EMElizabeth Mitchell

Elizabeth Mitchell

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Elizabeth Mitchell has a total of 120 co-authors. Here are the top co-authors by number of shared publications:


Latest Publications

  • Open Access

    Identification of SARS-CoV-2 variants of concern in vaccine-breakthrough infections

    by Baha Abdalhamid, Matthew Donahue, Ishrat Kamal-Ahmed, Kyle Strand, Elizabeth Mitchell, Peter C Iwen


  • The future for diagnostic tests of acute kidney injury in critical care: evidence synthesis, care pathway analysis and research prioritisation

    by Peter S Hall, Elizabeth D Mitchell, Alison F Smith, David A Cairns, Michael Messenger, Michelle Hutchinson, Judy Wright, Karen Vinall-Collier, Claire Corps, Patrick Hamilton, et al.

    Background: Acute kidney injury (AKI) is highly prevalent in hospital inpatient populations, leading to significant mortality and morbidity, reduced quality of life and high short- and long-term health-care costs for the NHS. New diagnostic tests may offer an earlier diagnosis or improved care, but evidence of benefit to patients and of value to the NHS is required before national adoption.Objectives: To evaluate the potential for AKI in vitro diagnostic tests to enhance the NHS care of patients admitted to the intensive care unit (ICU) and identify an efficient supporting research strategy.Data sources: We searched ClinicalTrials.gov, The Cochrane Library databases, Embase, Health Management Information Consortium, International Clinical Trials Registry Platform, MEDLINE,metaRegister of Current Controlled Trials, PubMed and Web of Science databases from their inception dates until September 2014 (review 1), November 2015 (review 2) and July 2015 (economic model). Details of databases used for each review and coverage dates are listed in the main report.Review methods: The AKI-Diagnostics project included horizon scanning, systematic reviewing, meta-analysis of sensitivity and specificity, appraisal of analytical validity, care pathway analysis, model-based lifetime economic evaluation from a UK NHS perspective and value of information (VOI) analysis.Results: The horizon-scanning search identified 152 potential tests and biomarkers. Three tests, Nephrocheck®(Astute Medical, Inc., San Diego, CA, USA), NGAL and cystatin C, were subjected to detailed review. The meta-analysis was limited by variable reporting standards, study quality and heterogeneity, but sensitivity was between 0.54 and 0.92 and specificity was between 0.49 and 0.95 depending on the test. A bespoke critical appraisal framework demonstrated that analytical validity was also poorly reported in many instances. In the economic model the incremental cost-effectiveness ratios ranged from £11,476 to £19,324 per quality-adjusted life-year (QALY), with a probability of cost-effectiveness between 48% and 54% when tests were compared with current standard care.Limitations: The major limitation in the evidence on tests was the heterogeneity between studies in the definitions of AKI and the timing of testing.Conclusions: Diagnostic tests for AKI in the ICU offer the potential to improve patient care and add value to the NHS, but cost-effectiveness remains highly uncertain. Further research should focus on the mechanisms by which a new test might change current care processes in the ICU and the subsequent cost and QALY implications. The VOI analysis suggested that further observational research to better define the prevalence of AKI developing in the ICU would be worthwhile. A formal randomised controlled trial of biomarker use linked to a standardised AKI care pathway is necessary to provide definitive evidence on whether or not adoption of tests by the NHS would be of value.Study registration: The systematic review within this study is registered as PROSPERO CRD42014013919.Funding: The National Institute for Health Research Health Technology Assessment programme.


  • Top Cited Papers

    Strategies to improve recruitment to randomised trials

    by Shaun Treweek, Marie Pitkethly, Jonathan Cook, Cynthia Fraser, Elizabeth Mitchell, Frank Sullivan, Catherine Jackson, Tyna K Taskila, Heidi Gardner

