Series: Pragmatic trials and real world evidence: Paper 2. Setting, sites, and investigator selection

Validation of the GetReal Trial Tool - Facilitating discussion and understanding more pragmatic design choices and their implications

BACKGROUND

The GetReal Trial Tool is a decision support tool to assess the impact of design choices on generalizability of clinical trials to routine clinical practice, while taking into account the risk of bias, precision, acceptability and operational feasibility. This study describes the validation of the GetReal Trial Tool.

METHODS

Twelve experts took part in the GetReal Trial tool validation using the protocols of 6 trials conducted with pragmatic elements. The tool entails 7 domains with a total of 43 questions. A pooled Kappa statistic (95% CI) using random effects model was estimated using Open Meta (analyst) software. The possible operational challenges were collated and discussed with the trialists that conducted the trials.

RESULTS

Agreement in the design choices made for the trial protocols was >50% for all the trials and all teams reached consensus during discussion. The pooled Kappa statistic (95% CI) was 0.236 (0.154-0.318). The GetReal Trial tool highlighted several operational challenges, of which almost half had been experienced previously by the trialists. Out of 25 additional operational challenges mentioned by the trialists, 76% were already highlighted by the tool. The tool was considered helpful to optimize trials right from the design stage.

CONCLUSION

The GetReal Trial Tool helps to scrutinize the choice of study design in the light of Real World Evidence generation. The tool identifies most of the operational challenges experienced by trialists to date. The tool serves the intended purpose of facilitating discussion and understanding more pragmatic design choices and their implications.

Assessment of the implementation context in preparation for a clinical study of machine-learning algorithms to automate the classification of digital cervical images for cervical cancer screening in resource-constrained settings

Introduction

We assessed the implementation context and image quality in preparation for a clinical study evaluating the effectiveness of automated visual assessment devices within cervical cancer screening of women living without and with HIV.

Methods

We developed a semi-structured questionnaire based on three Consolidated Framework for Implementation Research (CFIR) domains; intervention characteristics, inner setting, and process, in Cape Town, South Africa. Between December 1, 2020, and August 6, 2021, we evaluated two devices: MobileODT handheld colposcope; and a commercially-available cell phone (Samsung A21ST). Colposcopists visually inspected cervical images for technical adequacy. Descriptive analyses were tabulated for quantitative variables, and narrative responses were summarized in the text.

Results

Two colposcopists described the devices as easy to operate, without data loss. The clinical workspace and gynecological workflow were modified to incorporate devices and manage images. Providers believed either device would likely perform better than cytology under most circumstances unless the squamocolumnar junction (SCJ) were not visible, in which case cytology was expected to be better. Image quality (N = 75) from the MobileODT device and cell phone was comparable in terms of achieving good focus (81% vs. 84%), obtaining visibility of the squamous columnar junction (88% vs. 97%), avoiding occlusion (79% vs. 87%), and detection of lesion and range of lesion includes the upper limit (63% vs. 53%) but differed in taking photographs free of glare (100% vs. 24%).

Conclusion

Novel application of the CFIR early in the conduct of the clinical study, including assessment of image quality, highlight real-world factors about intervention characteristics, inner clinical setting, and workflow process that may affect both the clinical study findings and ultimate pace of translating to clinical practice. The application and augmentation of the CFIR in this study context highlighted adaptations needed for the framework to better measure factors relevant to implementing digital interventions.

The GetReal Trial Tool: Design, Assess and Discuss Clinical Drug Trials in Light of RWE Generation

Methodologies incorporating Real World Elements into clinical trial design (also called pragmatic trials) offer an attractive opportunity to assess the effect of a treatment strategy in routine care and as such guide decision making in practice. Uptake of these methods is slow for several reasons, including uncertainty about acceptability of trial results, lack of experience with the methodology and operational challenges. We developed the 'Get Real Trial Tool', an easy-to-use interface, which allows users to assess the impact of design choices on generalisability to routine clinical practice, while taking into account risk of bias, precision, acceptability and operational feasibility. The tool is grounded in the scientific literature on pragmatic trials combined with knowledge of experts from academia, pharmaceutical companies, HTA bodies, patient organisations, and regulators. The aim is to help researchers optimise trial design and facilitate translation of evidence from pragmatic trials to clinical practice. In this paper we describe the development, structure and application of the GetReal Trial Tool.

