Evidence-based commissioning: using population impact measures to help primary care trusts estimate the benefit of interventions in diabetes and heart failure.

OBJECTIVE: To test the feasibility of applying population impact measures utilising local population data on established interventions for heart failure and diabetes mellitus. DESIGN: Modelling study. Setting Registered general practitioner (GP) population in a primary care trust (PCT) Data sources Local data sources included the quality and outcomes framework, chronic disease registers for coronary heart disease and diabetes, hospital episode statistics and a range of published risk data in heart failure and diabetes. MAIN OUTCOME MEASURES: Number of events prevented in the population (NEPP) by increasing the uptake of established interventions expressed as the number of deaths, hospitalisations and cardiovascular events prevented. RESULTS: Data from 17 GP practices (representing 55% of the PCT GP registered population) were used to derive the NEPP. A 10% increase in the number of eligible patients receiving ACE inhibitors (n = 191) could result in at least 18 fewer deaths (95% CI 9.8 to 27.1) and 32 fewer hospitalisations (95% CI 24.9 to 40.7) for heart failure every year. Only 45% of persons with diabetes with an above target total cholesterol were receiving a statin; increasing this to 75% (additional 921) could lead to 44 (95% CI 15.6 to 73.1) fewer cardiovascular disease (CVD) events over 5 years. Similarly, more rigorous blood pressure control in an additional 662 diabetic patients could result in 26 (95% CI -2.7 to 55.6) fewer CVD events over 5 years. There were differences in the potential impact of these interventions according to subgroups within the PCT, as defined by age and geography (locality). CONCLUSIONS: Local data and published literature estimates can be successfully combined to produce the number of events prevented within a locally defined PCT population (NEPP). Commissioners have shown interest in the utility of such a measure in identifying and quantifying areas for improvement.

Risk factor measurement quality in primary care routine data was variable but nondifferential between individuals.

OBJECTIVE: To retrospectively assess the quality of cardiovascular disease risk factor measurements in routinely collected data and to examine whether there are systematic differences in measurement quality between individuals of different socioeconomic status, and changes in measurement quality over time. STUDY DESIGN AND SETTING: Comparison of last digit preference in risk factor measurement between a "routine" data set (related to a primary care-based UK cardiovascular risk factor screening programme) and relevant prospective epidemiological surveys (Health Survey for England [HSE] and WHO MONICA). For the routine data set, the records of 37,161 women and 33,977 men aged 35-60 years with a first screening episode during the 11-year period 1989-1999 were analyzed. RESULTS: Last digits of height, weight, and total cholesterol measurements in the routine data set did not exhibit a digit preference pattern, although the degree of random measurement error was greater compared with epidemiological survey data. The last digits of systolic and diastolic blood pressure (BP) measurements exhibited a strong last digit preference pattern for "0"-comprising 63.1% and 67.3% of all observations in men and women, respectively. Except for diastolic BP in men, last digit distribution patterns were not associated with participant's socioeconomic status and showed no change over time. CONCLUSION: It may be feasible to study changes over time in cardiovascular disease risk factor levels in different socioeconomic groups using routine data sets; however, prior critical examination of measurement quality is necessary.

Potential population impact of the UK government strategy for reducing the burden of coronary heart disease in England: comparing primary and secondary prevention strategies.

