(Stroke. 2003;34:2502.)
© 2003 American Heart Association, Inc.
Original Contributions |
From the National Stroke Research Institute (H.M.D., A.G.T., G.A.D.) and Neurology Department (H.M.D., R.A.L.M., G.A.D.), Austin & Repatriation Medical Centre, Heidelberg; Department of Medicine, University of Melbourne, Melbourne (H.M.D., R.A.L.M., G.A.D.); Department of Epidemiology and Preventive Medicine, Monash Medical School, Alfred Hospital, Prahran (A.G.T., J.J.M.); and Centre for Health Program Evaluation, Department of Public Health, University of Melbourne, Heidelberg Heights (C.M., R.C.), Australia.
Correspondence to Dr Helen Dewey, National Stroke Research Institute, Level 1, Neurosciences Bldg, Repatriation Campus, Austin & Repatriation Medical Centre, 300 Waterdale Rd, Heidelberg Heights, Victoria 3081, Australia. E-mail helend{at}austin.unimelb.edu au
| Abstract |
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Methods A cost-of-illness model was used to estimate the total first-year costs and lifetime costs of stroke subtypes for all strokes (subarachnoid hemorrhages excluded) that occurred in Australia during 1997. For each subtype, average cost per case during the first year and the present value of average cost per case over a lifetime were calculated. Resource use data obtained in the North East Melbourne Stroke Incidence Study (NEMESIS) were used.
Results The present value of total lifetime costs for all strokes was Aus $1.3 billion (US $985 million). Total lifetime costs were greatest for ischemic stroke (72%; Aus $936.8 million; US $709.7 million), followed by intracerebral hemorrhage (26%; Aus $334.5 million; US $253.4 million) and unclassified stroke (2%; Aus $30 million; US $22.7 million). The average cost per case during the first year was greatest for total anterior circulation infarction (Aus $28 266). Over a lifetime, the present value of average costs was greatest for intracerebral hemorrhage (Aus $73 542), followed by total anterior circulation infarction (Aus $53 020), partial anterior circulation infarction (Aus $50 692), posterior circulation infarction (Aus $37 270), lacunar infarction (Aus $34 470), and unclassified stroke (Aus $12 031).
Conclusions First-year and lifetime costs vary considerably between stroke subtypes. Variation in average length of total hospital stay is the main explanation for differences in first-year costs.
Key Words: Australia costs and cost analysis incidence stroke stroke classification
| Introduction |
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The Oxfordshire Community Stroke Project (OCSP) classification was developed for use in community studies and defines 4 distinct syndromes of ischemic stroke (IS) with consistent patterns of mortality, disability, and risk of recurrence.11 The classification is simple and does not require sophisticated investigations.12 Furthermore, it succinctly describes how patients with IS present to clinicians at the bedside.
The purpose of the present study was to describe the patterns of resource use and to estimate the first-year and lifetime costs for the major stroke subtypes and OCSP subtypes of IS in Australia.
| Methods |
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The main assumption underlying the model was that the incidence rates and resource use data obtained in NEMESIS were representative of the situation in Australia generally. Estimates of the aggregate total cost and average cost per person during the first year after stroke and the estimated present value of the aggregate lifetime costs and average lifetime costs per person for all first-ever-in-a-lifetime strokes that occurred in Australia in 1997 have previously been reported.1 Cost-of-illness models for the lifetime economic costs of subtypes of IS have now been constructed with identical methodology. Incidence and resource use data for these subtypes of IS were obtained from NEMESIS.14 A range of 1-way sensitivity tests have been performed to assess the robustness of the cost estimates.1 This procedure included variation of the discount rate (0%, 3%, and 7%), the costs of hospitalization, and the value of caregiver time. Tests were also performed by substituting the lower and upper bounds of the 95% confidence intervals (CIs) for the proportions of patients resident in a nursing home before stroke, patients hospitalized for acute care, those admitted for inpatient rehabilitation, and patients newly admitted to a nursing home after stroke.
