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BACKGROUND: Early phase dose-finding (EPDF) trials are crucial for the development of a new intervention and influence whether it should be investigated in further trials. Guidance exists for clinical trial protocols and completed trial reports in the SPIRIT and CONSORT guidelines, respectively. However, both guidelines and their extensions do not adequately address the characteristics of EPDF trials. Building on the SPIRIT and CONSORT checklists, the DEFINE study aims to develop international consensus-driven guidelines for EPDF trial protocols (SPIRIT-DEFINE) and reports (CONSORT-DEFINE). METHODS: The initial generation of candidate items was informed by reviewing published EPDF trial reports. The early draft items were refined further through a review of the published and grey literature, analysis of real-world examples, citation and reference searches, and expert recommendations, followed by a two-round modified Delphi process. Patient and public involvement and engagement (PPIE) was pursued concurrently with the quantitative and thematic analysis of Delphi participants' feedback. RESULTS: The Delphi survey included 79 new or modified SPIRIT-DEFINE (n = 36) and CONSORT-DEFINE (n = 43) extension candidate items. In Round One, 206 interdisciplinary stakeholders from 24 countries voted and 151 stakeholders voted in Round Two. Following Round One feedback, one item for CONSORT-DEFINE was added in Round Two. Of the 80 items, 60 met the threshold for inclusion (≥ 70% of respondents voted critical: 26 SPIRIT-DEFINE, 34 CONSORT-DEFINE), with the remaining 20 items to be further discussed at the consensus meeting. The parallel PPIE work resulted in the development of an EPDF lay summary toolkit consisting of a template with guidance notes and an exemplar. CONCLUSIONS: By detailing the development journey of the DEFINE study and the decisions undertaken, we envision that this will enhance understanding and help researchers in the development of future guidelines. The SPIRIT-DEFINE and CONSORT-DEFINE guidelines will allow investigators to effectively address essential items that should be present in EPDF trial protocols and reports, thereby promoting transparency, comprehensiveness, and reproducibility. TRIAL REGISTRATION: SPIRIT-DEFINE and CONSORT-DEFINE are registered with the EQUATOR Network ( https://www.equator-network.org/ ).
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Lista de Checagem , Projetos de Pesquisa , Humanos , Consenso , Reprodutibilidade dos Testes , Relatório de PesquisaRESUMO
BACKGROUND: Metastatic castration-resistant prostate cancer is enriched in DNA damage response (DDR) gene aberrations. The TOPARP-B trial aims to prospectively validate the association between DDR gene aberrations and response to olaparib in metastatic castration-resistant prostate cancer. METHODS: In this open-label, investigator-initiated, randomised phase 2 trial following a selection (or pick-the-winner) design, we recruited participants from 17 UK hospitals. Men aged 18 years or older with progressing metastatic castration-resistant prostate cancer previously treated with one or two taxane chemotherapy regimens and with an Eastern Cooperative Oncology Group performance status of 2 or less had tumour biopsies tested with targeted sequencing. Patients with DDR gene aberrations were randomly assigned (1:1) by a computer-generated minimisation method, with balancing for circulating tumour cell count at screening, to receive 400 mg or 300 mg olaparib twice daily, given continuously in 4-week cycles until disease progression or unacceptable toxicity. Neither participants nor investigators were masked to dose allocation. The primary endpoint of confirmed response was defined as a composite of all patients presenting with any of the following outcomes: radiological objective response (as assessed by Response Evaluation Criteria in Solid Tumors 1.1), a decrease in prostate-specific antigen (PSA) of 50% or more (PSA50) from baseline, or conversion of circulating tumour cell count (from ≥5 cells per 7·5 mL blood at baseline to <5 cells per 7·5 mL blood). A confirmed response in a consecutive assessment after at least 4 weeks was required for each component. The primary analysis was done in the evaluable population. If at least 19 (43%) of 44 evaluable patients in a dose cohort responded, then the dose cohort would be considered successful. Safety was assessed in all patients who received at least one dose of olaparib. This trial is registered at ClinicalTrials.gov, NCT01682772. Recruitment for the trial has completed and follow-up is ongoing. FINDINGS: 711 patients consented for targeted screening between April 1, 2015, and Aug 30, 2018. 