Volume 25
Number 3/4
2004

[Table of Contents]

An epidemiologically-based needs assessment for stroke services

Duncan JW Hunter, Heather J Grant, Mark PH Purdue, Robert A Spasoff, John L Dorland and Nam Bains

Abstract

Stroke is amenable to the entire spectrum of health services, ranging from prevention of its risk factors, to the treatment of acute stroke and rehabilitation and palliation of stroke. The aim of this study was to determine the number of persons with the capacity to benefit from evidence-based effective stroke services. Population-based survey and registry data along with published, evidence-based recommendations for services were used to determine the number of persons in Eastern Ontario with stroke (including risk factors, acute stroke and chronic stroke) and their related need for services (including prevention programs, diagnostic services, treatment of acute stroke and rehabilitation). These estimates were then compared to the actual provision of these services. Estimates of the need for effective services exceeded the provision of all services with the exception of pharmacologic treatment for diabetes mellitus and carotid endarterectomy for acute stroke. The approach was able to identify both the under-provision and over-provision of evidence-based effective services for stroke. This study has shown that an epidemiologically-based needs assessment could be a useful basis for the planning of health services.

Key words: needs assessment; provision of health services; stroke

Introduction

How many and what type of health services for stroke ought to be provided at the population level? The answers to these questions depend very much on the 'need' for these services and the way that need is defined. Defining need is problematic because of the many different ways that the term is used. Need has been distinguished in terms of whether it is defined by experts (normative) or by persons with poor health status (felt or expressed) as well as by how it is measured (comparative, demand, and use).^1,2 These distinctions are theoretical and their practical use is debatable. The issue is further muddled by the confusion between a need for health, achieved by broad social improvements, and a need for health services, those interventions traditionally provided by doctors, nurses and other allied health professionals.

In practice, four approaches to assessing the need for health services are used. The first and perhaps the most common use is opinion, and it arises when providers of health services or community representatives are surveyed about their views on the type and amount of services needed. Although these opinions will be informed by experience, they may not be based on any objective measures or upon evidence of effectiveness. While this approach may be the most common way that health needs are identified, it is often criticized for its lack of objectivity and its reliance on the opinion of those who have a vested interest in maintaining a service.

The second way to assess the need for health services is through the use of capitation-based or needs-based funding formulae; this is more accurately a process of resource allocation. Its use arose from observations in the UK that regions with the highest utilization rates were also the poorest, and were receiving fewer health care resources. This resulted in the creation of the Resource Allocation Working Party (RAWP) which was charged with finding more equitable ways of distributing resources to those regions with greater need³ The formulae used typically consist of information on the age and sex composition of the community, and are usually modified by the standardized mortality ratios (SMRs) as a surrogate measure of the healthiness of the population.⁴ Capitated formulae have also been used to allocate other resources, especially to estimate the requirement for physicians.⁵

Third, the need for health services is defined in terms of utilization of health services (e.g., the number of persons discharged from hospital) or awaiting treatment (demand). Utilization in each area may compared to an overall standard or benchmark. The problem with this approach is that the standard may be arbitrary or based on historical patterns of utilization that bear little connection with current reality, i.e., due to the emergence of new treatments and evidence that commonly accepted treatments may be ineffective.⁶ Further, existing patterns of care will identify both inappropriate use by consumers and inappropriate demand induced by providers, neither of which are components of necessary provision.⁷

The final approach has been referred to as 'epidemiologically-based needs assessment' or 'population requirement'.^8,9 The key features are: 1) it is population based; 2) it allows for the incorporation of evidence of effectiveness (systematic reviews, consensus statements, guidelines); and 3) it provides estimates of absolute numbers of required interventions. An intervention may include health promotion, disease prevention, primary care, secondary care, rehabilitation and palliative care. The UK National Health Service has lead the way in this area since its 1991 reforms that emphasized the importance of assessing the health needs of its populations.¹⁰ While estimates of the need have been identified for prostatectomy, primary hip replacement surgery, cataract surgery and radio-therapy for lung cancer, the approach has never been used to estimate the requirement for stroke services.^11-15

Stroke is an important contributor to morbidity and mortality in Canadians. It has been estimated that it is the third leading cause of death in Canada.¹⁰ Further, it is amenable to the entire spectrum of health services, ranging from prevention of its risk factors, to the treatment of acute stroke and rehabilitation and palliation of chronic stroke. Would it be possible to estimate the number of persons in the population at each of these stages and link them with proved effective services?

