Journal of Neurosurgery

May 2012 / Vol. 116 / No. 5 / Pages 1106-1113

Article

Is aggressive treatment of traumatic brain injury cost-effective?
Clinical article

1Departments of Neurosurgery, 2Neurology, and 3Anesthesiology and Critical Care, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania
Abbreviations used in this paper: GCS = Glasgow Coma Scale; GOS = Glasgow Outcome Scale; ICER = incremental cost-effectiveness ratio; ICP = intracranial pressure; QALY = quality-adjusted life year; QOL = quality of life; TBI = traumatic brain injury.
Address correspondence to: Robert G. Whitmore, M.D., Hospital of the University of Pennsylvania, Department of Neurosurgery, 3rd Floor Silverstein, 3400 Spruce Street, Philadelphia, Pennsylvania 19104. email: .

Please include this information when citing this paper: published online March 6, 2012; DOI: 10.3171/2012.1.JNS11962.

Abstract

Object

The object of this study was to determine whether aggressive treatment of severe traumatic brain injury (TBI), including invasive intracranial monitoring and decompressive craniectomy, is cost-effective.

Methods

A decision-analytical model was created to compare costs, outcomes, and cost-effectiveness of 3 strategies for treating a patient with severe TBI. The aggressive-care approach is compared with “routine care,” in which Brain Trauma Foundation guidelines are not followed. A “comfort care” category, in which a single day in the ICU is followed by routine floor care, is included for comparison only. Probabilities of each treatment resulting in various Glasgow Outcome Scale (GOS) scores were obtained from the literature. The GOS scores were converted to quality-adjusted life years (QALYs), based on expected longevity and calculated quality of life associated with each GOS category. Estimated direct (acute and long-term medical care) and indirect (loss of productivity) costs were calculated from the perspective of society. Sensitivity analyses employed a 2D Monte Carlo simulation of 1000 trials, each with 1000 patients. The model was also used to estimate these values for patients 40, 60, and 80 years of age.

Results

For the average 20-year-old, aggressive care yields 11.7 (± 1.6 [SD]) QALYs, compared with routine care (10.0 ± 1.5 QALYs). This difference is highly significant (p < 0.0001). Although the differences in effectiveness between the 2 strategies diminish with advancing age, aggressive care remains significantly better at all ages. When all costs are considered, aggressive care is also significantly less costly than routine care ($1,264,000 ± $118,000 vs $1,361,000 ± $107,000) for the average 20-year-old. Aggressive care remains significantly less costly until age 80, at which age it costs more than routine care. However, even in the 80-year-old, aggressive care is likely the more cost-effective approach. Comfort care is associated with poorer outcomes at all ages and with higher costs for all groups except 80-year-olds.

Conclusions

When all the costs of severe TBI are considered, aggressive treatment is a cost-effective option, even for older patients. Comfort care for severe TBI is associated with poor outcomes and high costs, and should be reserved for situations in which aggressive approaches have failed or testing suggests such treatment is futile.

Severe TBI, defined in patients by a GCS score between 3 and 8, accounts for a significant loss of life and function among young individuals. Studies estimate 1.5 to 2 million people suffer TBI each year in the US, with over 52,000 TBI-related deaths annually.31,40,41 Among those TBI patients who survive, over 200,000 require hospitalization each year (that is, they are readmitted to a hospital), often due to permanent disability.17,29 The economic burden of TBI to society is considerable: in 2000, total costs of TBI, including upfront direct medical costs and loss of productivity, were estimated at $60 billion.14,27 The indirect costs of TBI are expected to increase significantly, in part due to the growing population of TBI patients who survive and require ongoing medical assistance.33

Because the morbidity and mortality associated with TBI are related to both primary and secondary mechanisms,9,30 early and aggressive interventions are associated with improved patient outcomes.4,15,36,42–44,49 Adherence to the Brain Trauma Foundation guidelines has increased significantly among centers19 and has been shown to lead to improvements in functional outcome and mortality rates.4,12,34 In a recent meta-analysis, Stein et al.43 found that invasive treatment (for example, ICP monitoring) of TBI patients was associated with a 12% decrease in mortality rate and a 6% increase in favorable outcomes.

