Health technology assessment : HTA
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Health Technol Assess · Jan 2001
ReviewSubgroup analyses in randomised controlled trials: quantifying the risks of false-positives and false-negatives.
Subgroup analyses are common in randomised controlled trials (RCTs). There are many easily accessible guidelines on the selection and analysis of subgroups but the key messages do not seem to be universally accepted and inappropriate analyses continue to appear in the literature. This has potentially serious implications because erroneous identification of differential subgroup effects may lead to inappropriate provision or withholding of treatment. ⋯ While it is generally recognised that subgroup analyses can produce spurious results, the extent of the problem is almost certainly under-estimated. This is particularly true when subgroup-specific analyses are used. In addition, the increase in sample size required to identify differential subgroup effects may be substantial and the commonly used 'rule of four' may not always be sufficient, especially when interactions are relatively subtle, as is often the case. CONCLUSIONS--RECOMMENDATIONS FOR SUBGROUP ANALYSES AND THEIR INTERPRETATION: (1) Subgroup analyses should, as far as possible, be restricted to those proposed before data collection. Any subgroups chosen after this time should be clearly identified. (2) Trials should ideally be powered with subgroup analyses in mind. However, for modest interactions, this may not be feasible. (3) Subgroup-specific analyses are particularly unreliable and are affected by many factors. Subgroup analyses should always be based on formal tests of interaction although even these should be interpreted with caution. (4) The results from any subgroup analyses should not be over-interpreted. Unless there is strong supporting evidence, they are best viewed as a hypothesis-generation exercise. In particular, one should be wary of evidence suggesting that treatment is effective in one subgroup only. (5) Any apparent lack of differential effect should be regarded with caution unless the study was specifically powered with interactions in mind. CONCLUSIONS--RECOMMENDATIONS FOR RESEARCH: (1) The implications of considering confidence intervals rather than p-values could be considered. (2) The same approach as in this study could be applied to contexts other than RCTs, such as observational studies and meta-analyses. (3) The scenarios used in this study could be examined more comprehensively using other statistical methods, incorporating clustering effects, considering other types of outcome variable and using other approaches, such as Bootstrapping or Bayesian methods.
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Surgical adverse events contribute significantly to postoperative morbidity, yet the measurement and monitoring of events is often imprecise and of uncertain validity. Given the trend of decreasing length of hospital stay and the increase in use of innovative surgical techniques--particularly minimally invasive and endoscopic procedures--accurate measurement and monitoring of adverse events is crucial. ⋯ The use of standardised, valid and reliable definitions is fundamental to the accurate measurement and monitoring of surgical adverse events. This review found inconsistency in the quality of reporting of postoperative adverse events, limiting accurate comparison of rates over time and between institutions. The duration of follow-up for individual events will vary according to their natural history and epidemiology. Although risk-adjusted aggregated rates can act as screening or warning systems for adverse events, attribution of whether events are avoidable or preventable will invariably require further investigation at the level of the individual, unit or department. CONCLUSIONS - RECOMMENDATIONS FOR RESEARCH: (1) A single, standard definition of surgical wound infection is needed so that comparisons over time and between departments and institutions are valid, accurate and useful. Surgeons and other healthcare professionals should consider adopting the 1992 Centers for Disease Control (CDC) definition for superficial incisional, deep incisional and organ/space surgical site infection for hospital monitoring programmes and surgical audits. There is a need for further methodological research into the performance of the CDC definition in the UK setting. (2) There is a need to formally assess the reliability of self-diagnosis of surgical wound infection by patients. (3) There is a need to assess formally the reliability of case ascertainment by infection control staff. (4) Work is needed to create and agree a standard, valid and reliable definition of anastomotic leak which is acceptable to surgeons. (5) A systematic review is needed of the different diagnostic tests for the diagnosis of DVT. (6) The following variables should be considered in any future DVT review: anatomical region (lower limb, upper limb, pelvis); patient presentation (symptomatic, asymptomatic); outcome of diagnostic test (successfully completed, inconclusive, technically inadequate, negative); length of follow-up; cost of test; whether or not serial screening was conducted; and recording of laboratory cut-off values for fibrinogen equivalent units. (7) A critical review is needed of the surgical risk scoring used in monitoring systems. (8) In the absence of automated linkage there is a need to explore the benefits and costs of monitoring in primary care. (9) The growing potential for automated linkage of data from different sources (including primary care, the private sector and death registers) needs to be explored as a means of improving the ascertainment of surgical complications, including death. This linkage needs to be within the terms of data protection, privacy and human rights legislation. (10) A review is needed of the extent of the use and efficiency of routine hospital data versus special collections or voluntary reporting.