Rationale for a Clinical Trial That Compares Acute Stroke Rehabilitation at Inpatient Rehabilitation Facilities to Skilled Nursing Facilities: Challenges and Opportunities

In the United States, approximately 400,000 patients with acute stroke are discharged annually to inpatient rehabilitation facilities (IRFs) or skilled nursing facilities (SNFs). Typically, IRFs provide time-intensive therapy for an average of 2-3 weeks, whereas SNFs provide more moderately intensive therapy for 4-5 weeks. The factors that influence discharge to an IRF or SNF are multifactorial and poorly understood. The complexity of these factors in combination with subjective clinical indications contributes to large variations in the use of IRFs and SNFs. This has significant financial implications for health care expenditure, given that stroke rehabilitation at IRFs costs approximately double that at SNFs. To control health care spending without compromising outcomes, the Institute of Medicine has stated that policy reforms that promote more efficient use of IRFs and SNFs are critically needed. A major barrier to the formulation of such policies is the highly variable and low-quality evidence for the comparative effectiveness of IRF- vs SNF-based stroke rehabilitation. The current evidence is limited by the inability of observational data to control for residual confounding, which contributes to substantial uncertainty around any magnitude of benefit for IRF- vs SNF-based care. Furthermore, it is unclear which specific patients would receive the most benefit from each setting. A randomized controlled trial addresses these issues, because random treatment allocation facilitates an equitable distribution of measured and unmeasured confounders. We discuss several measurement, practical, and ethical issues of a trial and provide our rationale for design suggestions that overcome some of these issues.

Patient and healthcare professional experiences of the Salford Lung Studies: qualitative insights for future effectiveness trials

Background

Randomized controlled trials (RCTs) conducted in the routine care setting provide the opportunity to better understand the effectiveness of new medicines but can present recruitment difficulties. An improved understanding of the challenges/opportunities for patient and healthcare professional (HCP) engagement in clinical research is needed to enhance participation and trial experience. In this study, we explored patient and HCP drivers for, and experiences of, participation in the Salford Lung Studies (SLS), and their views on future trial participation and the overall value of such trials.

Methods

This was a qualitative study set in Salford, UK, comprising patient telephone interviews (N = 10) and HCP advisory boards (one with general practitioners [GPs], one with practice managers [PMs]); all individuals had participated in the SLS. Semi-structured telephone interviews were recorded, transcribed and analysed thematically. Advisory board meetings were analysed based on transcriptions of audio recordings and field notes.

Results

For patients, key positive aspects of the SLS were the ease/convenience of study assessments and excellent relationships with study nurses. GPs and PMs considered the SLS to be well-organized and highlighted the value of research nurse support; they also described minor challenges relating to trial systems, initial financial strain on practices and staff turnover. All participants indicated that they were very likely to participate in future trials, citing a design closely aligned with routine care practice as essential. Several strategies to encourage trial participation were suggested, such as clearly communicating benefits to patients and ensuring flexible study assessments.

Conclusions

Patients and HCPs had positive experiences of the SLS. The study design, closely aligned with routine care, was considered important to their high likelihood of participating in future trials. The experiences of patients and HCPs in the SLS provide valuable insights that will help inform future best practice in the design and conduct of future real-world effectiveness RCTs in primary care. The detailed first-hand experiences of HCPs will be of significant value to others considering engaging in clinical research and participating in effectiveness RCTs.

Variation in the observed effect of Xpert MTB/RIF testing for tuberculosis on mortality: A systematic review and analysis of trial design considerations