Nevertheless, controversy remains regarding the use of expensive and aggressive treatments for patients with TBI. Harris et al.17 found that the overall mortality rate from TBI was similar between a US hospital and one in the developing nation of Jamaica, despite the availability of advanced technologies and aggressive neurological support in the US. Some retrospective reviews have linked routine ICP monitoring with worse outcomes.1,37 In the pediatric population, some authors have suggested that the reduced mortality from aggressive management of TBI comes at the expense of increased morbidity and costs.23 Similarly, Patel et al.35 argues that the increased mortality observed in patients over the age of 75 years warrants a more conservative approach to treatment. In a recent landmark study, Cooper et al.11 demonstrated that patients with severe TBI and refractory raised ICP who underwent decompressive craniectomy had worse functional outcome than patients who did not receive aggressive therapy.

With the uncertainty surrounding aggressive management of TBI and the high costs of such treatment, it is unclear whether invasive intracranial monitoring and decompressive craniectomy are cost-effective interventions. The purpose of this study is to determine whether aggressive treatment of severe TBI is cost-effective compared with less aggressive–treatment strategies.

Methods

We developed a decision analytical model (Fig. 1) to evaluate costs and outcomes of 3 management strategies for severe TBI, defined here as an admission GCS score of 8 or less and a motor component of 5 or less. The model projects lifetime costs, years of life, and QALYs (defined below). Data for the model were derived from selected published reports and supplemented with original data. Rationales for data choices and details of calculations are included in the Appendix.

Fig. 1. Decision analytical model comparing care strategies for severe TBI.

Treatment Modalities

We included 3 broad approaches to the care of patients with severe TBI: “comfort care,” “routine” care, and aggressive management. In all 3 approaches, we assume identical treatment in the prehospital and initial resuscitation phases. Furthermore, we assumed there were no differences in emergency diagnostic testing and intracranial hematoma evacuation. Care subsequent to hospitalization is also the same in the 3 groups, which differ only with respect to acute hospital management.

The “comfort care” category involves a single day of aggressive care but without invasive intracranial monitoring or decompressive craniectomy, followed by care on a medical-surgical floor. We do not believe there is any call for this approach; it is included only as a comparison group for clinical outcomes and costs. The “routine” care group corresponds to one in which the Brain Trauma Foundation guidelines4 are followed in fewer than 50% of cases.13,43 In contrast, aggressive management is defined as following the guidelines in at least 50% of cases. This includes monitoring ICP until GCS scores rise above 8 or patients follow commands and, for cost purposes, decompressive craniectomy as indicated. Lengths of ICU and hospital stay are based on national norms.13

Clinical Outcomes

Literature reviews were used to provide the percentage of patients in each GOS category at 6 months following treatment. Although there has never been publication of a large series in the comfort-care group, we chose the report of Jennett et al.,22 a large series of cases involving patients from 3 countries at the start of the age of aggressive treatment for severe TBI. While it might be argued that treatment, even at that time, was more aggressive than what is defined by “comfort care,” the case series represent one of the first modern attempts to define injury severity and outcomes. Furthermore, as stated by Jennett et al. at the time of this series publication and later confirmed by others,24,44 mortality rates among severe TBI patients had not declined in decades. Outcomes in the routine-care and aggressive-care groups were obtained from 2 recently published literature reviews comparing the 2 groups.32,43

Long-term QOL was estimated based on 6-month GOS outcomes, which were assumed static for the remainder of life expectancy.10 Final GOS scores were converted to utility, a measure of health-related QOL. We used the conversion formula of Aoki and associates.2 Although there are many scales for QOL, utility is a scale that is parametric, based on subject preference and readily adapted to the needs of cost-effectiveness studies. Multiplying utility during each year by years of life yields QALYs. For example, 1 year of perfect health equals 1 QALY; 2 years in which QOL is only 0.5 also result in 1 QALY. Estimated QALYs were calculated for all 5 GOS categories for each of 4 different age groups (age at time of injury): 20, 40, 60, and 80 years. We used estimates of life expectancy from 2001 US vital statistics3 for patients whose GOS scores were 4 or 5. For patients with GOS scores of 2 or 3 after surgery, we adjusted these life expectancies to reflect GOS-specific mortality rates.7,18,38,45