161 patients had DDR gene aberrations, 98 of whom were randomly assigned and treated (49 patients for each olaparib dose), with 92 evaluable for the primary endpoint (46 patients for each olaparib dose). Median follow-up was 24·8 months (IQR 16·7-35·9). Confirmed composite response was achieved in 25 (54·3%; 95% CI 39·0-69·1) of 46 evaluable patients in the 400 mg cohort, and 18 (39·1%; 25·1-54·6) of 46 evaluable patients in the 300 mg cohort. Radiological response was achieved in eight (24·2%; 11·1-42·3) of 33 evaluable patients in the 400 mg cohort and six (16·2%; 6·2-32·0) of 37 in the 300 mg cohort; PSA50 response was achieved in 17 (37·0%; 23·2-52·5) of 46 and 13 (30·2%; 17·2-46·1) of 43; and circulating tumour cell count conversion was achieved in 15 (53·6%; 33·9-72·5) of 28 and 13 (48·1%; 28·7-68·1) of 27. The most common grade 3-4 adverse event in both cohorts was anaemia (15 [31%] of 49 patients in the 300 mg cohort and 18 [37%] of 49 in the 400 mg cohort). 19 serious adverse reactions were reported in 13 patients. One death possibly related to treatment (myocardial infarction) occurred after 11 days of treatment in the 300 mg cohort. INTERPRETATION: Olaparib has antitumour activity against metastatic castration-resistant prostate cancer with DDR gene aberrations, supporting the implementation of genomic stratification of metastatic castration-resistant prostate cancer in clinical practice. FUNDING: Cancer Research UK, AstraZeneca, Prostate Cancer UK, the Prostate Cancer Foundation, the Experimental Cancer Medicine Centres Network, and the National Institute for Health Research Biomedical Research Centres.
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Biomarcadores Tumorais/genética , Enzimas Reparadoras do DNA/genética , Mutação , Ftalazinas/uso terapêutico , Piperazinas/uso terapêutico , Inibidores de Poli(ADP-Ribose) Polimerases/uso terapêutico , Neoplasias de Próstata Resistentes à Castração/tratamento farmacológico , Idoso , Estudos de Coortes , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico , Neoplasias de Próstata Resistentes à Castração/genética , Neoplasias de Próstata Resistentes à Castração/patologia , Taxa de SobrevidaRESUMO
BACKGROUND: the risk factors for and frequency of antibiotic prescription and antibiotic-associated diarrhoea (AAD) among care home residents are unknown. AIM: to prospectively study frequency and risks for antibiotic prescribing and AAD for care home residents. DESIGN AND SETTING: a 12-month prospective cohort study in care homes across South Wales. METHOD: antibiotic prescriptions and the development of AAD were recorded on case report forms. We defined AAD as three or more loose stools in a 24-h period occurring within 8 weeks of exposure to an antibiotic. RESULTS: we recruited 279 residents from 10 care homes. The incidence of antibiotic prescriptions was 2.16 prescriptions per resident year (95% CI: 1.90-2.46). Antibiotics were less likely to be prescribed to residents from dual-registered homes (OR compared with nursing homes: 0.38, 95% CI: 0.18-0.79). For those who were prescribed antibiotics, the incidence of AAD was 0.57 episodes per resident year (95% CI: 0.41-0.81 episodes). AAD was more likely in residents who were prescribed co-amoxiclav (hazards ratio, HR = 2.08, 95% confidence interval, CI: 1.18-3.66) or routinely used incontinence pads (HR = 2.54, 95% CI: 1.26-5.13) and less likely in residents from residential homes (HR compared with nursing homes: 0.14, 95% CI: 0.06-0.32). CONCLUSION: residents of care homes, particularly of nursing homes, are frequently prescribed antibiotics and often experience diarrhoea following such prescriptions. Co-amoxiclav is associated with greater risk of AAD.