Background: Most studies evaluating the effect of Xpert MTB/RIF testing for tuberculosis (TB) concluded that it did not reduce overall mortality compared to usual care. We conducted a systematic review to assess whether key study design and execution features contributed to earlier identification of patients with TB and decreased pre-treatment loss to follow-up, thereby reducing the potential impact of Xpert MTB/RIF testing. Methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and Scopus for literature published from 1 st January 2009 to February 2019. We included all primary intervention studies that had evaluated the effect of Xpert MTB/RIF on mortality compared to usual care in participants with presumptive pulmonary TB. We critically reviewed features of included studies across: Study setting and context, Study population, Participant recruitment and enrolment, Study procedures, and Study follow-up. Results: We included seven randomised and one non-randomised study.  All included studies demonstrated relative reductions in overall mortality in the Xpert MTB/RIF arm ranging from 6% to 40%. However, mortality reduction was reported to be statistically significant in two studies. Study features that could explain the lack of observed effect on mortality included: the higher quality of care at study sites; inclusion of patients with a higher pre-test probability of TB leading to higher than expected empirical rates; performance of additional diagnostic testing not done in usual care leading to increased TB diagnosis or empiric treatment initiation; the recruitment of participants likely to return for follow-up; and involvement of study staff in ensuring adherence with care and follow-up. Conclusion: Most studies of Xpert MTB/RIF were designed and conducted in a manner that resulted in more patients being diagnosed and treated for TB, minimising the potential difference in mortality Xpert MTB/RIF testing could have achieved compared to usual care.

Real-World Data and Randomised Controlled Trials: The Salford Lung Study

Traditional efficacy double-blind randomised controlled trials (DBRCTs) measure the benefit a treatment produces under near-ideal test conditions in highly selected patient populations; however, the behaviour of patients and investigators in such trials is highly controlled, highly compliant and adherent, and non-representative of routine clinical practice. Pragmatic effectiveness trials measure the benefit a treatment produces in patients in everyday "real-world" practice. Ideally, effectiveness trials should recruit patients as similar as possible to those who will ultimately be prescribed the medicine, and create freedom within the study design to allow normal behaviours of patients and healthcare professionals (HCPs) to be expressed. The Salford Lung Study (SLS) was a world-first, prospective, phase III, pragmatic randomised controlled trial (RCT) programme in patients with chronic obstructive pulmonary disease and asthma to evaluate the effectiveness of a pre-licensed medication (fluticasone furoate/vilanterol) in real-world practice using electronic health records and through collaboratively engaging general practitioners and community pharmacists in clinical research. The real-world aspect of SLS was unique, requiring careful planning and attention to the goals of maximising the external validity of the trials while maintaining scientific rigour and securing suitable electronic processes for proper interpretation of safety data. Key learnings from SLS that may inform the design of future pragmatic effectiveness RCTs include: (1) ensuring the trial setting and operational infrastructure are aligned with routine clinical care; (2) recruiting a broad patient population with characteristics as close as possible to patients in routine clinical practice, to maximise the generalisability and applicability of trial results; (3) ensuring that patients and HCPs are suitably engaged in the trial, to maximise the chances of successful trial delivery; and (4) careful study design, incorporating outcomes of value to patients, HCPs, policymakers and payers, and using pre-planned analyses to address scientifically valid research hypotheses to ensure robustness of the trial data.

Pragmatic Trials in Genomic Medicine: The Integrating Pharmacogenetics In Clinical Care (I-PICC) Study

Pragmatic clinical trials (PCTs) have an established presence in clinical research and yet have only recently garnered attention within the landscape of genomic medicine. Using the PRagmatic-Explanatory Continuum Indicator Summary 2 (PRECIS-2) as a framework, this paper illustrates the application of PCT principles to The Integrating Pharmacogenetics In Clinical Care (I-PICC) Study, a trial of pharmacogenetic testing prior to statin initiation for cardiovascular disease prevention in primary care. The trial achieved high engagement with providers (85% enrolled of those approached) and enrolled a representative sample of participants for which statin therapy would be recommended. The I-PICC Study has a high level of pragmatism, which should enhance the generalizability of its findings. The PRECIS-2 may be useful in the design and evaluation of PCTs of genomic medicine interventions, contributing to the generation of evidence that can bridge the gap between genomics innovation and clinical adoption.

Variation in the observed effect of Xpert MTB/RIF testing for tuberculosis on mortality: A systematic review and analysis of trial design considerations