Costs

All cost estimates were obtained from the literature and corrected to 2011 US dollars.48 Cost elements follow routine practice for cost-effectiveness studies16,26 and consist of medical costs and lost productivity. All costs are considered from the perspective of society. Cost calculations follow the principles outlined by Finkelstein and associates14 in their authoritative work on the economic impact of trauma. Medical costs are based on costs associated with acute hospital care, rehabilitation, and long-term medical expenses. Acute care costs are based primarily on costs associated with the initial hospitalization. For the additional costs associated with ICP monitoring and a proportion of patients who underwent decompressive craniectomies in the aggressive-treatment group, we employed Medicare reimbursement rates as a proxy for costs.8 The incidence of decompressive craniectomy and average length of stay in the aggressive-care unit and the hospital, used in cost calculations in the aggressively treated group, were obtained from a database of prospectively collected data from 1000 consecutive Hospital of the University of Pennsylvania patients with severe TBI and invasive cerebral monitoring. Institutional review board permission was obtained to use this data.

Rehabilitation costs for survivors follow the calculations of Faul and associates' analysis.13 We assumed that the same percentage of members of each GOS group received rehabilitation, regardless of acute treatment. We also assumed that the same percentage in each GOS category are discharged to home or to a nursing home. Longterm medical costs are based primarily on estimated nursing home costs for chronically disabled survivors.14,16 We also considered short-term and long-term loss of productivity (wages, benefits, and housekeeping services), adopting the data of Finkelstein et al.14

Analysis

All QALYs and long-term costs were discounted at 3% per year.16 In our primary analysis we evaluated the optimal management strategy for a patient who was 20 years old at the time of TBI. Our secondary analyses evaluated optimal management strategies for patients aged 40, 60, and 80 years. We calculated the expected years of life saved, expected QALYs saved, expected cost, and expected cost per QALY. We performed sensitivity analysis for each parameter of the model within its 95% confidence interval to determine its relative influence on outcomes and costs. The cost-effectiveness analysis followed routine principles in which treatment strategies were compared using incremental cost-effectiveness ratios.16 If a particular strategy was found to be both more effective and less costly than the alternatives, it was said to dominate the other options, and we did not report a (negative) cost-effectiveness ratio. Sensitivity analysis used beta distributions for probabilities, normal distributions for costs, and a 2D Monte Carlo simulation (expected value for 1000 simulated trials, each made up of 1000 microsimulations). Analyses of the model were performed using TreeAge Pro 2009 (Tree Age Software, Inc.).

Results

Clinical Outcomes

The proportion of patients falling into each GOS category at 6 months after TBI is shown for each treatment modality in Table 1. For each age group studied, comfort care creates fewer QALYs than does routine care, which in turn creates fewer QALYs than does aggressive care. As patient age increases, the differences in QALYs gained diminish. These changes are illustrated in Fig. 2.

Data table

TABLE 1: Proportion of patients in each GOS score category at 6 months after TBI for each treatment strategy*

Fig. 2. Comparison of outcomes for different age groups. yo = years old.

Costs

For each age group studied, aggressive care is associated with the highest acute costs, comfort care the lowest. However, aggressive care is also associated with the lowest mortality rate and the highest rate of good outcomes. Because these outcomes result in lower costs associated with long-term nursing care and lost productivity, the total lifetime costs are lowest in the aggressive-care group and highest in the comfort-care group. Table 2 illustrates all the cost elements for a 20-year-old (a table of these costs for all age groups is available in the Appendix, along with an example of total cost calculation). Relative savings associated with aggressive treatment decrease with advancing age. Average total lifetime costs for all ages are shown in Fig. 3.

Data table

TABLE 2: Costs (in 2011 US dollars) of different treatment strategies in a 20-year-old patient with severe TBI

Fig. 3. Comparison of costs for different age groups. Costs are given in 2011 US dollars.