Definitions
Stroke was defined according to the World Health Organization definition of stroke.20 Stroke cases were categorized as IS or ICH on the basis of brain imaging (CT or MRI) or autopsy findings. Cases of stroke that did not undergo brain imaging or autopsy were categorized as unclassified. Cases of IS were subdivided according to the OCSP classification as total anterior circulation infarction (TACI), partial anterior circulation infarction (PACI), posterior circulation infarction (POCI), and lacunar infarction (LACI).11 OCSP subtype was determined on clinical grounds alone without knowledge of specific findings on brain imaging and was based on the symptoms and signs present at the time of maximal deficit after stroke.
Unit Costs
Acute hospitalization costs were determined by use of individual patient-specific costs for the subgroup of stroke patients registered in NEMESIS who were admitted to the Austin & Repatriation Medical Centre (ARMC). These costs were determined from the in-house hospital financial costing system (transition 2) and are untrimmed (ie, patients with particularly long or expensive admissions are not excluded). Stroke patients admitted to hospital for rehabilitation were subclassified according to classes within the Australian National Sub-Acute and Non-Acute Patient Classification (AN-SNAP), a case-mix classification.21 Inpatient rehabilitation costs were determined with the mixed per-diem/per-episode funding model recommended by the authors of the AN-SNAP.21 This method accounts for both the length of stay and relative intensity of resource use for different categories of stroke patients according to age, disability level, and cognitive ability.
Statistical Analysis
Two-tailed t tests were used to compare mean values between groups. Differences in the proportion of first-ever and recurrent cases receiving inpatient rehabilitation and CIs for the differences between these proportions were calculated with the methods outlined by Gardner and Altman22 for calculating CIs for proportions and their differences for unpaired samples.
Ethics
NEMESIS was approved by the ethics committee at each participating institution. Informed consent was obtained before any interview was conducted.
| Results |
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Acute Hospitalization
The proportion of patients admitted to hospital after stroke and the average length of stay varied with stroke subtype (Table 1). The mean length of stay for TACI was approximately twice as long as that for other first-ever stroke subtypes (P=0.006). Unclassified strokes had the shortest length of stay of all first-ever subtypes, although the number of cases was very small and this difference was not statistically significant (P=0.46). Among the subtypes of IS, LACI had the shortest mean length of stay. On average, recurrent stroke cases stayed 1 extra day in hospital compared with first-ever cases, although this difference was not statistically significant (P=0.48).
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The costs of acute hospitalization according to stroke subtype are also shown in Table 1. When untrimmed individual patient-specific costs for the ARMC cohort are used, recurrent cases cost 30% more on average than first-ever-in-a-lifetime cases (an additional Aus $2,000 (US $1515) per admission), although this was not statistically different (P=0.28). Among first-ever cases, TACI had the greatest average cost per admission, and this was more than twice the average for all other cases of first-ever-in-a-lifetime stroke (P=0.004). ICH was the next most expensive, followed by POCI, PACI, and LACI. In contrast, when trimmed average Australian NationalDiagnosis Related Group (AN-DRG) costs (a case-mix payment system) were substituted, ICH cases were the most expensive, and PACI was the least expensive.
Inpatient Rehabilitation
The proportion of first-ever and recurrent 3-month survivors admitted for rehabilitation was similar (45% versus 50%; difference in proportions, -5%; 95%CI, -23 to 13), and there was no significant difference in mean length of inpatient stay for these 2 groups (P=0.95; Table 2). The longest mean lengths of stay occurred for ICH and TACI; however, they were not significantly higher than for the rest of first-ever strokes (P=0.12 for both comparisons).
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The cost of inpatient rehabilitation also varies according to stroke subtype (Table 2). Cases of ICH are most expensive; cases of LACI are least expensive. Furthermore, on average, the cost of rehabilitation for cases of recurrent stroke is greater than for first-ever-in-a-lifetime cases.
Other Resource Use During the First Year After Stroke
Estimated average costs per case for other categories of resource use during the first year after stroke are shown in Table 3. Of note, out-of-pocket costs incurred by stroke cases constituted an important contribution to first-year costs for all stroke subtypes.