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Clinical guidelines, defined as 'systematically developed statements to assist both practitioner and patient decisions in specific circumstances', have become an increasingly familiar part of clinical care. Guidelines are viewed as useful tools for making care more consistent and efficient and for closing the gap between what clinicians do and what scientific evidence supports. Interest in clinical guidelines is international and has its origin in issues faced by most healthcare systems: rising healthcare costs; variations in service delivery with the presumption that at least some of this variation stems from inappropriate care; the intrinsic desire of healthcare professionals to offer, and patients to receive, the best care possible. Within the UK, there is ongoing interest in the development of guidelines and a fast-developing clinical-effectiveness agenda within which guidelines figure prominently. Over the last decade, the methods of developing guidelines have steadily improved, moving from solely consensus methods to methods that take explicit account of relevant evidence. However, UK guidelines have tended to focus on issues of effectiveness and have not explicitly considered broader issues, particularly cost. This report describes the methods developed to handle benefit, harm and cost concepts in clinical guidelines. It reports a series of case studies, each describing the development of a clinical guideline; each case study illustrates different issues in incorporating these different types of evidence. ⋯ The focus of this project was to explore the methods of incorporating cost issues within clinical guidelines. However, the process of reviewing evidence in guideline development groups is becoming increasingly sophisticated, not only in considerations of cost but also in review techniques and group process. At the outset of the project it was unclear how narrowly or broadly the concept of 'cost' could be considered. (ABSTRACT TRUNCATED)
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Health Technol Assess · Jan 2001
ReviewSystematic reviews of wound care management: (5) beds; (6) compression; (7) laser therapy, therapeutic ultrasound, electrotherapy and electromagnetic therapy.
Chronic wounds such as leg ulcers, diabetic foot ulcers and pressure sores are common in both acute and community healthcare settings. The prevention and treatment of these wounds involves many strategies: pressure-relieving beds, mattresses and cushions are universally used as measures for the prevention and treatment of pressure sores; compression therapy in a variety of forms is widely used for venous leg ulcer prevention and treatment; and a whole range of therapies involving laser, ultrasound and electricity is also applied to chronic wounds. This report covers the final three reviews from a series of seven. ⋯ Randomised controlled trials (RCTs) which evaluated these interventions were eligible for inclusion in this review if they used objective measures of outcome such as wound incidence or healing rates. RESULTS - BEDS, MATTRESSES AND CUSHIONS FOR PRESSURE SORE PREVENTION AND TREATMENT: A total of 45 RCTs were identified, of which 40 compared different mattresses, mattress overlays and beds. Only two trials evaluated cushions, one evaluated the use of sheepskins, and two looked at turning beds/kinetic therapy. RESULTS - COMPRESSION FOR LEG ULCERS: A total of 24 trials reporting 26 comparisons were included (two of prevention and 24 of treatment strategies). RESULTS - LOW-LEVEL LASER THERAPY, THERAPEUTIC ULTRASOUND, ELECTROTHERAPY AND ELECTROMAGNETIC THERAPY: Four RCTs of laser (for venous leg ulcers), 10 of therapeutic ultrasound (for pressure sores and venous leg ulcers), 12 of electrotherapy (for ischaemic and diabetic ulcers, and chronic wounds generally) and five of electromagnetic therapy (for venous leg ulcers and pressure sores) were included. Studies were generally small, and of poor methodological quality. CONCLUSIONS (1) Foam alternatives to the standard hospital foam mattress can reduce the incidence of pressure sores in people at risk, as can pressure-relieving overlays on the operating table. One study suggests that air-fluidised therapy may increase pressure sore healing rates. (2) Compression is more effective in healing venous leg ulcers than is no compression, and multi-layered high compression is more effective than single-layer compression. High-compression hosiery was more effective than moderate compression in preventing ulcer recurrence. (3) There is generally insufficient reliable evidence to draw conclusions about the contribution of laser therapy, therapeutic ultrasound, electrotherapy and electromagnetic therapy to chronic wound healing.