Background: Most studies evaluating the effect of Xpert MTB/RIF testing for tuberculosis (TB) concluded that it did not reduce overall mortality compared to usual care. We conducted a systematic review to assess whether key study design and execution features contributed to earlier identification of patients with TB and decreased pre-treatment loss to follow-up, thereby reducing the potential impact of Xpert MTB/RIF testing. Methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and Scopus for literature published from 1 st January 2009 to February 2019. We included all primary intervention studies that had evaluated the effect of Xpert MTB/RIF on mortality compared to usual care in participants with presumptive pulmonary TB. We critically reviewed features of included studies across: Study setting and context, Study population, Participant recruitment and enrolment, Study procedures, and Study follow-up. Results: We included seven randomised and one non-randomised study.  All included studies demonstrated relative reductions in overall mortality in the Xpert MTB/RIF arm ranging from 6% to 40%. However, mortality reduction was reported to be statistically significant in two studies. Study features that could explain the lack of observed effect on mortality included: the higher quality of care at study sites; inclusion of patients with a higher pre-test probability of TB leading to higher than expected empirical rates; performance of additional diagnostic testing not done in usual care leading to increased TB diagnosis or empiric treatment initiation; the recruitment of participants likely to return for follow-up; and involvement of study staff in ensuring adherence with care and follow-up. Conclusion: Most studies of Xpert MTB/RIF were designed and conducted in a manner that resulted in more patients being diagnosed and treated for TB, minimising the potential difference in mortality Xpert MTB/RIF testing could have achieved compared to usual care.

Clinical effectiveness of once-daily fluticasone furoate/umeclidinium/vilanterol in usual practice: the COPD INTREPID study design

Effectiveness studies complement conventional randomised controlled trials by providing a holistic view of treatments in the setting of usual clinical practice. We present the protocol for the ongoing INTREPID (INvestigation of TRelegy Effectiveness: usual PractIce Design; ClinicalTrials.gov identifier: NCT03467425) study, a randomised, open-label, 24-week effectiveness study of once-daily fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI; Trelegy) delivered by the ELLIPTA inhaler versus non-ELLIPTA multiple-inhaler triple therapy in patients with chronic obstructive pulmonary disease (COPD) in usual practice settings. INTREPID was designed to provide evidence of FF/UMEC/VI effectiveness in patients with COPD managed in routine healthcare systems across multiple European countries. Between study initiation and end-of-study visits, patients will receive their medication and care as they would ordinarily receive it, from their usual healthcare provider at their usual healthcare centre. Study-specific intervention will be minimal. The primary end-point will be the proportion of COPD assessment test (CAT) responders, defined as a clinically meaningful improvement from baseline of ≥2 units, at week 24. The CAT was chosen as it provides health status information relevant to patients, physicians, health technology agencies and payers. Lung function (forced expiratory volume in 1 s) and critical inhaler errors will also be assessed in a subgroup of patients. The strengths and weaknesses of the protocol and some of the challenges associated with conducting this multicountry study, such as differences in healthcare systems and treatment practices across sites, will also be discussed.

Acupuncture for cancer pain: protocol for a pilot pragmatic randomised controlled trial

INTRODUCTION

Although acupuncture has been recommended for alleviating cancer pain by clinical guidelines, the level of the supporting evidence needs to be improved. A pragmatic randomised controlled trial (pRCT) in a hospital setting would provide real-world assessments of the overall clinical effects of acupuncture. This pilot trial aims to explore the feasibility and provide data for sample size calculations for a pRCT evaluating the effectiveness of acupuncture as an adjunctive therapy to routine medical care for cancer pain.

METHODS AND ANALYSIS

Thirty patients with cancer admitted to the oncology department with moderate or severe pain will be recruited. Participants will be randomised at a ratio of 1:1 to the adjunctive acupuncture group or a control group which receives routine pain management without acupuncture. The standardised section of the acupuncture protocol will be developed based on the results of reviews of the literature, recommendations in clinical guidelines and interviews with clinical experts. The acupuncturist will be allowed to tailor the protocol according to the individual situation of each participant. Primary outcomes relevant to the feasibility of conducting a fully powered trial include: numbers and proportions of participants recruited, screened, consented and randomised; numbers and reasons for withdrawals and dropouts; numbers and types of adverse events; feasibility of implementing the trial procedures; evaluation of the comprehensiveness and ease-of-use of the case report form. Secondary outcomes are clinical measurements of the effectiveness of the treatment that are intended for use in the full-scale trial. Analysis of feasibility will be descriptive and pain intensity measures will be analysed using mixed-effects regression.

ETHICS AND DISSEMINATION

Ethics approval was obtained from the Institutional Ethics Committee of Guangdong Provincial Hospital of Chinese Medicine (approval no: Z2017-184-01) and RMIT University Human Research Ethics Committee (reference no: 21361). Results will be disseminated in a peer-reviewed journal, and trial participants will be informed via email and/or phone calls.