OBJECTIVE: To use population impact measures to help prioritise the National Service Framework (NSF) strategies recommended by the UK government for reducing the population burden of coronary heart disease (CHD). DESIGN: Modelling study. SETTING: Primary care. DATA SOURCES: Published data on incidence, baseline risk and prevalence of risk factors for CHD and the proportion treated, eligible for treatment, and adhering to the different interventions. Data from meta-analyses and systematic reviews for relative risk and relative risk reduction associated with different risk factors and interventions. MAIN OUTCOME MEASURES: Population impact measures for the decline in the prevalence of a risk factor and the increased uptake of interventions expressed as number of CHD events prevented in the population. RESULTS: If lifestyle targets for primary prevention are met, 73 522 (95% CI 54,117 to 95,826) CHD events would be prevented per year, with the greatest gain coming from reduced cholesterol and blood pressure levels. In those at high risk of developing CHD, achieving target levels for lifestyle interventions would prevent 4410 (95% CI 1993 to 8014) CHD events and for pharmacological treatments 2008 (95% CI 790 to 3627) CHD events. For patients with established CHD, achieving NSF targets will result in the prevention of 3067 (95% CI 1572 to 5878) CHD events through improved drug treatment and 1103 (95% CI 179 to 2097) events through lifestyle interventions. CONCLUSION: Current strategies focus largely on secondary prevention, but many more cardiovascular events would be prevented by meeting the government's public health and primary prevention targets than targeting people at high risk or those with established heart disease.

Deprivation and trends in blood pressure, cholesterol, body mass index and smoking among participants of a UK primary care-based cardiovascular risk factor screening programme: both narrowing and widening in cardiovascular risk factor inequalities.

OBJECTIVES: To examine recent time trends in blood pressure (BP), total cholesterol, body mass index (BMI) and current smoking among people in the UK of different deprivation groups. DESIGN: Repeatable survey. SETTING: Primary care-based UK cardiovascular risk factor screening programme (58 Stockport general practices). PARTICIPANTS: 37,161 women and 33,977 men aged 35-60 years responding to a screening invitation and with a first screening episode during 1989-99. RESULTS: There were significant decreasing trends in total cholesterol (-0.06 mmol/l/year, 95% confidence interval (CI) -0.07 to -0.06 for women, -0.07 mmol/l/year, 95% CI -0.07 to -0.06 for men), with a significantly faster drop in more deprived groups (-0.005 mmol/year/increasing deprivation group, 95% CI -0.01 to -0.001 for both sexes). There were decreasing trends in current smoking prevalence (odds ratio (OR) 0.97/year, 95% CI 0.96 to 0.97 for women, OR 0.96/year, 95% CI 0.95 to 0.96 for men) with a significantly slower drop in the more deprived groups (OR 1.01/year/increasing deprivation group, 95% CI 1.00 to 1.01 for both sexes). There were significant increasing trends in BMI (0.11 kg/m(2)/year in women, 95% CI 0.09 to 0.13, 0.10 kg/m(2)/year in men, 95% CI 0.08 to 0.11), with a significantly slower increase in the more deprived groups among men only (-0.02 kg/m(2)/year/increasing deprivation group, 95% CI -0.01 to -0.03). Inequality in BP narrowed among men but widened among women. CONCLUSION: Inequalities in risk factors between different deprivation groups may be both widening (smoking, BP in women) and narrowing (total cholesterol, BMI and BP in men). Given baseline inequalities in risk factors levels, these trends suggest that inequalities in cardiovascular disease are likely to persist in the future.

Effect of breast feeding on risk of coeliac disease: a systematic review and meta-analysis of observational studies.

BACKGROUND: Coeliac disease (CD) is a disorder that may depend on genetic, immunological, and environmental factors. Recent observational studies suggest that breast feeding may prevent the development of CD. AIM: To evaluate articles that compared effects of breast feeding on risk of CD. METHODS: Systematic review and meta-analysis of observational studies published between 1966 and June 2004 that examined the association between breast feeding and the development of CD. RESULTS: Six case-control studies met the inclusion criteria. With the exception of one small study, all the included studies found an association between increasing duration of breast feeding and decreased risk of developing CD. Meta-analysis showed that the risk of CD was significantly reduced in infants who were breast feeding at the time of gluten introduction (pooled odds ratio 0.48, 95% CI 0.40 to 0.59) compared with infants who were not breast feeding during this period. CONCLUSIONS: Breast feeding may offer protection against the development of CD. Breast feeding during the introduction of dietary gluten, and increasing duration of breast feeding were associated with reduced risk of developing CD. It is, however, not clear from the primary studies whether breast feeding delays the onset of symptoms or provides a permanent protection against the disease. Long term prospective cohort studies are required to investigate further the relation between breast feeding and CD.