The aim of this study is to examine the feasibility of carrying out an epidemiologically-based needs assessment in the Canadian context using population health data, using stroke as an example. Specifically, the objectives are: 1) to estimate the number of persons in the population with stroke with the potential to benefit from effective interventions (population requirement); and 2) to determine the number of stroke-related health services provided to individuals to examine whether or not gaps exist between the two.

Methods

A number of population-based data and published, evidence-based recommendations for services were used to determine the number of persons in the population with risk factors for stroke, acute stroke or chronic stroke, along with their related requirement for stroke services (prevention programs, diagnostic services, treatment of acute stroke and rehabilitation). The study population was the 1996 population in Eastern Ontario aged 25 years and older (n = 1,021,910). The population requirement estimates were then compared with provision data taken from routinely collected administrative data. The five main steps were:

• estimating the incidence and prevalence of stroke;
• identifying effective stroke services;
• estimating the population requirement for stroke;
• estimating the provision of services; and
• measuring the gap between requirement and provision.

Each of these steps is described in more detail below.

Estimating the occurrence of stroke

The prevalence of risk factors for stroke was estimated by applying age and sex-specific prevalence estimates for each risk factor to the 1996 population in Eastern Ontario¹⁶ and then summing to estimate the overall frequency of each risk factor. The 1996/97 Ontario Health Survey¹⁷ and the Canadian Heart Health Survey database¹⁸ were used to estimate the prevalence of stroke risk factors, with the exception of atrial fibrillation and transient ischemic attacks, which were taken from other published sources.^19-23

In the absence of Canadian incidence data, the incidence of acute stroke was taken from a stroke registry in Auckland, New Zealand and applied to the Eastern Ontario population.^24-27 Estimates of 7-day and 28-day survival were derived from a number of international registries, covering a total of 7,984 strokes.^28-32

The prevalence of chronic stroke associated with one or more disabilities was taken from the 1990 Ontario Health Survey.³³ These age-sex-specific prevalence estimates were applied to the 1996 Eastern Ontario population to calculate the estimated frequency of chronic stroke cases in the region. The number of stroke cases dying within 1 to 28 days in Eastern Ontario in 1996 was derived by linking discharge data from the Canadian Institute for Health Information and the Registered Persons Database that provides the death date, where applicable, for persons with a valid Ontario health card.³⁵ A summary of the data sources used to measure the prevalence of risk factors, acute stroke and chronic stroke, along with their references, is presented in Table 1.

TABLE 1
Sources of risk factor, acute stroke and chronic stroke prevalence estimates

Identifying recommended stroke services

A list of stroke services was compiled through an extensive literature search of medical and health care journals, and supplemented through consultation with experts recruited from relevant provider and consumer advocacy groups. Additional literature searches of Medline and the Cochrane Library database were undertaken to gather evidence of effectiveness. For this study, an "effective" health service was one for which there exists evidence demonstrating its effectiveness in preventing or treating stroke and/or controlling a stroke-related risk factor. Initial searches identified practice guidelines and consensus statements about services of interest, as these reports provided useful summaries of the overall evidence. A search was also performed to identify systematic reviews or meta-analyses of clinical trials that addressed the effectiveness of each service. Searches that did not yield meta-analyses were repeated, targeting the next highest level of evidence, randomized controlled trials (RCTs). Services not found to have been investigated by RCTs were subjected to a third literature search with no restrictions to study design. The quality of evidence for health service effectiveness was rated using a four-point scale adapted from the U.S. Agency for Health Care and Policy Research.³⁵ Each study was summarized in tables with the following information: 1) non-pharmacologic or pharmacologic; 2) specific type of service; 3) level of evidence, 4) endpoint and 5) treatment effect. In total, 150 different studies were appraised. A summary of the effective interventions, along with the source of the recommendations, is presented in Table 2.