Cost-Effectiveness

Average effectiveness and costs of each strategy are shown for ages 20, 40, 60, and 80 years in Table 3. For ages 20–60, aggressive care is both more effective and less costly than routine care, which in turn is more effective and less costly than comfort care. Following standard procedure, we compared the cost-effectiveness of 2 strategies by calculating the incremental cost-effectiveness ratio (ICER), the difference in costs divided by the difference in effectiveness.16 In this case, rather than report a negative ICER, we concluded that aggressive care dominates the other 2 strategies. Among 80-year-olds, the difference in costs between aggressive and routine care, divided by the difference in effectiveness, is ($170,978 − $128,432)/(3.2758 − 2.7951) = $88,507 per QALY. In other words, it costs society approximately $88,000 for each QALY gained by employing aggressive care rather than routine care. Whether this can be considered cost-effective depends on society's willingness to pay for improved outcomes. Although the threshold has long been thought to be $50,000 per QALY, recent research suggests a number considerably more than $100,000.5 If one uses this latter threshold, aggressive care can be considered the most cost-effective strategy for all age groups.

Data table

TABLE 3: Comparison of costs and effectiveness of treatment strategies for severe TBI*

Sensitivity Analysis

To allow for uncertainty in our data, we used a Monte Carlo simulation, as outlined in Methods. These results for each age group are shown in the Appendix. For all comparisons between aggressive and routine care, the differences are highly significant (p < 0.0001). The sole exception is cost for a 60-year-old patient, for which p = 0.006.

The advantage of aggressive care over routine care is robust for younger patients. Even the case of the 80-year-old patient bears scrutiny. Figure 4 is a scatterplot of the 3000 simulated trials, showing the mean cost and effectiveness of each trial. Although aggressive care is significantly more expensive than the other 2 strategies, it is also significantly more effective. The graph in Fig. 5, known as an “acceptability” curve, shows the probability that aggressive care is more cost-effective than routine care, based on society's willingness to pay per QALY gained. This shows that aggressive care is likely to be cost-effective, even in an 80-year-old patient.

Fig. 4. Scatterplot of costs and effectiveness of different care levels in an 80-year-old patient. The small dots represent mean values for each of 1000 simulated trials. The large white dots represent the mean values for each care level.

Fig. 5. Acceptability curve for aggressive care in an 80-year-old patient. The x axis represents society's willingness to pay per QALY gained; the y axis is the corresponding probability that aggressive care will be found cost-effective.

Discussion

The results of this analysis clearly indicate that aggressive management of TBI, with invasive ICP monitoring and decompressive hemicraniectomy, is cost-effective across all patient populations, including older patients. This is the first demonstration of the long-term benefits to society of intense upfront treatment of TBI patients. Despite higher initial costs for an aggressive management strategy of TBI, the substantial improvements in patient outcome cause the total lifetime costs to be the lowest of the 3 treatment paradigms.

Although there is scant literature regarding the cost-effectiveness of invasive interventions such as decompressive hemicraniectomy and ICP monitoring in the setting of TBI, the results of extant studies are consistent with our findings. Malmivaara et al.28 performed a cost-effectiveness analysis of 54 cases in which decompressive hemicraniectomy was performed to lower increased ICP after severe TBI. Although mortality was 41% in this patient population at 3 years, survivors' QOL was equal to that of the general population, and the direct cost of neurosurgical treatment for 1 QALY gained was 2400 €. Including indirect costs, the authors estimate a total cost per QALY of 17,900 €, which still qualifies the intervention as cost-effective. Tilford et al.46 studied the cost-effectiveness of aggressive TBI management in the pediatric population and reported estimated ICERs between $38,000 and $115,000 for this treatment strategy. Longer life expectancy was associated with a greater likelihood that aggressive upfront treatment was cost-effective. However, the results of the study are limited by the use of hospital charges rather than actual costs in the analysis.