Population impact of stricter adherence to recommendations for pharmacological and lifestyle interventions over one year in patients with coronary heart disease.

STUDY OBJECTIVE: To assess the potential number of lives saved associated with the full implementation of aspects of the National Service Framework (NSF) for coronary heart disease (CHD) in England using recently developed population impact measures. DESIGN: Modelling study. SETTING: Primary care. DATA SOURCES: Published data on prevalence of acute myocardial infarction and heart failure, baseline risk of mortality, the relative risk reduction associated with different interventions and the proportion treated, eligible for treatment and adhering to each intervention. MAIN RESULTS: Adopting the NSF recommendations for pharmacological interventions would prevent an extra 1027 (95% CI 418 to 1994) deaths in post-acute myocardial infarction (AMI) patients and an extra 37 899 (95% CI 25 690 to 52 503) deaths in heart failure patients in the first year after diagnosis. Lifestyle based interventions would prevent an extra 848 (95% CI 71 to 1 614) deaths in post-AMI patients and an extra 7249 (95% CI 995 to 16 696) deaths in heart failure patients. CONCLUSIONS: Moving from current to "best" practice as recommended in the NSF will have a much greater impact on one year mortality rates among heart failure patients compared with post-AMI patients. Meeting pharmacological based recommendations for heart failure patients will prevent more deaths than meeting lifestyle based recommendations. Population impact numbers can help communicate the impact on a population of the implementation of guidelines and, when created using local data, could help policy makers assess the local impact of implementing a range of health care targets.

Disease risk and mortality prediction in intensive care patients with pneumonia. Australian and New Zealand practice in intensive care (ANZPIC II).

This study of ventilated patients investigated pneumonia risk factors and outcome predictors in 476 episodes of pneumonia (48% community-acquired pneumonia, 24% hospital-acquired pneumonia, 28% ventilator-associated pneumonia) using a prospective survey in 14 intensive care units within Australia and New Zealand. For community acquired pneumonia, mortality increased with immunosuppression (OR 5.32, CI 95% 1.58-1799, P<0.01), clinical signs of consolidation (OR 2.43, CI 95% 1.09-5.44, P=0.03) and Sepsis-Related Organ Failure Assessment (SOFA) scores (OR 1.19, CI 95% 1.08-1.30, P<0.001) but improved if appropriate antibiotic changes were made within three days of intensive care unit admission (OR 0.42, CI 95% 0.20-0.86, P=0.02). For hospital-acquired pneumonia, immunosuppression (OR 6.98, CI 95% 1.16-42.2, P=0.03) and non-metastatic cancer (OR 3.78, CI 95% 1.20-11.93, P=0.02) were the principal mortality predictors. Alcoholism (OR 7.80, CI 95% 1.20-17.50, P<0.001), high SOFA scores (OR 1.44, CI 95% 1.20-1.75, P=0.001) and the isolation of "high risk" organisms including Pseudomonas aeruginosa, Acinetobacter spp, Stenotrophomonas spp and methicillin resistant Staphylococcus aureus (OR 4.79, CI 95% 1.43-16.03, P=0.01), were associated with increased mortality in ventilator-associated pneumonia. The use of non-invasive ventilation was independently protective against mortality for patients with community-acquired and hospital-acquired pneumonia (OR 0.35, CI 95% 0.18-0.68, P=0.002). Mortality was similar for patients requiring both invasive and non-invasive ventilation and non-invasive ventilation alone (21% compared with 20% respectively, P=0.56). Pneumonia risks and mortality predictors in Australian and New Zealand ICUs vary with pneumonia type. A history of alcoholism is a major risk factor for mortality in ventilator-associated pneumonia, greater in magnitude than the mortality effect of immunosuppression in hospital-acquired pneumonia or community-acquired pneumonia. Non-invasive ventilation is associated with reduced ICU mortality. Clinical signs of consolidation worsen, while rationalising antibiotic therapy within three days of ICU admission improves mortality for community-acquired pneumonia patients.