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Antibacterianos/efeitos adversos , Diarreia/induzido quimicamente , Instituição de Longa Permanência para Idosos , Casas de Saúde , Padrões de Prática Médica , Idoso , Idoso de 80 Anos ou mais , Combinação Amoxicilina e Clavulanato de Potássio/efeitos adversos , Diarreia/diagnóstico , Diarreia/microbiologia , Prescrições de Medicamentos , Revisão de Uso de Medicamentos , Feminino , Microbioma Gastrointestinal/efeitos dos fármacos , Humanos , Modelos Logísticos , Masculino , Análise Multivariada , Razão de Chances , Modelos de Riscos Proporcionais , Estudos Prospectivos , Fatores de Risco , Fatores de Tempo , País de GalesRESUMO
BACKGROUND: PTEN loss and aberrations in PI3K/AKT signaling kinases associate with poorer response to abiraterone acetate (AA) in metastatic castration-resistant prostate cancer (mCRPC). In this study, we assessed antitumor activity of the AKT inhibitor capivasertib combined with enzalutamide in mCRPC with prior progression on AA and docetaxel. METHODS: This double-blind, placebo-controlled, randomized phase 2 trial, recruited men ≥ 18 years with progressing mCRPC and performance status 0-2 from 15 UK centers. Randomized participants (1:1) received enzalutamide (160 mg orally, once daily) with capivasertib (400 mg)/ placebo orally, twice daily on an intermittent (4 days on, 3 days off) schedule. Primary endpoint was composite response rate (RR): RECIST 1.1 objective response, ≥ 50 % PSA decrease from baseline, or circulating tumor cell count conversion (from ≥ 5 at baseline to < 5 cells/7.5 mL). Subgroup analyses by PTENIHC status were pre-planned. RESULTS: Overall, 100 participants were randomized (50:50); 95 were evaluable for primary endpoint (47:48); median follow-up was 43 months. RR were 9/47 (19.1 %) enzalutamide/capivasertib and 9/48 (18.8 %) enzalutamide/placebo (absolute difference 0.4 % 90 %CI -12.8 to 13.6, p = 0.58), with similar results in the PTENIHC loss subgroup. Irrespective of treatment, OS was significantly worse for PTENIHC loss (10.1 months [95 %CI: 4.6-13.9] vs 14.8 months [95 %CI: 10.8-18]; p = 0.02). Most common treatment-emergent grade ≥ 3 adverse events for the combination were diarrhea (13 % vs 2 %) and fatigue (10 % vs 6 %). CONCLUSIONS: Combined capivasertib/enzalutamide was well tolerated but didn't significantly improve outcomes from abiraterone pre-treated mCRPC.