    Recruiting participants to trials can be extremely difficult. Identifying strategies that improve trial recruitment would benefit both trialists and health research. To quantify the effects of strategies for improving recruitment of participants to randomised trials. A secondary objective is to assess the evidence for the effect of the research setting (e.g. primary care versus secondary care) on recruitment. We searched the Cochrane Methodology Review Group Specialised Register (CMR) in the Cochrane Library (July 2012, searched 11 February 2015); MEDLINE and MEDLINE In Process (OVID) (1946 to 10 February 2015); Embase (OVID) (1996 to 2015 Week 06); Science Citation Index & Social Science Citation Index (ISI) (2009 to 11 February 2015) and ERIC (EBSCO) (2009 to 11 February 2015). Randomised and quasi-randomised trials of methods to increase recruitment to randomised trials. This includes non-healthcare studies and studies recruiting to hypothetical trials. We excluded studies aiming to increase response rates to questionnaires or trial retention and those evaluating incentives and disincentives for clinicians to recruit participants. We extracted data on: the method evaluated; country in which the study was carried out; nature of the population; nature of the study setting; nature of the study to be recruited into; randomisation or quasi-randomisation method; and numbers and proportions in each intervention group. We used a risk difference to estimate the absolute improvement and the 95% confidence interval (CI) to describe the effect in individual trials. We assessed heterogeneity between trial results. We used GRADE to judge the certainty we had in the evidence coming from each comparison. We identified 68 eligible trials (24 new to this update) with more than 74,000 participants. There were 63 studies involving interventions aimed directly at trial participants, while five evaluated interventions aimed at people recruiting participants. All studies were in health care. We found 72 comparisons, but just three are supported by high-certainty evidence according to GRADE. 1. Open trials rather than blinded, placebo trials. The absolute improvement was 10% (95% CI 7% to 13%). 2. Telephone reminders to people who do not respond to a postal invitation. The absolute improvement was 6% (95% CI 3% to 9%). This result applies to trials that have low underlying recruitment. We are less certain for trials that start out with moderately good recruitment (i.e. over 10%). 3. Using a particular, bespoke, user-testing approach to develop participant information leaflets. This method involved spending a lot of time working with the target population for recruitment to decide on the content, format and appearance of the participant information leaflet. This made little or no difference to recruitment: absolute improvement was 1% (95% CI −1% to 3%). We had moderate-certainty evidence for eight other comparisons; our confidence was reduced for most of these because the results came from a single study. Three of the methods were changes to trial management, three were changes to how potential participants received information, one was aimed at recruiters, and the last was a test of financial incentives. All of these comparisons would benefit from other researchers replicating the evaluation. There were no evaluations in paediatric trials. We had much less confidence in the other 61 comparisons because the studies had design flaws, were single studies, had very uncertain results or were hypothetical (mock) trials rather than real ones. The literature on interventions to improve recruitment to trials has plenty of variety but little depth. Only 3 of 72 comparisons are supported by high-certainty evidence according to GRADE: having an open trial and using telephone reminders to non-responders to postal interventions both increase recruitment; a specialised way of developing participant information leaflets had little or no effect. The methodology research community should improve the evidence base by replicating evaluations of existing strategies, rather than developing and testing new ones.


  • Open Access

    A qualitative study of patients’ feedback about Outpatient Parenteral Antimicrobial Therapy (OPAT) services in Northern England: implications for service improvement

    by Maureen Twiddy, Carolyn J Czoski Murray, Samantha J Mason, David Meads, Judy M Wright, Elizabeth D Mitchell, Jane Minton

    Objective Outpatient parenteral antimicrobial therapy (OPAT) provides opportunities for improved cost savings, but in the UK, implementation is patchy and a variety of service models are in use. The slow uptake in the UK and Europe is due to a number of clinical, financial and logistical issues, including concern about patient safety. The measurement of patient experience data is commonly used to inform commissioning decisions, but these focus on functional aspects of services and fail to examine the relational aspects of care. This qualitative study examines patients’ experiences of OPAT. Design In-depth, semistructured interviews. Setting Purposive sample of OPAT patients recruited from four acute National Health Service (NHS) Trusts in Northern England. These NHS Trusts between them represented both well-established and recently set-up services running nurse at home, hospital outpatient and/or self-administration models. Participants We undertook 28 semistructured interviews and one focus group (n=4). Results Despite good patient outcomes, experiences were coloured by patients' personal situation and material circumstances. Many found looking after themselves at home more difficult than they expected, while others continued to work despite their infection. Expensive car parking, late running services and the inconvenience of waiting in for the nurse to arrive frustrated patients, while efficient services, staffed by nurses with the specialist skills needed to manage intravenous treatment had the opposite effect. Many patients felt a local, general practitioner or community health centre based service would resolve many of the practical difficulties that made OPAT inconvenient. Patients could find OPAT anxiety provoking but this could be ameliorated by staff taking the time to reassure patients and provide tailored information. Conclusion Services configurations must accommodate the diversity of the local population. Poor communication can leave patients lacking the confidence needed to be a competent collaborator in their own care and affect their perceptions of the service.


