Multicentre Aneurysm Screening Study (MASS).
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Biomedical subjects
Publications and source records attributed to Tom Marshall.
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BACKGROUND: In 1988, two practices attempted to improve the prescribing of antibiotics for sore throat. The initiative produced only modest improvements in prescribing practice, a finding the authors found difficult to explain. This paper reanalyses the data from an audit of antibiotic prescribing for sore throat in general practice. OBJECTIVE: Our aim was to demonstrate the use of Shewhart control charts and to obtain fresh insight into the variations in clinical practice revealed in clinical audit data. METHODS: We use Shewhart control charts to explore variation in antibiotic prescribing between GPs and to suggest the action most likely to result in improvement. RESULTS: Using control charts, it is possible to distinguish two categories of GPs: low prescribers of antibiotics and high prescribers of antibiotics. Low prescribers of antibiotics show common cause variation, indicating that their prescribing is a stable process. Among low prescribers, improvement can best be achieved by changing the common underlying process. One high prescriber of antibiotics is affected by special cause variation. Among high prescribers, improvement can best be achieved by investigating the special causes affecting this GP and learning lessons from the findings. CONCLUSION: The original improvement effort took the same action on all GPs in both practices. Our analysis suggests that such an approach was unlikely to be successful and that different actions were needed for high and low prescribers. The control charts provide fresh insights on the original data and guide improvement efforts.
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OBJECTIVE: To develop a model to determine resource costs and health benefits of implementing guidelines for the prevention of cardiovascular disease in primary care. DESIGN: Modelling of data from six strategies for prevention of cardiovascular disease. Strategies incorporated two ways of identifying patients for assessment: traditional (assessment of all adults) and novel (preselection of patients for assessment using a prior estimate of their risk of cardiovascular disease). Three treatment strategies were modelled in conjunction with each identification strategy. SETTING: England. SUBJECTS: Patients aged 30 to 74 eligible for primary prevention strategies for cardiovascular disease who were selected from a hypothetical population of 2000. MAIN OUTCOME MEASURES: Resource costs of assessing eligible adults, providing treatment and follow up to those eligible, and number of cardiovascular events this should prevent. RESULTS: Novel strategies prevented more cardiovascular disease, at lower cost, than traditional strategies. Some treatment strategies prevent more cardiovascular disease with fewer resources than others. The findings were robust across a range of different assumptions about workload. CONCLUSION: Preselecting patients for assessment makes better use of staff time than assessing all adults. Treating many patients with low cost drugs is more efficient than prescribing a few patients intensive antihypertensives and statins. Authors of guidelines should model workload implications and health benefits of following their recommendations.
We studied the sex of children born to individuals involved in the Yucheng oil disaster, Taiwan, who were exposed to polychlorinated byphenyls (PCBs) after an oil contamination accident in 1979. Men exposed to PCBs before age 20 years had a lower chance of having a baby boy than did age-matched and neighbourhood-matched controls (odds ratio 0.65, 95% CI 0.45-0.93). The male-to-female sex ratio of children born to men exposed to PCBs after age 20 years, however, approached that seen in controls (0.90, 0.59-1.35). We noted no significant difference in the birth ratio of infants born to exposed and unexposed mothers (0.93, 0.77-1.12). Our findings suggest that paternal exposure to PCBs before age 20 years affects the sex of a subsequently born child.
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BACKGROUND: The aim of clinical governance is to improve clinical care. An understanding of the information contained in variation is central to any improvement effort. We must distinguish between variation intrinsic to a process (common cause variation) and variation caused by extrinsic factors (special cause variation). The control chart is a method of distinguishing between these two kinds of variation: it is used in industry to effect improvement and may be useful in primary care. AIM: To illustrate the use of control charts to distinguish between common cause and special cause variation and to guide appropriate action. DESIGN OF STUDY: Analysis of diagnostic and treatment decisions for sore throat. SETTING: Single practice in the West Midlands. METHODS: We identified each general practitioner's (GP's) consultations for sore throat over a two-year period. We grouped these into two diagnostic categories (tonsillitis and non-tonsillar throat infection) and two treatment categories (antibiotics and no antibiotics). These data were illustrated graphically as XY control charts. RESULTS: In this practice, a special cause affects one GP's diagnosis--he is less likely to use the term 'tonsillitis'. A special cause also affects his treatment decisions--he is more likely to prescribe antibiotics. Diagnostic and treatment differences between the remaining GPs are consistent with common cause variation. CONCLUSION: In this practice, action to improve the quality of diagnosis and treatment of sore throat shouldfocus on investigating why one practitioner's diagnosis and treatment differs from that of his colleagues. Control chart analysis is valuable because it enables users to obtain practical guidance for action.