Our analysis is particularly relevant for institutions or countries with scarce resources. A recent study from Malaysia examined whether it is cost-effective to use multimodal monitoring (such as transcranial Doppler ultrasonography, jugular venous oximetry, and cerebral oxygen monitoring) compared with only ICP monitoring for patients with severe TBI.21 At 1 year, outcomes measured by Barthel Index score were significantly better for TBI patients who underwent multimodal monitoring than those in whom only ICP monitoring was used. Despite the higher initial cost of the multimodal management strategy, it is more cost-effective than using ICP monitoring alone due to its superior outcomes. Although Harris et al.17 reported that the overall mortality rate for TBI patients did not differ between a US hospital with aggressive management strategies and a developing country's hospital without such technology, multivariable analysis of their data showed that patients with severe TBI had a significantly decreased risk of death if treated in the US rather than in the developing country (such as Jamaica). In addition, patients treated at the US hospital showed greater functional improvement than those treated at the Jamaican hospital. A comprehensive cost-effectiveness analysis of this data would likely reveal substantial long-term savings in favor of aggressive management of TBI, as we have reported.

A society's willingness-to-pay threshold determines whether a particular intervention can be deemed cost-effective. The analysis of the oldest TBI patients revealed that it will cost society $88,507 per QALY gained by using the aggressive management strategy compared with routine care. This cost to society is far less than that of many other accepted interventions for older patients. At 2 years' follow-up, a recent study found that surgery for degenerative spondylolisthesis significantly improved health in comparison with nonoperative care, at a cost of $115,600 per QALY gained.47 Similarly, the cost per QALY gained of many chemotherapeutic agents greatly exceeds $100,000.25,39 Because of their shorter life expectancy and the fact that older patients often do not return to work due to retirement rather than disability, economic analyses are skewed toward finding interventions less cost-effective in this population. However, it is likely that current methods of cost analysis may not be sensitive enough to capture the contributions (for example, familial childcare or retirement spending habits) of the older population to society. While outside the scope of this study, aggressive management of TBI in patients older than 80 years may even be cost-effective according to revised estimates of the US willingness-to-pay threshold.5

Cooper et al.11 recently published Class I evidence demonstrating that bifrontotemporoparietal decompressive craniectomy for patients under the age of 60 with severe TBI resulted in worse outcomes at 6 months than standard care according to the Brain Trauma Foundation.6 Although well designed, this surgical trial had an 18% crossover rate for patients in the standard-care group, who underwent the procedure if after 72 hours ICP could not be controlled. In addition, the decompressive-craniectomy group had a significantly greater proportion of patients with bilateral unreactive pupils from brainstem compression. A post hoc covariate adjustment for pupil reactivity showed that the differences in outcome between the 2 groups were no longer significant. Although the results of this study were not included in our analysis, it is unlikely to change our findings. Patients in the craniectomy group had fewer interventions for increased ICP, shorter duration of mechanical ventilation, and fewer days in the ICU, all of which contribute to reducing upfront costs associated with the more aggressive management. A similar trial of decompressive craniectomy, RESCUEicp,20 which employs different entry criteria, surgical timing, and follow-up, is ongoing.

The many assumptions we made and the diverse sources of data contribute to the large variances in our calculations and necessarily detract from the reliability of our conclusions. Faul and associates,13 from whom we obtained much of our data, list several specific limitations of the data on which they base their own calculations. These limitations include an overestimation of the benefits of compliance to the Brain Trauma Foundation guidelines because of very low GCS scores in their sample of patients; an absence of randomized clinical trials in pooling data from published studies on outcomes following TBI; and various assumptions regarding the costs for patients with varying GOS scores.

To these limitations must be added, at the very least, the lack of data on age-specific outcomes in aggressively treated severe TBI patients. Although it is likely that older patients do less well than younger ones, we have had to use the same GOS distributions for all age groups. This renders our cost-effectiveness calculations somewhat optimistic for older patients. Nevertheless, for ages 20–40 years, the dominance of aggressive care over routine care, in terms of both cost and effectiveness, is robust. Even for an average 60- or 80-year-old, the benefits of aggressive care over routine care may be well within the range of society's willingness to pay.5

Conclusions

When all the costs of severe TBI are considered, aggressive treatment is cost-effective, even for older patients. Comfort care for severe TBI is associated with poor outcomes and high costs, and should be reserved for situations in which aggressive approaches have failed or testing suggests such treatment is futile.