TABLE 2
Source of recommendations for effective stroke-related health services

Estimating the population requirement

Health services aimed at risk factors were classified as either non-pharmacologic, pharmacologic or surgical. Estimates of the use of specific risk factors were identified from the literature and used to determine the proportion of at-risk individuals who could benefit from each type of intervention. The health services targeting the treatment of acute stroke were grouped into three general categories: core stroke services, restricted stroke services, and rehabilitation services (i.e., speech, occupational and physiotherapy). Restricted stroke services were defined as those services that should be provided to only a proportion of acute stroke patients due to reasons of expense, supply, potential adverse events or expected lack of benefit. They include throm-bolytic therapy, brain and vessel imaging tests, carotid endarterectomy and rehabilitation therapy. Prevalence estimates of these indications among stroke cases were then identified from the literature and supplemented by consultation with experts. These were then used to determine the proportion of stroke cases in need of each restricted service.

Estimating the provision of services

The provision of preventive interventions aimed at modifying existing factors was examined. All estimates of pharmacologic intervention for stroke-related risk factors were taken from the 1996 Canadian Disease and Therapeutic Index database, drug treatment data collected quarterly from a sample of 652 office-based Canadian physicians by specialty.³⁶ These data can be used to estimate total treated incidence by diagnosis. Estimates of medication use for diabetes and hypertension were taken from 1996/97 Ontario Health Survey data.³⁷ Information about provision of treatment for hospitalized stroke cases was taken from the Canadian Institute for Health Information hospital database.³⁸ The Ontario Ministry of Health and Long-Term Care Fee-for-service claims database was examined to provide an estimate of the number of stroke cases not hospitalized in Eastern Ontario in 1996.³⁹ The inpatient and same-day surgery databases were used to determine the number of persons in Eastern Ontario in 1996 with a diagnosis of stroke who received either an imaging of the brain, non-invasive imaging of the vessels, or a carotid endarterectomy.⁴⁰

No provincial database maintains information on two of the restricted stroke procedures: conventional cerebral angiography and thrombolytic therapy. Therefore, information for these two therapies was collected from each of four local centres that performed conventional cerebral angiographies in 1996. The number of persons who received recombinant-tissue plasminogen activase (r-tPA) in the first year of its availability was taken from the Canadian Activase for Stroke Effectiveness Study.⁴¹ All the rehabilitation units in Eastern Ontario were surveyed to collect information on rehabilitation therapy for stroke. The Ontario Homecare Administrative Systems Database was employed to determine the number of persons with a stroke-related disability in 1996. This count was determined by the number of persons receiving homecare services who had a primary or secondary diagnosis of stroke.⁴²

Results

Risk factors

An estimated 203,000 persons (19.9% of the population aged 25+) in Eastern Ontario have hypertension, the most important risk factor for stroke; between 23 and 48% of strokes are related to the presence of hypertension. The estimated prevalence of other risk factors for stroke was: low physical activity (397,800), obesity (343,100), smoking (282,500), hyper-cholesterolemia (177,200), ischemic heart disease (55,200), diabetes (41,200), heavy alcohol consumption (35,500), atrial fibrillation (17,800) and transient ischemic attack (13,600). A number of beneficial pharmacologic and non-pharmacologic interventions were identified.

Acute stroke

An estimated 3,525 persons suffered a stroke in 1996. Of these, 3,419 persons surviving immediately after stroke onset required 'core' acute stroke services. These services included: diagnostic tests, prevention of recurrent stroke, prevention of venous thromboembolism, patient/family support, assessment of disability and screening for rehabilitation in hospital. Of the 3,419 immediate survivors, 3,031 were estimated to have required hospitalization and 2,926 survived 28 days after stroke onset. Diagnostic tests required computerized tomography (CT) imaging of the brain (n=3,419), magnetic resonance imaging (MRI) (n=342), and further invasive imaging procedures (n=273). Three hundred and thirty three of the 3,419 stroke survivors would potentially have benefited from r-tPA therapy, while an estimated 137 survivors would have benefited from carotid endarterectomy.