Survival among hospital in-patients with troponin T elevation below levels defining myocardial infarction.

BACKGROUND: Cardiac troponin T (cTnT) has an accepted place in the management of patients presenting with suspected acute coronary syndrome (ACS). Uncertainty remains about the significance and interpretation of elevated cTnT below the cut-off levels defining myocardial infarction (0.1 microg/l). AIM: To compare the mortality risks for elevation of cTnT in the ranges 0.01-0.029 microg/l, 0.03-0.099 microg/l and <0.01 microg/l. DESIGN: Retrospective record study in three hospitals. METHODS: All cTnT measurements with values in the range >0.01-0.099 microg/l analysed during January 2002 were extracted from clinical biochemistry laboratory databases. Following agreed exclusion criteria, 179 patients with cTnT in the range 0.01-0.099 microg/l and 60 patients <0.01 microg/l were selected at random from across the three sites. Six-month follow-up was completed by review of case notes and contact with the patients' GP. RESULTS: There was a graded increase in mortality with increasing cTnT, although only achieving statistical significance for patients in the 0.03-0.099 microg/l range. The graded increase in relative risk with cTnT was weaker after adjustment for potential confounding factors DISCUSSION: We found a trend for worse survival with increasing cTnT within the range 0.01-0.099 microg/l in unselected patient populations presenting with possible acute coronary syndrome. This suggests that the combined effects of assay imprecision and co-morbidity should be taken into account when interpreting borderline elevation of cTnT. The use of a cut-off based on current standards of assay precision should be used to define the sensitivity of cTnT as biochemical evidence of ischaemic cardiac damage and as an indicator of mortality risk. This level is likely to be between 0.03 and 0.1 microg/l.

Will changes in primary care improve health outcomes? Modelling the impact of financial incentives introduced to improve quality of care in the UK.

OBJECTIVES: To estimate the total health gain from improving the quality of care among patients with cardiovascular disease in line with the quality indicator targets in the new contract for general practitioners (GPs) in the UK. DESIGN: Statistical modelling, applying population impact measures to estimate cardiovascular health gains from achieving treatment targets in the GP contract, taking into account current levels of treatment and control. MAIN OUTCOME MEASURES: Number of events prevented in the population over 5 years applied to a national general practice population of 10,000. RESULTS: The greatest health gain in those aged 45-84 years would come from reaching cholesterol reduction targets. This could prevent 15 events in people with coronary heart disease, seven events in those with a history of stroke, and seven events in those with diabetes. Achieving blood pressure control targets in hypertensive patients without the above conditions could prevent 15 cardiovascular events, with further benefits from reducing blood pressure in patients with high blood pressure and coronary heart disease, stroke, or diabetes. Achieving other targets would have smaller impacts because high levels of care are already being achieved or because of the low prevalence of conditions or associated event risk. CONCLUSION: It is possible to quantify the health gain to a practice population of achieving quality targets such as those set in the new GP contract. The amount of health gain is sensitive to current quality of care, prevalence of conditions, and risk factors, and to the size of change anticipated. Nevertheless, it appears that significant health gains could result from achieving the proposed quality targets.

Early retirement: does cause of invalidity influence rate of social security benefit processing in Zimbabwe?

BACKGROUND: The social security invalidity benefit programme in Zimbabwe is organized through a network of regional offices. There are no standard guidelines for assessing invalidity. Aim We tested whether cause of invalidity and place of residence influenced the rate of processing of invalidity benefit claims. METHOD: We carried out a retrospective cohort study involving 523 medically unadjudicated and a 25% (354/1431) random sample of medically adjudicated invalidity benefit claims at the Central Benefits Office of the National Social Security Authority in Zimbabwe. The outcome for the study was time from certification of invalidity to conclusion of medical adjudication of invalidity benefit claims. RESULTS: Compared with tuberculosis, HIV disease increased the rate of progress to final medical adjudication 2.6-fold, musculoskeletal diseases 1.9-fold, physical injuries 1.7-fold and chronic diseases 1.8-fold after adjusting for place of residence, industrial sector, gender and age. Compared with residing in Harare, residing in Chinhoyi, Gweru, Masvingo and Mutare regions reduced the rate of progress to final medical adjudication by 62, 69, 51 and 56%, respectively, after adjusting for cause of invalidity, industrial sector, gender and age. Compared with invalidity benefit claims from the services sector, those from the mining sector experienced a 45% reduction in rate of progress to final medical adjudication after adjusting for cause of invalidity, place of residence, gender and age. CONCLUSION: Cause of invalidity, place of residence and industrial sector had significant influences on the rate of progress to final medical adjudication of invalidity benefit claims.