  • Open Access

    Cost-effectiveness of outpatient parenteral antibiotic therapy: a simulation modelling approach

    by A. Vargas-Palacios, D. M. Meads, M. Twiddy, C. Czoski Murray, C. Hulme, E. D. Mitchell, A. Gregson, P. Stanley, J. Minton

    Objectives: In the UK, patients who require intravenous antimicrobial (IVA) treatment may receive this in the community through outpatient parenteral antimicrobial therapy (OPAT) services. Services include: IVA administration at a hospital outpatient clinic (HO); IVA administration at home by a general nurse (GN) or a specialist nurse (SN); or patient self-administered (SA) IVA administration following training. There is uncertainty regarding which OPAT services represent value for money; this study aimed to estimate their cost-effectiveness. Methods: A cost-effectiveness decision-analytic model was developed using a simulation technique utilizing data from hospital records and a systematic review of the literature. The model estimates cost per QALY gained from the National Health Service (NHS) perspective for short- and long-term treatment of infections and service combinations across these. Results: In short-term treatments, HO was estimated as the most effective (0.7239 QALYs), but at the highest cost (£973). SN was the least costly (£710), producing 0.7228 QALYs. The combination between SN and HO was estimated to produce 0.7235 QALYs at a cost of £841. For long-term treatments, SN was the most effective (0.677 QALYs), costing £2379, while SA was the least costly at £1883, producing 0.666 QALYs. A combination of SA and SN was estimated to produce 0.672 QALYs at a cost of £2128. Conclusions: SN and SA are cost-effective for short- and long-term treatment of infections, while combining services may represent the second-best alternative for OPAT in the UK.


  • Open Access

    Clinical and cost-effectiveness, safety and acceptability of c ommunity i ntra v enous a ntibiotic s ervice models: CIVAS systematic review

    by E D Mitchell, C Czoski Murray, D Meads, J Minton, J Wright, M Twiddy

    Objective Evaluate evidence of the efficacy, safety, acceptability and cost-effectiveness of outpatient parenteral antimicrobial therapy (OPAT) models. Design A systematic review. Data sources MEDLINE, EMBASE, CINAHL, Cochrane Library, National Health Service (NHS) Economic Evaluation Database (EED), Research Papers in Economics (RePEc), Tufts Cost-Effectiveness Analysis (CEA) Registry, Health Business Elite, Health Information Management Consortium (HMIC), Web of Science Proceedings, International Pharmaceutical Abstracts, British Society for Antimicrobial Chemotherapy website. Searches were undertaken from 1993 to 2015. Study selection All studies, except case reports, considering adult patients or practitioners involved in the delivery of OPAT were included. Studies combining outcomes for adults and children or non-intravenous (IV) and IV antibiotic groups were excluded, as were those focused on process of delivery or clinical effectiveness of 1 antibiotic over another. Titles/abstracts were screened by 1 reviewer (20% verified). 2 authors independently screened studies for inclusion. Results 128 studies involving >60 000 OPAT episodes were included. 22 studies (17%) did not indicate the OPAT model used; only 29 involved a comparator (23%). There was little difference in duration of OPAT treatment compared with inpatient therapy, and overall OPAT appeared to produce superior cure/improvement rates. However, when models were considered individually, outpatient delivery appeared to be less effective, and self-administration and specialist nurse delivery more effective. Drug side effects, deaths and hospital readmissions were similar to those for inpatient treatment, but there were more line-related complications. Patient satisfaction was high, with advantages seen in being able to resume daily activities and having greater freedom and control. However, most professionals perceived challenges in providing OPAT. Conclusions There were no systematic differences related to the impact of OPAT on treatment duration or adverse events. However, evidence of its clinical benefit compared with traditional inpatient treatment is lacking, primarily due to the dearth of good quality comparative studies. There was high patient satisfaction with OPAT use but the few studies considering practitioner acceptability highlighted organisational and logistic barriers to its delivery.


  • Open Access

    Community IntraVenous Antibiotic Study (CIVAS): protocol for an evaluation of patient preferences for and cost-effectiveness of community intravenous antibiotic services

    by C Czoski Murray, M Twiddy, D Meads, S Hess, J Wright, E D Mitchell, C Hulme, S Dodd, H Gent, A Gregson, et al.