TRIAL REGISTRATION NUMBER

ChiCTR1800017023.

Pre-trial qualitative work with health care professionals to refine the design and delivery of a randomised controlled trial on kidney care

BACKGROUND

Recruitment to randomised controlled trials (RCTs) is challenging. Pre-trial qualitative research provides insights into the feasibility and acceptability of proposed trial designs and delivery; however, this is rarely conducted. This paper reports on work undertaken in advance of the Prepare for Kidney Care trial (formerly PrepareME), which compares preparing for dialysis with preparing for conservative care for patients with chronic kidney disease. The paper describes how the findings refined plans for the forthcoming trial.

METHODS

Semi-structured interviews were undertaken with health-care professionals involved in delivering or recruiting to the trial. Interview findings were considered in relation to observations of a patient advisory group workshop and introductory site visits, which were set up to present the trial to professionals involved in the internal pilot phase of the RCT. The use of findings and input from multiple sources was intended to support suggested refinements to the forthcoming trial. The findings were fed back to the trial management group and other expert stakeholders.

RESULTS

Sixteen health-care professionals were interviewed, and one patient advisory group workshop and six introductory visits to sites involved in the internal pilot were observed. The professionals interviewed included renal consultants, nurses and renal social workers. Key themes identified from the interviews, supported by the observations, were concerns around the eligibility criteria, the feasibility of the trial intervention, imbalances in the presentation of the trial arms, and anticipated recruitment issues arising from patients' and clinicians' preferences for one arm or the other. Changes to the design were made in response, including to the content of the intervention, the presentation of the trial arms and the name of the RCT.

CONCLUSIONS

This study highlights the value of carrying out pre-trial work with health-care professionals to identify issues with delivering the proposed trial. This work can be particularly valuable in trials of new interventions, for which the barriers to their integration into routine care are unknown. This work has important implications for facilitating the identification of further obstacles in the main RCT. We suggest that pre-trial qualitative work is undertaken to address design issues early on, in addition to ongoing qualitative research to monitor the emergence of obstacles affecting recruitment.

Analysis of nutrition clinical studies involving children in the Middle East and globally

Aim:

To assess pediatric clinical nutrition research by analyzing clinical studies in the Middle East (ME) and globally.

Methods:

Using ClinicalTrials.gov, the numbers of clinical studies in the ME and globally were analyzed.

Results:

The majority of clinical nutrition trials are in North America and Europe. The ME accounts for 4% of all nutrition trials. The majority of pediatric nutrition studies in the ME are in the later phases or are observational and/or epidemiological studies with a focus on poor nutrition or nutrition disorders. Industry funding in the ME is mostly by regional or local companies; few major global companies are involved.

Conclusion:

The ME is not well represented in clinical nutrition studies involving children. Effort should be expended to rectify this.

Nutritional disorders have become an important worldwide disease burden during the last several decades. The development of effective therapies for nutritional disorders requires clinical trials in the affected populations. Our results showed that although the Middle East currently has the highest proportion of children worldwide, it is not well represented in clinical trials on nutritional studies in children. Furthermore, there is suboptimal funding from the multinational nutrition industry. This analysis indicates that there is a reasonable rationale for inclusion of the Middle East in nutritional clinical research in children, and that there is an untapped opportunity for the expansion of clinical research in this region.

Understanding usual care for patients with multimorbidity: baseline data from a cluster-randomised trial of the 3D intervention in primary care

OBJECTIVES

Recent evidence has highlighted the high prevalence and impact of multimorbidity, but the evidence base for improving management is limited. We have tested a new complex intervention for multimorbidity (the 3D model). The paper describes the baseline characteristics of practices and patients in order to establish the external validity of trial participants. It also explores current 'usual primary care' for multimorbidity, against which the 3D intervention was tested.

DESIGN

Analysis of baseline data from patients in a cluster-randomised controlled trial and additional data from practice staff.

SETTING

Primary care in the UK.

PARTICIPANTS

Patients with multimorbidity (n=5253) and 154 practice staff.