Putting the public back into public health. Part I. A re-definition of public health.

The practice of public health has been criticized as being too involved with a narrow, managerial agenda focused on health care rather than the wider horizons of public good. Public accountability is central to the practice of public health, but is not mentioned in current definitions. We offer a new definition that recognizes the centrality of the public, and which should help public health professionals interpret their own role: 'Use of theory, experience and evidence derived through the population sciences to improve the health of the population, in a way that best meets the implicit and explicit needs of the community (the public)'.

Putting the public back into public health. Part II. How can public health be accountable to the public?

The practice of public health involves the application of evidence to improving population health, and should be accountable to the public. Accountability to the public can be considered either at the individual doctor-patient interface or through population-level policy making. The public, at both patient and population levels, should join the professionals at each stage of the 'population health evidence cycle'-in asking for, collecting, understanding and using evidence. A greater appreciation of the non-professional, public perspective would represent a substantial commitment to transforming our understanding and needs for different kinds of evidence required to improve the health of the population.

Impact numbers in health policy decisions.

OBJECTIVE: To outline the major methodological issues appropriate to the use of the population impact number (PIN) and the disease impact number (DIN) in health policy decision making. DESIGN: Review of literature and calculation of PIN and DIN statistics in different settings. SETTING: Previously proposed extensions to the number needed to treat (NNT): the DIN and the PIN, which give a population perspective to this measure. MAIN RESULTS: The PIN and DIN allow us to compare the population impact of different interventions either within the same disease or in different diseases or conditions. The primary studies used for relative risk estimates should have outcomes, time periods and comparison groups that are congruent and relevant to the local setting. These need to be combined with local data on disease rates and population size. Depending on the particular problem, the target may be disease incidence or prevalence and the effects of interest may be either the incremental impact or the total impact of each intervention. For practical application, it will be important to use sensitivity analyses to determine plausible intervals for the impact numbers. CONCLUSIONS: Attention to various methodological issues will permit the DIN and PIN to be used to assist health policy makers assign a population perspective to measures of risk.

Impact numbers: measures of risk factor impact on the whole population from case-control and cohort studies.

OBJECTIVE: To describe new measures of risk from case-control and cohort studies, which are simple to understand and relate to numbers of the population at risk. DESIGN: Theoretical development of new measures of risk. SETTING: Review of literature and previously described measures. MAIN RESULTS: The new measures are: (1) the population impact number (PIN), the number of those in the whole population among whom one case is attributable to the exposure or risk factor (this is equivalent to the reciprocal of the population attributable risk); (2) the case impact number (CIN) the number of people with the disease or outcome for whom one case will be attributable to the exposure or risk factor (this is equivalent to the reciprocal of the population attributable fraction); (3) the exposure impact number (EIN) the number of people with the exposure among whom one excess case is attributable to the exposure (this is equivalent to the reciprocal of the attributable risk); (4) the exposed cases impact number (ECIN) the number of exposed cases among whom one case is attributable to the exposure (this is equivalent to the reciprocal of the aetiological fraction). The impact number reflects the number of people in each population (the whole population, the cases, all those exposed, and the exposed cases) among whom one case is attributable to the particular risk factor. CONCLUSIONS: These new measures should help communicate the impact on a population, of estimates of risk derived from cohort or case-control studies.