Disclosure

This study was funded by the National Institutes of Health's National Institute of Neurological Disorders and Stroke (5T32NS43126-08). The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author contributions to the study and manuscript preparation include the following. Conception and design: Grady, Levine, Stein. Acquisition of data: Grady, Levine, Stein. Analysis and interpretation of data: Whitmore, Stein. Drafting the article: Whitmore, Thawani, Stein. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Whitmore. Statistical analysis: Stein. Administrative/technical/material support: Whitmore, Stein. Study supervision: Grady, Stein.

Appendix

This article contains an appendix that is available only in the online version of the article.

Appendix: Supplementary Data

Outcomes

Life expectancy for Glasgow Outcome Scale (GOS) score categories 4 and 5 were obtained from 2001 US vital statistics.2 We assumed a GOS status of 4 had no adverse effect on life expectancy. Diminished longevities associated with GOS scores of 3 or 2 were calculated according to formulas derived from survival studies of these patients' mortality rates.4,10,11,13 Appendix Table 1 shows the expected years of life for each of the 4 age categories studied. Aoki and associates1 elicited utilities of different GOS states from 140 medical professionals, using the routine gamble approach. Their results are shown in Appendix Table 2. Quality-adjusted life years (QALYs)—and costs—are discounted at 3% per year of life. It is assumed that future rewards and costs are valued less than immediate ones, and routine practice is to discount them at 3% or 5% per year.8 As an example, a 20-year-old can expect to live, on average, 58.12 years. If he or she remains in perfect health (utility = 1), that translates to 28.21 QALYs, with discounting. Appendix Table 3 illustrates the number of expected QALYs associated with a given age and GOS score.

Data table

APPENDIX TABLE 1: Expected years of life after severe TBI for patients in different age and outcome categories*

Data table

APPENDIX TABLE 2: Utility of various GOS states*

Data table

APPENDIX TABLE 3: Expected QALYs after severe TBI

Costs
Lifetime Costs

For patients of a given age category treated with a given treatment strategy, total lifetime costs represent the sum of acute, subacute, and long-term costs specific for those age and treatment categories.

Acute Costs

For purposes of calculating costs, total length of hospital stay is considered the same for the comfort-care and routine-care groups.6 However, we have corrected the estimates of Faul et al.,6 which were based on average costs for all hospitalized traumatic brain injury (TBI) patients, not just for those with severe TBI. We used a formula that relied on the relative cost of a day in the ICU being approximately 3 times as much as care on a medical-surgical floor.9 Hence, in contrast to the calculations of Faul et al., in our calculations, hospitalization for the aggressive-treatment group costs considerably more than that for the routine-care group. Average ICU and hospital stays for the aggressively treated group were obtained from 1000 consecutive patients treated in our Neurocritical Care Unit, and hospital costs were adjusted accordingly. We assumed that all these patients underwent intracranial pressure monitoring and a proportion of them (also calculated from our own experience) underwent decompressive craniectomy. We employed Medicare reimbursement rates as a proxy for costs of these procedures.5 These costs, which are the same for all age groups, are shown in Appendix Table 4.

Data table

APPENDIX TABLE 4: Acute hospital cost calculations*

Subacute Costs

The subacute costs comprise the costs associated with rehabilitation and short-term loss of productivity. According to Faul and associates,6 25% of patients in the GOS score 2–3 category undergo prolonged rehabilitation after hospital discharge. We assumed that this percentage remains constant with age. Correcting their numbers to 2011 levels, rehabilitation costs $16,213.38 for the average patient in the GOS score 2–3 category and $425.58 for the average patient in categories 4 or 5. Faul et al. also summarize the data on short-term productivity for GOS 4 and 5; corrected costs average $4076.24 for patients in this category.