PRIMARY AND SECONDARY OUTCOME MEASURES

Using surveys and routinely available data, we compared the characteristics of participating and non-participating practices and participating and non-participating eligible patients.Baseline questionnaire data from patient participants was used to examine participant illness burden, treatment burden and perceptions of receiving patient-centred care. We obtained data about usual care preintervention from practice staff using questionnaires and a structured pro forma.

RESULTS

Participating practices were slightly larger, in less deprived areas, and with slightly higher scores for patient satisfaction compared with non-participating practices. Patients with dementia or learning difficulties were likely to be excluded by their general practitioners, but comparison of participants with non-participants identified only minor differences in characteristics, suggesting that the sample was otherwise representative. Patients reported substantial illness burden, and an important minority reported high treatment burden. Although patients reported relatively high levels of satisfaction with care, many reported not having received potentially important components of care.

CONCLUSION

This trial achieved good levels of external validity. Although patients were generally satisfied with primary care services, there was significant room for improvement in important aspects of care for multimorbidity that are targeted by the 3D intervention.

TRIAL REGISTRATION NUMBER

ISRCTN06180958; Post-results.

The rise of hospitalists: an opportunity for infectious diseases investigators

INTRODUCTION

Despite the essential role played by infectious diseases specialists in patient care, public health, cost-containment, and biomedical research, the field has a substantially higher percentage of vacant positions than other medicine sub-specialties. While much has been written about what this disturbing trend means for patient care, comparatively little attention has been focused on the dire implications for clinical research and the development of novel anti-infective therapy. Areas covered: We examine the ways that hospitalists and infectious disease specialists might collaborate to study emerging diagnostic platforms, novel antimicrobial agents, and strengthen antimicrobial stewardship programs to improve the delivery of high-quality health care. Through the use of PubMed, the manuscript reviews existing collaborations as well as those that might develop in the years to come. Expert commentary: In this paper, we propose potential strategies to confront this emerging problem, focusing on novel collaborations with the hospitalist - the specialist in inpatient medicine - to bolster the pipeline of funding for clinical infectious diseases investigators.

Series: Pragmatic trials and real world evidence: Paper 6. Outcome measures in the real world

Results from pragmatic trials should reflect the comparative treatment effects encountered in patients in real-life clinical practice to guide treatment decisions. Therefore, pragmatic trials should focus on outcomes that are relevant to patients, clinical practice, and treatment choices. This sixth article in the series (see Box) discusses different types of outcomes and their suitability for pragmatic trials, design choices for measuring these outcomes, and their implications and challenges. Measuring outcomes in pragmatic trials should not interfere with real-world clinical practice to ensure generalizability of trial results, and routinely collected outcomes should be prioritized. Typical outcomes include mortality, morbidity, functional status, well-being, and resource use. Surrogate endpoints are typically avoided as primary outcome. It is important to measure outcomes over a relevant time horizon and obtain valid and precise results. As pragmatic trials are often open label, a less subjective outcome can reduce bias. Methods that decrease bias or enhance precision of the results, such as standardization and blinding of outcome assessment, should be considered when a high risk of bias or high variability is expected. The selection of outcomes in pragmatic trials should be relevant for decision making and feasible in terms of executing the trial in the context of interest. Therefore, this should be discussed with all stakeholders as early as feasible to ensure the relevance of study results for decision making in clinical practice and the ability to perform the study.

Series: Pragmatic trials and real world evidence: Paper 3. Patient selection challenges and consequences

This paper addresses challenges of identifying, enrolling, and retaining participants in a trial conducted within a routine care setting. All patients who are potential candidates for the treatments in routine clinical practice should be considered eligible for a pragmatic trial. To ensure generalizability, the recruited sample should have a similar distribution of the treatment effect modifiers as the target population. In practice, this can be best achieved by including-within the selected sites-all patients without further selection. If relevant heterogeneity between subgroups is expected, increasing the relative proportion of the subgroup of patients in the heterogeneous trial could be considered (oversampling) or a separate trial in this subgroup can be planned. Selection will nevertheless occur. Low enrollment and loss to follow-up can introduce selection and can jeopardize validity as well as generalizability. Pragmatic trials are conducted in clinical practice rather than in a dedicated research setting, which could reduce recruitment rates. However, if a trial poses a minimal burden to the physician and the patient and routine clinical practice is maximally adhered to, the participation rate may be high and loss to follow-up will not be a specific problem for pragmatic trials.