Health technology assessment : HTA
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Health Technol Assess · Jan 2000
Review Comparative StudyA systematic review of comparisons of effect sizes derived from randomised and non-randomised studies.
There is controversy about the value of evidence about the effectiveness of healthcare interventions from non-randomised study designs. Advocates for quasi-experimental and observational (QEO) studies argue that evidence from randomised controlled trials (RCTs) is often difficult or impossible to obtain, or is inadequate to answer the question of interest. Advocates for RCTs point out that QEO studies are more susceptible to bias and refer to published comparisons that suggest QEO estimates tend to find a greater benefit than RCT estimates. However, comparisons from the literature are often cited selectively, may be unsystematic and may have failed to distinguish between different explanations for any discrepancies observed. ⋯ Relevant literature was identified from: The Cochrane Library, MEDLINE, EMBASE, DARE, and the Science Citation Index. References of relevant papers already identified experts. Electronic searches were very difficult to design and yielded few papers for the first strategy and when identifying study designs. CHOICE OF INTERVENTIONS TO REVIEW FOR STRATEGIES 1 AND 2: For strategy 1, any intervention was eligible. For strategy 2, interventions for which the population, intervention and outcome investigated were anticipated to be homogeneous across studies were selected for review: Mammographic screening (MSBC) of women to reduce mortality from breast cancer. Folic acid supplementation (FAS) to prevent neural tube defects in women trying to conceive. DATA EXTRACTION AND QUALITY ASSESSMENT: Data were extracted by the first author and checked by the second author. Disagreements were negotiated with reference to the paper concerned. For strategy 1, study quality was scored using a checklist to assess whether the RCT and QEO study estimates were derived from the same populations, whether the assessment of outcomes was 'blinded', and the extent to which the QEO study estimate took account of possible confounding. For strategy 2, a more detailed instrument was used to assess study quality on four dimensions: the quality of reporting, the generalisability of the results, and the extent to which estimates of effectiveness may have been subject to bias or confounding. All quality assessments were carried out by three people. DATA SYNTHESIS AND ANALYSIS: For strategy 1, pairs of comparisons between RCT and QEO study estimates were classified as high or low quality. Seven indices of the size of discrepancies between estimates of effect size and outcome frequency were calculated, where possible, for each comparison. Distributions of the size and direction of discrepancies were compared for high- and low-quality comparisons. FOR STRATEGY 2, THREE ANALYSES WERE CARRIED OUT: Attributes of the instrument were described by k statistics, percentage agreement, and Cronbach's a values. Regression analyses were used to investigate -variations in study quality. (ABSTRACT TRUNCATED)
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Health Technol Assess · Jan 2000
ReviewSystematic reviews of wound care management: (3) antimicrobial agents for chronic wounds; (4) diabetic foot ulceration.
Chronic wounds, including pressure sores, leg ulcers, diabetic foot ulcers and other kinds of wounds, healing by secondary intention are common in both acute and community settings. The prevention and treatment of chronic wounds includes many strategies, including the use of various wound dressings, bandages, antimicrobial agents, footwear, physical therapies and educational strategies. This review is one of a series of reviews, and focuses on the prevention and treatment of diabetic foot ulcers and the role of antimicrobial agents in chronic wounds in general. ⋯ The methodological and reporting quality was generally poor. Commonly encountered problems of reporting included lack of clarity about randomisation and outcome measurement procedures, and lack of baseline descriptive data. Common methodological weaknesses included: lack of blinded outcome assessment and lack of adjustment for baseline differences in important variables such as wound size; large loss to follow-up; and no intention-to-treat analysis. RESULTS - PREVENTION OF DIABETIC FOOT ULCERS: There is some evidence (1 large trial) that a screening and foot protection programme reduces the rate of major amputations. The evidence for special footwear (2 small trials) and educational programmes (5 trials) is equivocal. A single trial of podiatric care reported a significantly greater reduction in callus in patients receiving podiatric care. RESULTS - TREATMENT OF DIABETIC FOOT ULCERS: Total contact casting healed significantly more ulcers than did standard treatment in one study. There is evidence from 5 trials of topical growth factors to suggest that these, particularly platelet-derived growth factor, may increase the healing rate of diabetic foot ulcers. Although these studies were of relatively good quality, the sample sizes were far too small to make any definitive conclusions, and growth factors should be compared with current standard treatments in large, multicentre studies. Topical ketanserin increased ulcer healing rate in 2 studies, while systemic hyperbaric oxygen therapy reduced the rate of major amputations in 1 study. Preliminary research into the effects of iloprost and prostaglandin E1 (PGE1) on diabetic foot ulcer healing suggests possible benefits. However, good quality, large-scale confirmatory research is needed. (ABSTRACT TRUNCATED)
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Health Technol Assess · Jan 2000
ReviewIntravascular ultrasound-guided interventions in coronary artery disease: a systematic literature review, with decision-analytic modelling, of outcomes and cost-effectiveness.