    Introduction Outpatient parenteral antimicrobial therapy (OPAT) is used to treat a wide range of infections, and is common practice in countries such as the USA and Australia. In the UK, national guidelines (standards of care) for OPAT services have been developed to act as a benchmark for clinical monitoring and quality. However, the availability of OPAT services in the UK is still patchy and until quite recently was available only in specialist centres. Over time, National Health Service (NHS) Trusts have developed OPAT services in response to local needs, which has resulted in different service configurations and models of care. However, there has been no robust examination comparing the cost-effectiveness of each service type, or any systematic examination of patient preferences for services on which to base any business case decision. Methods and analysis The study will use a mixed methods approach, to evaluate patient preferences for and the cost-effectiveness of OPAT service models. The study includes seven NHS Trusts located in four counties. There are five inter-related work packages: a systematic review of the published research on the safety, efficacy and cost-effectiveness of intravenous antibiotic delivery services; a qualitative study to explore existing OPAT services and perceived barriers to future development; an economic model to estimate the comparative value of four different community intravenous antibiotic services; a discrete choice experiment to assess patient preferences for services, and an expert panel to agree which service models may constitute the optimal service model(s) of community intravenous antibiotics delivery. Ethics and dissemination The study has been approved by the NRES Committee, South West—Frenchay using the Proportionate Review Service (ref 13/SW/0060). The results of the study will be disseminated at national and international conferences, and in international journals.


  • Open Access

    Risk factors for emergency presentation with lung and colorectal cancers: a systematic review

    by Elizabeth D Mitchell, Benjamin Pickwell-Smith, Una Macleod

    Objective To identify patient and practitioner factors that influence cancer diagnosis via emergency presentation (EP). Design Systematic review. Data sources MEDLINE, EMBASE, CINAHL, EBM Reviews, Science and Social Sciences Citation Indexes, Conference Proceedings Citation Index-Science and Conference Proceedings Citation Index-Social Science and Humanities. Searches were undertaken from 1996 to 2014. No language restrictions were applied. Study selection Studies of any design assessing factors associated with diagnosis of colorectal or lung cancer via EP, or describing an intervention to impact on EP, were included. Studies involving previously diagnosed cancer patients, assessing only referral pathway effectiveness, outcomes related to diagnosis or post-EP management were excluded. The population was individual or groups of adult patients or primary care practitioners. Two authors independently screened studies for inclusion. Results 22 studies with over 200 000 EPs were included, most providing strong evidence. Five were graded ‘insufficient’, primarily due to missing information rather than methodological weakness. Older patient age was associated with EP for lung and colorectal cancers (OR 1.11–11.03 and 1.19–5.85, respectively). Women were more at risk of EP for lung but not colorectal cancer. Higher deprivation increased the likelihood of lung cancer EP, but evidence for colorectal was less conclusive. Being unmarried (or divorced/widowed) increased the likelihood of EP for colorectal cancer, which was also associated with pain, obstruction and weight loss. Lack of a regular source of primary care, and lower primary care use were positively associated with EP. Only three studies considered practitioner factors, two involving diagnostic tests. No conclusive evidence was found. Conclusions Patient-related factors, such as age, gender and deprivation, increase the likelihood of cancer being diagnosed as the result of an EP, while cancer symptoms and patterns of healthcare utilisation are also relevant. Further work is needed to understand the context in which risk factors for EP exist and influence help-seeking.


  • Top Cited Papers
    Open Access

    Is increased time to diagnosis and treatment in symptomatic cancer associated with poorer outcomes? Systematic review

    by R D Neal, P Tharmanathan, B France, N U Din, S Cotton, J Fallon-Ferguson, W Hamilton, A Hendry, M Hendry, R Lewis, et al.

    Background: It is unclear whether more timely cancer diagnosis brings favourable outcomes, with much of the previous evidence, in some cancers, being equivocal. We set out to determine whether there is an association between time to diagnosis, treatment and clinical outcomes, across all cancers for symptomatic presentations.Methods: Systematic review of the literature and narrative synthesis.Results: We included 177 articles reporting 209 studies. These studies varied in study design, the time intervals assessed and the outcomes reported. Study quality was variable, with a small number of higher-quality studies. Heterogeneity precluded definitive findings. The cancers with more reports of an association between shorter times to diagnosis and more favourable outcomes were breast, colorectal, head and neck, testicular and melanoma.Conclusions: This is the first review encompassing many cancer types, and we have demonstrated those cancers in which more evidence of an association between shorter times to diagnosis and more favourable outcomes exists, and where it is lacking. We believe that it is reasonable to assume that efforts to expedite the diagnosis of symptomatic cancer are likely to have benefits for patients in terms of improved survival, earlier-stage diagnosis and improved quality of life, although these benefits vary between cancers.