Health technology assessment : HTA
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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.
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Health Technol Assess · Jan 2000
ReviewFalse-negative results in screening programmes: systematic review of impact and implications.
When assessing whether a screening programme is appropriate, there is a particular obligation to ensure that the harms as well as the benefits are considered. Among these harms is the likelihood that false-negative results will occur. In some cases, the consequences of these can be difficult to assess, although false reassurance leading to diagnostic delay and subsequent treatment has been suggested. However, no test is totally accurate (with 100% sensitivity and specificity), and false-negative results are inherent in any screening programme that does not have 100% sensitivity. This review was carried out to assess the medical, psychological, economic and legal consequences of false-negative results that occur in national screening programmes. ⋯ False-negatives are evident in all screening programmes, even when the quality of the service provided is high. They may have the potential to delay the detection of breast and cervical cancer, but there is little evidence to help assess their psychological consequences in these or other screening programmes. False-negatives are likely to lead to legal action being taken by those individuals affected, and potentially may reduce public confidence in screening. (ABSTRACT TRUNCATED)
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Health Technol Assess · Jan 2000
Randomized Controlled Trial Clinical TrialA randomised controlled trial of prehospital intravenous fluid replacement therapy in serious trauma.
In total 1309 patients were entered in the study: 699 (53.4%) were treated by paramedics operating protocol A and 610 (46.6%) were treated by paramedics operating protocol B. The randomisation worked well and there were no significant differences between treatment groups in incident characteristics, ambulance performance times, or patient or injury characteristics, apart from slightly more moderate or severe head injuries in the protocol A group (25.3% versus 20.3%). Protocol compliance was poor, with only 31% of protocol A patients receiving prehospital fluids and only 80% of protocol B patients not given fluids. The estimated odds ratio for being given prehospital fluids when treated by protocol A compared to protocol B was 2.09 (95% confidence interval (CI), 1.53 to 2.81). ⋯ In the prehospital and immediate-care phase (including A&E treatment), the mean costs of the protocol A and protocol B groups were ¿419 and ¿416, respectively. This small difference reflects two small and offsetting effects of protocol B: reduced on-scene time (p = 0.08) and increased use of blood in the A&E department (p = 0.03). There were no other statistically significant differences in costs, with the mean total costs being ¿2706 and ¿2678 in the protocol A and protocol B groups, respectively (p = 0.52). (ABSTRACT TRUNCA
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Health Technol Assess · Jan 2000
ReviewCoronary artery stents in the treatment of ischaemic heart disease: a rapid and systematic review.
Coronary artery stents are prosthetic linings inserted into coronary arteries via a catheter to widen the artery and increase blood flow to ischaemic heart muscle. They are used in the treatment of ischaemic heart disease (IHD). IHD is a major cause of morbidity and mortality (123,000 deaths per annum) in the UK and a major cost to the NHS. Clinical effects of IHD include subacute manifestations (stable and unstable angina) and acute manifestations (particularly myocardial infarction [MI]). Treatment includes attention to risk factors, drug therapy, percutaneous invasive interventions (PCIs) (including percutaneous transluminal coronary angioplasty [PTCA] and stents) and coronary artery bypass graft surgery (CABG). In the last decade there has been a steady and significant increase in the rate of PCIs for IHD. In the UK, rates per million population increased from 174 in 1991 to 437 in 1998. Stents are now used in about 70% of PCIs. Data from the rest of Europe suggest there is potential for PCI and stent rates to increase considerably. In the UK there is evidence of under-provision and inequity of access to revascularisation procedures. ⋯ For the review of clinical effectiveness, inclusion criteria were: (i) RCT design; (ii) study population comprising adults with IHD in native or graft vessels (including patients with subacute IHD or AMI); (iii) procedure involving elective insertion of coronary artery stents; (iv) elective PTCA (including PTCA with provisional stenting) or CABG as comparator; (v) outcomes defined as one or more of: combined event rate (or event-free survival), death, MI, angina, target vessel revascularisation, CABG, repeat PTCA, angiographic outcomes; (vi) trials that had closed and reported results for all or almost all recruited patients. For the economic evaluation, studies of adults with IHD were included if they were of the following types: studies reporting UK costs; comparative economic evaluation combining both costs and outcomes; economic evaluations reporting costs and outcomes separately for the years 1998 and 1999 (to ensure current practice was included).(ABSTRACT TRUNCATED)