Chronic stroke

It was estimated that 1,846 survivors of acute stroke would require rehabilitation therapy as a result of suffering a stroke in 1996. These therapies were required for the treatment of several conditions including physical immobility, cognitive deficits, communication disorder, swallowing disorders, impaired bladder or bowel function, sleep disturbances and sexual impairments. An estimated 4,312 persons who survived a stroke in 1996 or earlier were estimated to require ongoing assistance performing their activities of daily living.

Comparison of estimated need with provision of services

When these needs were compared to the actual provision of services, there was a slight net over-provision of carotid endarterectomy procedures (137 required versus 196 provided) and a large net over-provision of pharmacologic therapy for diabetes (18,500 required vs. 28,600 provided). There was unmet need for all other health services targeting acute and chronic stroke including r-tPA therapy (333 required versus 52 provided), CT imaging (3,419 required versus 1,006 provided), MRI imaging (342 required versus 145 provided), ultra-sonographic imaging of the vessels (3,419 required versus 432 providedl), radiographic angiographies of the vessels (274 required versus 168 provided) and assistance in performing activities of daily living (4,312 required versus 1,435 provided). Table 3 presents a summary of the gap between the need for stroke services and the actual provision of effective stroke services.

TABLE 3
Population requirement estimates for stroke services, Eastern Ontario, 1996

Discussion

This study found that it was feasible to use population health data to estimate the requirement for health services. Estimates of the population requirement for stroke services exceeded the provision of all services, with the exception of pharmacologic treatment for diabetes mellitus and carotid endarterectomy for acute stroke. The identification of gaps between estimated need and actual provision in local populations may be a useful way to plan the delivery of health services.

Before any conclusions may be drawn, the possible limitations of this study should be identified. These include:

• the application of data from other jurisdictions to local populations;
• the methods used for identification and linkage of effective services with each dimension of stroke;
• the methods used to measure the provision of services;
• the inability to match those who require services with recipients of stoke-related health services; and
• problems with emerging evidence.

Where available, local data were used to estimate the population requirement for services. In some cases (e.g., atrial fibrillation and transient ischemic attacks) local data were unavailable and estimates from outside Canada were applied to local populations. For example, utilization data from Rochester, Minnesota were used to estimate the requirement for acute hospitalization. Given that the proportion of Rochester stroke cases receiving hospitalization (86%) is relatively higher than other reported proportions, we may have overestimated the requirement for hospitalization of stroke services in Eastern Ontario.

Comprehensive lists of health services targeting each stroke-related condition were compiled, and for each health service a summary of the best available evidence of effectiveness was reported. However, for the majority (over 150) of health services identified, too little detail was available to allow evidence of effectiveness of each health service to be described.

In many instances it was difficult to obtain measures of provision of services. This was particularly true for the number of people reached by health promotion programs targeting specific stroke risk factors because it is unknown what proportion of people reached by the promotion actually had the risk factor of interest. Therefore, the estimates we were able to obtain from the public health units regarding the number of persons who were heavy alcohol consumers, infrequent exercisers, and smokers were considered unreliable and excluded from this report. Most estimates of the number of people who received pharmacologic interventions for the various stroke risk factors were taken from the 1996 Canadian Disease Therapeutic Index database. When comparing estimates of need to provision counts, with the exception of diabetes, there is a consistently large apparent underutilization of pharmacologic interventions. The 1996/97 Ontario Health Survey reported counts of medication use much closer to our estimates of need. Strict guidelines have been developed for the use of r-tPA in Canada.⁵⁶ The proportion of acute stroke cases arriving at an emergency care centre within three hours of onset who would qualify to receive r-tPA has not yet been reported in Canada.⁵⁷ Therefore, the model estimate of 333 persons who could potentially benefit from r-tPA may be an overestimate.

FIGURE 1
Percent of need for stroke services that was provided, population requirement, for evidence-based stroke services, Eastern Ontario, 1996

Our estimate of the number of acute stroke survivors receiving rehabilitation therapy was derived from reports from the rehabilitation units in Eastern Ontario. These units supplied data only for those people who received occupational therapy, speech therapy or physiotherapy services. Furthermore, not all rehabilitation units reported statistics for people receiving rehabilitation therapy services on an outpatient basis. Under-reporting of these services would tend to underestimate the number treated.