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Total First-Year Costs
There are major differences in average first-year costs between the major stroke subtypes. On average, unclassified cases are the least expensive subtype, whereas the costs of ICH are similar to those of IS. There are, however, large differences between the cost per case for subtypes of IS. Cases of TACI are most expensive, followed by PACI, POCI, and LACI. On average, cases of TACI are 1.9 times as expensive as cases of LACI. This is explained primarily by the fact that the costs of acute hospitalization for TACI are more than 3 times those for LACI. These differences disappear to a large degree when the average AN-DRG costs for hospital admissions for stroke (ie, trimmed of outlying values) are substituted. PACI then becomes the most expensive infarct subtype, followed by TACI, POCI, and LACI. Given the clear differences in length of hospital stay between the subtypes of IS among the NEMESIS cohort, the cost estimates shown in Table 3 (incorporating ARMC costs of hospitalization) are likely to be most indicative of the true differences between subtypes.
Total Lifetime Costs
A summary of the present value of average lifetime cost per case and the present value of total lifetime costs for all first-ever-in-a-lifetime stroke in Australia in 1997 according to stroke subtype is presented in Table 4. As for first-year costs, lifetime cost per case varies considerably between subtypes of first-ever-in-a-lifetime stroke. Compared with the situation when only first-year costs are considered, ICH is the most expensive stroke subtype, costing on average 1.7 times the lifetime cost per case of IS.
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With sensitivity testing, the average lifetime costs for ICH range from 1.6 to 2 times the average lifetime costs for IS cases. Among cases of IS, the lifetime cost per case is greatest for TACI, followed by PACI, POCI, and LACI. On an average-cost-per-case basis, LACI costs approximately one third less than TACI. The cost hierarchy for subtypes of IS is largely maintained throughout a range of sensitivity testing. Only 2 scenarios result in another subtype (PACI) being the most expensive infarct subtype over a lifetime: (1) the use of AN-DRG hospital costs, which explicitly exclude cases with very long lengths of stay, and 2) the use of the high point of the 95% CI for the proportion of cases resident in a nursing home at the time of stroke.
| Discussion |
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During the first year after stroke, average costs were similar for IS and ICH cases. However, there were large differences in cost between subtypes of IS. TACI was again the most expensive infarct subtype, costing
1.9 times the cost per case of LACI. The major determinant of these differences was the total cost of hospitalization (acute care and rehabilitation). When AN-DRG trimmed average costs are substituted in the sensitivity analysis, cases of ICH are most expensive. Because the AN-DRG code for any admission is strongly influenced by any surgical procedures, it is likely that the costs of surgery and postoperative care for ICH cases are responsible for the greater costs of this subtype. In contrast, the high costs of hospitalization for TACI reflect the relatively long average length of stay for these patients.
The differences in first-year and lifetime costs seen between the stroke subtypes reflect clear differences in resource use. For TACI, >40% of first-year costs relate to the costs of acute hospitalization, 30% to inpatient rehabilitation, and
6% to nursing home care. Measures that result in a reduced length of acute and rehabilitation hospital stay with no adverse effect on outcome have the potential to realize substantial savings for this subgroup. PACI patients have the highest recurrent stroke costs, so targeted interventions to optimize secondary prevention among this subgroup may result in substantial savings and health gains. Potential strategies, however, need to be assessed through formal economic evaluation.
A note of caution is appropriate with regard to our total cost estimates for stroke subtypes in Australia. These are based on the findings among a cohort of stroke patients residing in inner urban Melbourne, in close proximity to the ARMC, a center for stroke care and research. It is very likely that patterns of care and costs vary considerably across Australia, particularly in nonurban and remote regions. Additional resource use data from other regions of Australia, should they become available, would improve the accuracy of our overall cost estimates for Australia.
At the bedside, clinicians are presented with clinical stroke subtypes with easily recognized characteristics. The patterns of incidence, outcome, and risk of recurrence for the major stroke subtypes and the OCSP subtypes are now well recognized.11,12,14 We have demonstrated that patterns of resource use and costs also vary with stroke subtype. Although other identifiable factors clearly influence stroke costs (eg, age and comorbidities), subtype-specific resource use and cost information is immediately understood by the clinician and healthcare provider. This is the first investigation of the differences in resource use and cost for subtypes of IS beyond the initial period of acute hospitalization. Our findings provide a detailed overview of current stroke care and its costs in Australia and provide input to our economic model, MORUCOS.13 These data provide the necessary starting point (or base case) for future economic evaluations of various aspects of the prevention, treatment, and care of stroke patients. This economic evaluation work is now in progress.
| Acknowledgments |
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Received April 28, 2003; revision received June 16, 2003; accepted June 24, 2003.
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