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Health Technol Assess · Jan 2001
ReviewClinical and cost-effectiveness of donepezil, rivastigmine and galantamine for Alzheimer's disease: a rapid and systematic review.
Alzheimer's disease is the most common cause of dementia and is characterised by an insidious onset and slow deterioration. The estimated prevalence of Alzheimer's disease for a standard health authority (500,000 people) is about 3330. Current service involves a wide range of agencies, and drug therapy for some patients. ⋯ Studies were included if they fulfilled the following criteria: (1) INTERVENTION: donepezil, rivastigmine or galantamine used to treat Alzheimer's disease. (2) PARTICIPANTS: people diagnosed with Alzheimer's disease who meet the criteria for treatment with donepezil, rivastigmine and galantamine. (3) OUTCOMES: measures assessing changes in cognition, function, behaviour and mood, quality of life (including studies assessing carer well-being and carer-input), and time to institutionalisation. (4) DESIGN: systematic reviews of randomised controlled trials (RCTs) and RCTs comparing donepezil, rivastigmine or galantamine with placebo or each other or non-drug comparators were included in the review of effectiveness. Economic studies of donepezil, rivastigmine or galantamine used to treat Alzheimer's disease that included a comparator (or placebo) and both the costs and consequence (outcomes) of treatment were included in the review of cost-effectiveness. Studies in non-English language, and abstracts and conference poster presentations of systematic reviews, RCTs and economic evaluations were excluded. Two reviewers identified studies by independently screening study titles and abstracts, and then by examining the full text of selected studies to decide inclusion. METHODS - DATA EXTRACTION AND QUALITY ASSESSMENT: Data extraction and quality assessment were undertaken by one reviewer and checked by a second reviewer, with any disagreements resolved through discussion. The quality of RCTs was assessed using the Jadad scale and the quality of systematic reviews was assessed using criteria developed by the NHS Centre for Reviews and Dissemination. The quality of economic evaluation studies was assessed by their internal validity (i.e. the methods used) using a standard checklist, and external validity (i.e. the generalisability of the economic study to the population of interest) using a series of relevant questions. METHODS - DATA SYNTHESIS: The clinical effectiveness and cost-effectiveness of donepezil, rivastigmine and galantamine were synthesised through a narrative review with full tabulation of results of all included studies. In the economic evaluation, the reviewers assessed whether adjustments could be made to existing models to reflect the current situation in England and Wales. RESULTS - CLINICAL EFFECTIVENESS: (1) Donepezil--three systematic reviews and five RCTs (plus four studies from industry (unpublished data, submitted as commercial in confidence)) were found. Results suggest that donepezil is beneficial when assessed using global and cognitive outcome measures. (2) Rivastigmine--three systematic reviews and five RCTs (plus two studies from industry (unpublished data, submitted as commercial in confidence)) were found. Results suggest that rivastigmine is beneficial in terms of global outcome measures. (3) Galantamine--one systematic review and three RCTs (plus three studies from industry (unpublished data, submitted as commercial in confidence)) were found. Results suggest that galantamine is beneficial in terms of global, cognitive and functional scales. RESULTS - SUMMARY OF BENEFITS: It is difficult to quantify benefits from the evidence available in the literature. Statistically significant improvements in tests such as ADAS-cog (Alzheimer's Disease Assessment Scale cognitive subscale) may not be reflected in changes in daily life. (ABSTRACT TRUNCATED)