Although we have estimated the total services needed and received, we have no way of knowing whether the services provided went to the people who needed the services. In other words, there is likely to be a mismatch between need and provision, at the individual level, known as the ecological fallacy. An apparent under-service therefore indicates the net under-service, and thus is the lower limit of the unmet need: to the extent that services were provided to persons who did not need them, the unmet need is actually greater. Similar arguments apply to over-provision of services. A review of the medical records of a sample of persons receiving a certain intervention could determine what proportion of them had the indication for that intervention. By subtraction, this would allow estimation of appropriately provided services, unmet need, and over-provision of services.

A final limitation of this study is the lag period between conducting the literature searches and the emergence of new treatments. For example, intravenous ancrod and endovascular treatment are two acute stroke treatments that are currently being reviewed in the literature, but are not yet in widespread use in Ontario.^50,58-61 The challenge in conducting epidemiologically-based needs assessment lies in keeping up to date with the changing health care environment, while relying on rigorous peer-reviewed published evidence.

In general, estimates of the population requirement for stroke services exceeded the actual provision of these services. Many of the indications for treatments were taken from American sources where the health system is more technology driven, leading to more intensive provision of services. Applying American standards of service provision to Canadian populations could generate requirement estimates that would be considered excessive by Canadian standards. Nevertheless, the results of this study suggest that there is at least some under-provision of stroke services in Eastern Ontario.

A report examining hospital survey results of stroke care in Ontario points to resource allocation and waiting times to receive services as an explanation for under servicing.⁶² This report noted that not all hospitals have equipment such as computed tomography and magnetic resonance imaging scanners necessary to diagnose the cause of acute stroke. The median waiting time for a scan for patients classified as 'urgent' was two hours at hospitals with a CT scanner and 12 hours at hospitals without this technology. The median waiting time for all patients was 12 hours at hospitals with the equipment and 24 hours at hospitals without the equipment.⁶³ The same argument can be made for other procedures such as invasive and non-invasive imaging of blood vessels. If a centre lacks adequate testing facilities and qualified staff to perform procedures, patients who could benefit may not receive required services.

This approach to measuring need represents an improvement in planning health services in a region for two reasons. First, it measures need largely without relying on health service utilization data, which, as a proxy for need, can be biased by supply of services and historical patterns of care. Secondly, it estimates need using recent population characteristics (i.e., 1996 population census data). The precision of such estimates of projected need will be limited by the ability to predict future population changes, as well as any changes in the prevalence of stroke-related conditions.

Future research using the population requirement approach could take several directions. The risk factor frequencies are not independent of one another; it is therefore problematic to add the frequency estimates of different risk factors calculated from this model. For example, the sum of the estimated frequencies of high blood pressure and smoking in Eastern Ontario will not approximate the frequency of individuals in the region who smoke or who are hypertensive. We took the approach of considering the risk factors one at a time. Given the importance of synergistic effects of multiple risk factors, future research is needed to examine the distribution of individuals with multiple risk factors or types of disabilities for purposes of better-informed planning.

This study tested a method to estimate the population requirement and provision of effective stroke services in Eastern Ontario. These results suggest an over-provision of interventions related to diabetes mellitus and carotid endarterectomy, while all other stroke services were under-provided. This study has shown that an epidemiologically-based needs assessment could be a useful tool for planning health services.

Acknowledgements

This project was funded by the Ontario Ministry of Health and Long-Term Care through core funding for the Ontario Health Intelligence Units Program and for the Queen's Centre for Health Services and Policy Research. The views expressed in this article are the authors and do not necessarily reflect the position of the Ontario Ministry of Health and Long-Term Care or of Health Canada.

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Author References

Duncan JW Hunter, John L Dorland, Department of Community Health and Epidemiology, Queen's University, Kingston, Ontario, Canada

Heather J Grant, Mark PH Purdue, Nam Bains, Health Information Partnership, Eastern Ontario Region, Kingston, Ontario, Canada

Robert A Spasoff, Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, Ontario, Canada

Correspondence: Duncan JW Hunter, Department of Community Health and Epidemiology, Abramsky Hall, Queen's University, Kingston, Ontario, Canada K7L 3A6; Fax: (613) 533-6353; E-mail: hunter@post.queensu.ca

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