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Protocolos de Quimioterapia Combinada Antineoplásica , Benzamidas , Docetaxel , Nitrilas , Feniltioidantoína , Neoplasias de Próstata Resistentes à Castração , Pirimidinas , Humanos , Masculino , Neoplasias de Próstata Resistentes à Castração/tratamento farmacológico , Neoplasias de Próstata Resistentes à Castração/patologia , Feniltioidantoína/administração & dosagem , Feniltioidantoína/uso terapêutico , Feniltioidantoína/efeitos adversos , Docetaxel/administração & dosagem , Docetaxel/uso terapêutico , Idoso , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Pessoa de Meia-Idade , Método Duplo-Cego , Pirimidinas/uso terapêutico , Pirimidinas/administração & dosagem , Pirimidinas/efeitos adversos , Androstenos/uso terapêutico , Androstenos/administração & dosagem , Idoso de 80 Anos ou mais , PirróisRESUMO
INTRODUCTION: Early phase dose-finding (EPDF) studies are critical for the development of new treatments, directly influencing whether compounds or interventions can be investigated in further trials to confirm their safety and efficacy. There exists guidance for clinical trial protocols and reporting of completed trials in the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) 2013 and CONsolidated Standards Of Reporting Randomised Trials (CONSORT) 2010 statements. However, neither the original statements nor their extensions adequately cover the specific features of EPDF trials. The DEFINE (DosE-FIndiNg Extensions) study aims to enhance transparency, completeness, reproducibility and interpretation of EPDF trial protocols (SPIRIT-DEFINE) and their reports once completed (CONSORT-DEFINE), across all disease areas, building on the original SPIRIT 2013 and CONSORT 2010 statements. METHODS AND ANALYSIS: A methodological review of published EPDF trials will be conducted to identify features and deficiencies in reporting and inform the initial generation of the candidate items. The early draft checklists will be enriched through a review of published and grey literature, real-world examples analysis, citation and reference searches and consultation with international experts, including regulators and journal editors. Development of CONSORT-DEFINE commenced in March 2021, followed by SPIRIT-DEFINE from January 2022. A modified Delphi process, involving worldwide, multidisciplinary and cross-sector key stakeholders, will be run to refine the checklists. An international consensus meeting in autumn 2022 will finalise the list of items to be included in both guidance extensions. ETHICS AND DISSEMINATION: This project was approved by ICR's Committee for Clinical Research. The Health Research Authority confirmed Research Ethics Approval is not required. The dissemination strategy aims to maximise guideline awareness and uptake, including but not limited to dissemination in stakeholder meetings, conferences, peer-reviewed publications and on the EQUATOR Network and DEFINE study websites. REGISTRATION DETAILS: SPIRIT-DEFINE and CONSORT-DEFINE are registered with the EQUATOR Network.
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Lista de Checagem , Projetos de Pesquisa , Humanos , Padrões de Referência , Reprodutibilidade dos Testes , Literatura de Revisão como Assunto , Conferências de Consenso como AssuntoRESUMO
BACKGROUND: Data suggest that approximately 50,000 adults with learning disabilities (LDs) in England and Wales are currently prescribed antipsychotic medication. Illness in this population is common, including significant rates of challenging behaviour and mental illness, but there is particular concern over the use of antipsychotics prescribed for reasons other than the treatment of psychosis. Control of challenging behaviour is the primary reason why such medications are prescribed despite the absence of good evidence for any therapeutic effect for this purpose. OBJECTIVES: To assess the feasibility of recruitment and retention and to explore non-efficacy-based barriers to a blinded antipsychotic medication withdrawal programme for adults with LDs without psychosis compared with treatment as usual. A secondary objective was to compare trial arms regarding clinical outcomes. DESIGN: A two-arm individually randomised double-blind placebo-controlled drug reduction trial. SETTING: Recruitment was through community learning disability teams (CLDTs) in south Wales and south-west England. PARTICIPANTS: Adults with LDs who are prescribed risperidone for treatment of challenging behaviour with no known current psychosis or previous recurrence of psychosis following prior drug reduction. INTERVENTION: A double-blind drug reduction programme leading to full withdrawal within 6 months. Treatment in the intervention group was gradually reduced over a 6-month period and then maintained at the same level for a further 3 months, still under blind conditions. In the control group, the baseline level of medication was maintained throughout the 9-month period. The blind was broken at 9 months, following final data collection. MAIN OUTCOME