Long-Term Costs

The calculations of costs associated with long-term care vary with longevity and are discounted at 3% per year. They consist of long-term medical costs and productivity costs (lost wages and so forth). For long-term medical costs, Faul et al.6 relied on the calculations of Finkelstein et al.,7 which estimated average long-term medical and nursing home care for all TBI patients. We adjusted this calculation to reflect the greater prevalence of nursing home care for survivors of severe TBI. Our calculation assumes that all patients in a vegetative state are discharged to a nursing home and that enough members of the severe-disability group are also discharged to chronic nursing care so the total equals at least 6.8% of survivors.14 Subtracting the percentage of vegetative patients from this total, we calculated that the percentage of survivors with GOS scores of 3 requiring lifetime nursing care was 15.1% in the comfort-care group, 0.2% in the routine-care group, and 0% in the aggressive-care group. Because Medicaid pays at least 85% of costs for custodial nursing care in the US,15 we used average annual Medicaid payment as a proxy for costs.12 That amounts to $53,393.49/year in 2011 dollars. Total discounted costs for nursing care are shown in Appendix Table 5.

Data table

APPENDIX TABLE 5: Long-term nursing costs (discounted) for survivors of severe TBI

Long-term productivity loss reflects the percentage of patients who cannot return to work, multiplied by the lifetime productivity loss of a disabled patient of different ages. Finkelstein et al.7 provide estimates of both numbers. They estimate that approximately 40% of all patients with severe TBI are unable to return to work within 1 year and that this number is unchanged in Year 4 (we assumed this was permanent). We further assumed that no patients with GOS scores of 3 or less return to work, but all patients with scores of 5 do so. We then calculated the percentage of those with GOS scores of 4 who are permanently disabled, which equals 40% minus the percentage in the GOS score categories 3 and below. These calculations are summarized in Appendix Table 6.

Data table

APPENDIX TABLE 6: Lifetime productivity loss (discounted) for victims of severe TBI

Table 2 in our article (Results section) summarizes cost elements of different treatment strategies in 20-year-old patients. Note that acute hospital costs and intermediate (rehabilitation and short-term productivity) costs are the same for a given GOS score in all age groups. Appendix Table 7 gives the long-term costs for the other age groups we analyzed. Appendix Table 8 summarizes the total costs for each treatment strategy, age, and outcome. The total mean lifetime costs for a given age group and treatment strategy represent a weighted average, based on the costs of a given GOS category, multiplied by the frequency of patients in that category. For example, in the 20-year-old category given comfort care, 22.1% conclude treatment with GOS scores of 5 and their costs average $45,679.37. For GOS 4, the values are 15.9% and $1,108,171.74, and so on. The mean lifetime costs (direct and indirect) for all 20-year-old patients given comfort care is therefore $1,456,059.35.

Data table

APPENDIX TABLE 7: Long-term costs of different treatment strategies in patients with severe TBI

Data table

APPENDIX TABLE 8: Total lifetime costs of different treatment strategies in patients with severe TBI

Cost-Effectiveness Calculations

Appendix Table 9 lists the results of the Monte Carlo simulations for costs and effectiveness for each age group and each care category. It gives means and standard deviations created by the simulations of 1000 trials, each containing 1000 subjects. Note that the mean values calculated in the simulations are slightly different from those calculated using point estimates (Appendix Table 3). This is because the simulations generate random numbers, and their results are slightly different every time they are run.

Data table

APPENDIX TABLE 9: Costs and effectiveness of different strategies for patients of different ages

Two treatments are compared using the incremental cost-effectiveness ratio (ICER), which equals the difference in costs between the two, divided by the difference in effectiveness. If one strategy is both more effective and less costly than another, it is said to dominate. Negative ICERs are not reported. If one treatment is more effective but also more costly than the other, this ratio calculates the cost per unit of additional effectiveness. Units of effectiveness are usually given in QALYs, discussed in the Methods section. Whether a given treatment is cost-effective depends on society's willingness to pay per QALY gained. Traditionally this value is thought to be approximately $50,000–$70,000. However, recent studies suggest the number is considerably larger, perhaps as much as $300,000 per QALY.3

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