A population perspective to evidence based medicine: "evidence for population health".

We explore the notion that the public health community could learn lessons from the success of evidence based medicine (EBM) and develop a public health counterpart called "Evidence for Population Health". While EBM focuses on individual patients, its public health counterpart would aim to improve the health of communities effectively and efficiently.

Knowledge and perception about stroke among an Australian urban population.

BACKGROUND: The aim of the study was to measure knowledge about the symptoms, prevalence and natural history of stroke; the level of concern about having a stroke; understanding of the possibilities for preventing stroke, and the relationship between age, sex, country of origin, educational level, income, self-reported risk factors, and the above factors. METHODS: A random sample of households was selected from an electronic telephone directory in Newcastle and Lake Macquarie area of New South Wales, Australia, between 10 September and 13 October 1999. Within each household the person who was between 18 and 80 years of age and who had the next birthday was eligible to participate in the study (1325 households were eligible). The response rate was 62%. RESULTS: The most common symptoms of stroke listed by respondents were "Sudden difficulty of speaking, understanding or reading" identified by 60.1% of the respondents, and "paralysis on one side of body" identified by 42.0% of the respondents. The level of knowledge of the prevalence of a stroke, full recovery after the stroke, and death from stroke was low and generally overestimated. 69.9% of the respondents considered strokes as being either moderately or totally preventable. There were few predictors of knowledge. CONCLUSION: The study suggests that educational strategies may be required to improve knowledge about a wide range of issues concerning stroke in the community, as a prelude to developing preventive programmes.

Knowledge of stroke risk factors, warning symptoms, and treatment among an Australian urban population.

BACKGROUND AND PURPOSE: Reduction in the risk of stroke and increase in the speed of hospital presentation after the onset of stroke both depend on the level of knowledge of stroke in the general population. The aim of the present study was to assess baseline knowledge regarding stroke risk factors, symptoms, treatment, and information resources. METHODS: A community-based telephone interview survey was conducted in the Newcastle urban area in Australia. A total of 1278 potential participants between the ages of 18 to 80 were selected at random from an electronic telephone directory. A trained telephone interviewer conducted a telephone survey using the Computer-Assisted Telephone Interviewing (CATI) program. RESULTS: A total of 822 participants completed the telephone interview. Six hundred three participants (73.4%) correctly identified the brain as the affected organ in stroke. The most common risk factors for stroke identified by respondents were smoking (identified by 324 [39.4%]) and stress (identified by 277 [33.7%]). The most common warning sign of stroke described by respondents was "blurred and double vision or loss of vision in an eye," listed by 198 (24.1%). A total of 626 (76.2%) respondents correctly listed >/=1 established stroke risk factor, but only 409 (49.8%) respondents correctly listed >/=1 warning sign. CONCLUSIONS: The level of knowledge in the community of established stroke risk factors, warning signs, and treatment as indicated by this survey suggests that a community-based education program to increase public knowledge of stroke may contribute to reducing the risk of stroke and to increasing the speed of hospital presentation after the onset of stroke.

Quality of life: an index for identifying high-risk cardiac patients.

A sample of 945 cardiac patients admitted under emergency conditions completed a quality of life questionnaire 4 months post-discharge. Half (471) were randomly allocated to a group used to develop a logistic regression model to predict mortality and cardiovascular morbidity 8 months later. Age 65-85 years, ever having heart failure, experiencing another cardiovascular event since discharge, and low global quality of life (QOL) score were found to be predictive of these outcomes; an interaction between QOL and heart failure was also found. The model was used to formulate a risk index which was validated in the remaining 474 patients. The index defines four levels of increasing risk of adverse outcomes, with rates in the development and validation groups, respectively, of: low risk 4% and 9%; moderate risk 13% and 15%; high risk 31% and 33%; very high risk 52% and 40%. Scores in the emotional, physical and social QOL domains were also found to be predictive of adverse outcomes, suggesting that interventions in any of these areas may prove beneficial. The index may be useful for follow-up evaluation of cardiac patients.