MEASURES: Feasibility outcomes were (1) the number and proportion of general practices/CLDTs that progressed from initial approach to recruitment of participants and (2) the number and proportion of recruited participants who progressed through the various stages of the study. Trial arms were also compared regarding clinical outcomes, the Modified Overt Aggression Scale, the Aberrant Behaviour Checklist, the Psychiatric Assessment Schedule for Adults with Developmental Disability checklist, the Antipsychotic Side-effect Checklist, the Dyskinesia Identification System Condensed User Scale, the Client Service Receipt Inventory, use of other interventions to manage challenging behaviour, use of as-required (pro re nata) medication and level of psychotropic medication use. RESULTS: Of the 22 participants randomised (intervention, n = 11; control, n = 11), 13 (59%) achieved progression through all four stages of reduction. Follow-up data at 6 and 9 months were obtained for 17 participants (intervention, n = 10; and control, n = 7; 77% of those randomised). There were no clinically important changes in participants' levels of aggression or challenging behaviour at the end of the study. There were no expedited safety reports. Four adverse events and one serious adverse event were reported during the trial. LIMITATIONS: Recruitment was challenging, which was largely a result of difficulty in identifying appropriate persons to consent and carer concerns regarding re-emergence of challenging behaviour. Reduced recruitment meant that the full trial became an exploratory pilot study. CONCLUSIONS: The results indicate that drug reduction is possible and safe. However, concerns about taking part were probably exacerbated by limited availability of alternative (behavioural) interventions to manage behaviour; therefore, focused support and alternative interventions are required. The results of the qualitative study provide important insights into the experiences of people taking part in drug reduction studies that should influence future trial development. FUTURE WORK: We recommend that further work focuses on support for practitioners, carers and patients in reducing antipsychotic medication. TRIAL REGISTRATION: Current Controlled Trials ISRCTN38126962. FUNDING: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 21, No. 47. See the NIHR Journals Library website for further project information.
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Antipsicóticos/efeitos adversos , Análise Custo-Benefício , Deficiências da Aprendizagem/psicologia , Adulto , Agressão/psicologia , Antipsicóticos/uso terapêutico , Escalas de Graduação Psiquiátrica Breve , Método Duplo-Cego , Inglaterra , Feminino , Humanos , Masculino , Projetos Piloto , Pesquisa QualitativaRESUMO
BACKGROUND: Randomised controlled trials (RCTs) have a reputation for being inherently difficult to deliver as planned and often face unforeseen challenges and delays, particularly in relation to organisational and governance difficulties, participant interest, constraints due to allocation of costs, local investigator interest and lengthy bureaucracy. Recruitment is often difficult and the challenges faced often impact on the cost and delivery of a successful trial within the funded period. This paper reflects upon the challenges faced in delivering a pragmatic RCT of weight loss maintenance in a community setting and suggests some potential solutions. METHODS: The weight loss maintenance in adults trial aimed to evaluate the impact of a 12 month, individually tailored weight maintenance intervention on BMI 3 years from randomisation. Participants were recruited primarily from participant identification centres (PICs)-GP surgeries, exercise on referral schemes and slimming world. The intervention was delivered in community settings. A recruitment strategy implementation plan was drafted to address and monitor poor recruitment. RESULTS: Delays in opening and recruitment were experienced early on. Some were beyond the control of the study team such as; disagreement over allocation of national health service costs and PIC classification as well as difficulties in securing support from research networks. That the intervention was delivered in community settings was often at the root of these issues. Key items to address at the design stage of future trials include feasibility of eligibility criteria. The most effective element of the recruitment implementation plan was to refocus sources of recruitment and target only those who could fulfil the eligibility criteria immediately. CONCLUSIONS: Learnings from this trial should be kept in mind by those designing similar studies in the future. Considering potential governance, cost and research network support implications at the design stage of pragmatic trials of any community-based complex intervention is paramount. The appropriateness and viability of inclusion criteria also require careful consideration as does use of a targeted advertising strategy. TRIAL REGISTRATION: ISRCTN35774128, 12/01/2010.
