smaller scale, regardless of its design (eg, cluster, factorial, crossover) or the terms used by authors to describe the study (eg, pilot, feasibility, trial, study). The extension does not directly apply to internal pilot studies built into the design of a main trial, non-randomised pilot and feasibility studies, or phase II studies, but these studies all have some similarities to randomised pilot and feasibility studies and so many of the principles might also apply. The development of the extension was motivated by the growing number of studies described as feasibility or pilot studies and by research that has identified weaknesses in their reporting and conduct. We followed recommended good practice to develop the extension, including carrying out a Delphi survey, holding a consensus meeting and research team meetings, and piloting the checklist. The aims and objectives of pilot and feasibility randomised studies differ from those of other randomised trials. Consequently, although much of the information to be reported in these trials is similar to those in randomised controlled trials (RCTs) assessing effectiveness and efficacy, there are some key differences in the type of information and in the appropriate interpretation of standard CONSORT reporting items. We have retained some of the original CONSORT statement items, but most have been adapted, some removed, and new items added. The new items cover how participants were identified and consent obtained; if applicable, the prespecified criteria used to judge whether or how to proceed with a future definitive RCT; if relevant, other important unintended consequences; implications for progression from pilot to future definitive RCT, including any proposed amendments; and ethical approval or approval by a research review committee confirmed with a reference number. This article includes the 26 item checklist, a separate checklist for the abstract, a template for a CONSORT flowchart for these studies, and an explanation of the changes made and supporting examples. We believe that routine use of this proposed extension to the CONSORT statement will result in improvements in the reporting of pilot trials. Editor's note: In order to encourage its wide dissemination this article is freely accessible on the BMJ and Pilot and Feasibility Studies journal websites.

Defining Feasibility and Pilot Studies in Preparation for Randomised Controlled Trials: Development of a Conceptual Framework.

We describe a framework for defining pilot and feasibility studies focusing on studies conducted in preparation for a randomised controlled trial. To develop the framework, we undertook a Delphi survey; ran an open meeting at a trial methodology conference; conducted a review of definitions outside the health research context; consulted experts at an international consensus meeting; and reviewed 27 empirical pilot or feasibility studies. We initially adopted mutually exclusive definitions of pilot and feasibility studies. However, some Delphi survey respondents and the majority of open meeting attendees disagreed with the idea of mutually exclusive definitions. Their viewpoint was supported by definitions outside the health research context, the use of the terms 'pilot' and 'feasibility' in the literature, and participants at the international consensus meeting. In our framework, pilot studies are a subset of feasibility studies, rather than the two being mutually exclusive. A feasibility study asks whether something can be done, should we proceed with it, and if so, how. A pilot study asks the same questions but also has a specific design feature: in a pilot study a future study, or part of a future study, is conducted on a smaller scale. We suggest that to facilitate their identification, these studies should be clearly identified using the terms 'feasibility' or 'pilot' as appropriate. This should include feasibility studies that are largely qualitative; we found these difficult to identify in electronic searches because researchers rarely used the term 'feasibility' in the title or abstract of such studies. Investigators should also report appropriate objectives and methods related to feasibility; and give clear confirmation that their study is in preparation for a future randomised controlled trial designed to assess the effect of an intervention.

Item response theory and structural equation modelling for ordinal data: Describing the relationship between KIDSCREEN and Life-H.

Both item response theory and structural equation models are useful in the analysis of ordered categorical responses from health assessment questionnaires. We highlight the advantages and disadvantages of the item response theory and structural equation modelling approaches to modelling ordinal data, from within a community health setting. Using data from the SPARCLE project focussing on children with cerebral palsy, this paper investigates the relationship between two ordinal rating scales, the KIDSCREEN, which measures quality-of-life, and Life-H, which measures participation. Practical issues relating to fitting models, such as non-positive definite observed or fitted correlation matrices, and approaches to assessing model fit are discussed. item response theory models allow properties such as the conditional independence of particular domains of a measurement instrument to be assessed. When, as with the SPARCLE data, the latent traits are multidimensional, structural equation models generally provide a much more convenient modelling framework.

How big should the pilot study for my cluster randomised trial be?

There is currently a lot of interest in pilot studies conducted in preparation for randomised controlled trials. This paper focuses on sample size requirements for external pilot studies for cluster randomised trials. We consider how large an external pilot study needs to be to assess key parameters for input to the main trial sample size calculation when the primary outcome is continuous, and to estimate rates, for example recruitment rates, with reasonable precision. We used simulation to provide the distribution of the expected number of clusters for the main trial under different assumptions about the natural cluster size, intra-cluster correlation, eventual cluster size in the main trial, and various decisions made at the piloting stage. We chose intra-cluster correlation values and pilot study size to reflect those commonly reported in the literature. Our results show that estimates of sample size required for the main trial are likely to be biased downwards and very imprecise unless the pilot study includes large numbers of clusters and individual participants. We conclude that pilot studies will usually be too small to estimate parameters required for estimating a sample size for a main cluster randomised trial (e.g. the intra-cluster correlation coefficient) with sufficient precision and too small to provide reliable estimates of rates for process measures such as recruitment or follow-up rates.

Pilot and feasibility studies come of age!

This editorial introduces the new, online, open-access journal Pilot and Feasibility Studies. The journal considers manuscripts on any aspect of the design and analysis of pilot and feasibility studies, as well as protocols for pilot and feasibility studies, and discussions and reviews of methodological issues around the planning and reporting of such studies. These studies are generally carried out in preparation for future large-scale definitive randomised controlled trials or observational studies and address key issues of uncertainty. Objectives for conducting pilot and feasibility studies therefore differ from those of the future large-scale study and should be clearly expressed. The journal provides a dedicated place for publication of this important work as well as a forum for discussion of methodological issues that will lead to increased scientific rigour in this area.