Intravascular ultrasound (IVUS) is the generic name for any ultrasound technology used in vivo within the blood vessels. More specifically, intracoronary ultrasound enables imaging of the coronary arteries from within the lumen. This review concentrates on the role of intracoronary ultrasound as an adjunct to interventional cardiology. ⋯ Implications for healthcare: The evidence available is too weak for there to be any reliable implications for clinical practice. (ABSTRACT TRUNCATED)
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Health Technol Assess · Jan 2000
Randomized Controlled Trial Clinical TrialA randomised controlled trial to evaluate the effectiveness and cost-effectiveness of counselling patients with chronic depression.
To examine the effectiveness and cost-effectiveness of short-term counselling in general practice for patients with chronic depression or combined depression and anxiety, compared with general practitioner (GP) care alone. ⋯ Although patients were generally appreciative of the counselling received, there was only limited evidence of improved outcomes in those referred to counselling. Stricter referral criteria to exclude the severely depressed may have yielded more conclusive results. It is also difficult to estimate the effect of recruitment by screening rather than GP referral, which may limit the applicability of the results to routine clinical practice, and may have interfered with the normal working alliance established between the GP, patient and counsellor. A patient preference trial may, therefore, have been more appropriate. The results indicated that there were similar improvements for both CBT and psychodynamic counselling, but a
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Bayesian methods may be defined as the explicit quantitative use of external evidence in the design, monitoring, analysis, interpretation and reporting of a health technology assessment. In outline, the methods involve formal combination through the use of Bayes's theorem of: 1. a prior distribution or belief about the value of a quantity of interest (for example, a treatment effect) based on evidence not derived from the study under analysis, with 2. a summary of the information concerning the same quantity available from the data collected in the study (known as the likelihood), to yield 3. an updated or posterior distribution of the quantity of interest. These methods thus directly address the question of how new evidence should change what we currently believe. They extend naturally into making predictions, synthesising evidence from multiple sources, and designing studies: in addition, if we are willing to quantify the value of different consequences as a 'loss function', Bayesian methods extend into a full decision-theoretic approach to study design, monitoring and eventual policy decision-making. Nonetheless, Bayesian methods are a controversial topic in that they may involve the explicit use of subjective judgements in what is conventionally supposed to be a rigorous scientific exercise. ⋯ Bayesian methods in the health technology assessment context 1. Different contexts may demand different statistical approaches. Prior opinions are most valuable when the assessment forms part of a series of similar studies. A decision-theoretic approach may be appropriate where the consequences of a study are reasonably predictable. 2. The prior distribution is important and not unique, and so a range of options should be examined in a sensitivity analysis. Bayesian methods are best seen as a transformation from initial to final opinion, rather than providing a single 'correct' inference. 3. The use of a prior is based on judgement, and hence a degree of subjectivity cannot be avoided. However, subjective priors tend to show predictable biases, and archetypal priors may be useful for identifying a reasonable range of prior opinion.