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Avaliação de Processos e Resultados em Cuidados de Saúde , Seleção de Pacientes , Ensaios Clínicos Pragmáticos como Assunto/normas , Projetos de Pesquisa/normas , Redução de Peso , Adolescente , Adulto , Idoso , Serviços de Saúde Comunitária , Inglaterra , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Programas Nacionais de Saúde , Adulto JovemRESUMO
BACKGROUND: Obesity has significant health and NHS cost implications. Relatively small reductions in weight have clinically important benefits, but long-term weight loss maintenance (WLM) is challenging. Behaviour change interventions have been identified as key for WLM. Motivation is crucial to supporting behaviour change, and motivational interviewing (MI) has been identified as a successful approach to changing health behaviours. The study was designed as an adequately powered, pragmatic randomised controlled trial (RCT); however, owing to recruitment issues, the study became a feasibility trial. OBJECTIVES: To assess recruitment, retention, feasibility, acceptability, compliance and delivery of a 12-month intervention to support WLM. Secondary objectives were to assess the impact of the intervention on body mass index (BMI) and other secondary outcomes. DESIGN: Three-arm individually randomised controlled trial comprising an intensive arm, a less intensive arm and a control arm. SETTING: Community setting in South Wales and the East Midlands. PARTICIPANTS: Individuals aged 18-70 years with a current or previous BMI of ≥ 30 kg/m(2) who could provide evidence of at least 5% weight loss during the previous 12 months. INTERVENTION: Participants received individually tailored MI, which included planning and self-monitoring. The intensive arm received six face-to-face sessions followed by nine telephone sessions. The less intensive arm received two face-to-face sessions followed by two telephone sessions. The control arm received a leaflet advising them on healthy lifestyle. MAIN OUTCOME MEASURES: Feasibility outcomes included numbers recruited, retention and adherence. The primary effectiveness outcome was BMI at 12 months post randomisation. Secondary outcomes included waist circumference, waist-to-hip ratio, physical activity, proportion maintaining weight loss, diet, quality of life, health service resource usage, binge eating and well-being. A process evaluation assessed intervention delivery, adherence, and participants' and practitioners' views. Economic analysis aimed to assess cost-effectiveness in terms of quality-adjusted life-years (QALYs). RESULTS: A total of 170 participants were randomised. Retention was good (84%) and adherence was excellent (intensive, 83%; less intensive, 91%). The between-group difference in mean BMI indicated the intensive arm had BMIs 1.0 kg/m(2) lower than the controls [95% confidence interval (CI) -2.2 kg/m(2) to 0.2 kg/m(2)]. Similarly, a potential difference was found in weight (average difference of 2.8 kg, 95% CI -6.1 kg to 0.5 kg). The intensive arm had odds of maintaining on average 43% [odds ratio(OR) 1.4, 95% CI 0.6 to 3.5] higher than controls. None of these findings were statistically significant. Further analyses controlling for level of adherence indicated that average BMI was 1.2 kg/m(2) lower in the intensive arm than the control arm (95% CI -2.5 kg/m(2) to 0.0 kg/m(2)). The intensive intervention led to a statistically significant difference in weight (mean -3.7 kg, 95% CI -7.1 kg to -0.3 kg). The other secondary outcomes showed limited evidence of differences between groups. The intervention was delivered as planned, and both practitioners and participants were positive about the intervention and its impact. Although not powered to assess cost-effectiveness, results of this feasibility study suggest that neither intervention as currently delivered is likely to be cost-effective in routine practice. CONCLUSION: This is the first trial of an intervention for WLM in the UK, the intervention is feasible and acceptable, and retention and adherence were high. The main effectiveness outcome showed a promising mean difference in the intensive arm. Owing to the small sample size, we are limited in the conclusions we can draw. However, findings suggest that the intensive intervention may facilitate long-term weight maintenance and, therefore, further testing in an effectiveness trial may be indicated. Research examining WLM is in its infancy, further research is needed to develop our understanding of WLM and to expand theory to inform the development of interventions to be tested in rigorously designed RCTs with cost-effectiveness assessed. TRIAL REGISTRATION: Current Controlled Trials ISRCTN35774128. FUNDING: This project was funded by the National Institute for Health Research Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 19, No. 50. See the NIHR Journals Library website for further project information.
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Terapia Comportamental/métodos , Manutenção do Peso Corporal , Entrevista Motivacional/métodos , Obesidade/terapia , Programas de Redução de Peso/métodos , Adulto , Atitude do Pessoal de Saúde , Terapia Comportamental/economia , Índice de Massa Corporal , Análise Custo-Benefício , Inglaterra , Estudos de Viabilidade , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Entrevista Motivacional/economia , Obesidade/complicações , Obesidade/economia , Avaliação de Processos e Resultados em Cuidados de Saúde/economia , Avaliação de Processos e Resultados em Cuidados de Saúde/métodos , Cooperação do Paciente/estatística & dados numéricos , Satisfação do Paciente , Medicina Estatal/economia , País de Gales , Programas de Redução de Peso/economiaRESUMO
BACKGROUND: Antibiotic prescribing rates in care homes are higher than in the general population. Antibiotics disrupt the normal gut flora, sometimes causing antibiotic-associated diarrhoea (AAD). Clostridium difficile (Hall and O'Toole 1935) Prévot 1938 is the most commonly identified cause of AAD. Little is known either about the frequency or type of antibiotics prescribed in care homes or about the incidence and aetiology of AAD in this setting. OBJECTIVES: The Probiotics for Antibiotic-Associated Diarrhoea (PAAD) study was designed as a two-stage study. PAAD stage 1 aimed to (1) prospectively describe antibiotic prescribing in care homes; (2) determine the incidence of C. difficile carriage and AAD (including C. difficile-associated diarrhoea); and (3) to consider implementation challenges and establish the basis for a sample size estimation for a randomised controlled trial (RCT) of probiotic administration with antibiotics to prevent AAD in care homes. If justified by PAAD stage 1, the RCT would be implemented in PAAD stage 2. However, as a result of new evidence regarding the clinical effectiveness of probiotics on the incidence of AAD, a decision was taken not to proceed with PAAD stage 2. DESIGN: PAAD stage 1 was a prospective observational cohort study in care homes in South Wales with up to 12 months' follow-up for each resident. SETTING: Recruited care homes had management and owner's agreement to participate and three or more staff willing to take responsibility for implementing the study. PARTICIPANTS: Eleven care homes were recruited, but one withdrew before any residents were recruited. A total of 279 care home residents were recruited to the observational study and 19 withdrew, 16 (84%) because of moving to a non-participating care home. MAIN OUTCOME MEASURES: The primary outcomes were the rate of antibiotic prescribing, incidence of AAD, defined as three or more loose stools (type 5-7 on the Bristol Stool Chart) in a 24-hour period, and C. difficile carriage confirmed on stool culture. RESULTS: Stool samples were obtained at study entry from 81% of participating residents. Over half of the samples contained antibiotic-resistant isolates, with Enterobacteriaceae resistant to ciprofloxacin in 47%. Residents were prescribed an average of 2.16 antibiotic prescriptions per year [95% confidence interval (CI) 1.90 to 2.46]. Antibiotics were less likely to be prescribed to residents from dual-registered homes. The incidence of AAD was 0.57 (95% CI 0.41 to 0.81) episodes per year among those residents who were prescribed antibiotics. AAD was more likely in residents who were prescribed co-amoxiclav than other antibiotics and in those residents who routinely used incontinence pads. AAD was less common in residents from residential homes. CONCLUSIONS: Care home residents, particularly in nursing homes, are frequently prescribed antibiotics and often experience AAD. Antibiotic resistance, including ciprofloxacin resistance, is common in Enterobacteriaceae isolated from the stool of care home residents. Co-amoxiclav is associated with greater risk of AAD than other commonly prescribed antibiotics. TRIAL REGISTRATION: Current Controlled Trials ISRCTN 7954844. FUNDING: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 18, No. 63. See the NIHR Journals Library website for further project information.