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Abstract
Background No randomized controlled trial has successfully compared outcomes between endovascular coiling and microsurgical clipping for unruptured intracranial aneurysms (UIAs).
Objective To perform a cost comparison between index hospitalizations of patients with UIAs treated with coil embolization or surgical clipping to identify the current primary drivers of costs of either management approach.
Methods We obtained index hospitalization costs for 125 cases of UIAs treated with coiling or clipping from 2010 to 2012 at our institution. Comparisons were stratified based on patient age, gender, aneurysm size, and aneurysm location. Using linear regressions, we identified clinical parameters that drive total hospital costs.
Results 69 cases were treated with clipping and 56 cases were treated with coiling. Morbidity and length of stay for patients treated with clipping was higher. Total hospital costs and variable direct costs for clipping were significantly lower than for coiling (p=0.003, p<0.001, respectively). Fixed direct costs and fixed indirect costs for clipping were higher than for coiling (p<0.001, p<0.001, respectively). Variable direct costs comprised 50.5% and 68.6% of total hospital costs for clipping and coiling, respectively (p<0.001). Length of stay, aneurysm size, and patient age drove total hospital costs for clipping. Length of stay was a weak driver of total hospital costs for coiling.
Conclusions Total index hospitalization costs for clipping are lower than for coiling. Costs of clipping and coiling are driven by different clinical variables. The cost of coils and devices is the predominant contributor to the higher total costs of coiling.
- Aneurysm
- Device
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Introduction
Although advancements in diagnostic imaging have yielded better detection of unruptured intracranial aneurysms (UIAs), the ideal treatment of UIAs remains controversial as no randomized controlled trial has successfully compared outcomes between endovascular coiling and microsurgical clipping.1 ,2 Recent studies have investigated the economic impact of each procedure.3–7 However, to our knowledge, no study has conducted a detailed cost analysis of index hospitalizations to demonstrate key drivers of hospital costs.
The goal of our study is to perform a detailed cost comparison between index hospitalizations of patients with UIAs treated with either endovascular coil embolization or surgical clipping. By analyzing hospital costs that have been broken down into discrete cost buckets (such as fixed direct costs, variable direct costs, and fixed indirect costs), we hope to provide a clearer picture of the factors that primarily drive the costs of either management approach. We hypothesize that the total hospital costs accumulated in the initial hospitalization will be higher for clipped patients than those for coiled patients as we anticipate clipped patients to have higher fixed costs from longer lengths of stay and more procedure-related morbidities. However, we also hypothesize that, for patients undergoing coil embolization, the variable costs of endovascular coils and devices will preclude substantial reductions in total costs compared with clipping.
Materials and methods
Financial data
Using Socrates Analytics (Cleveland, Ohio, USA), we obtained detailed breakdowns of index hospitalization costs associated with 125 cases of UIAs treated with either endovascular coil embolization or surgical clipping from 2010 to 2012 at University Hospitals Case Medical Center. The cost analytics software allowed us to exchange patient medical record numbers for fixed direct costs, variable direct costs, and fixed indirect costs associated with each patient's initial hospital stay. These are costs borne by the hospital and not the dollar amounts charged to individual patients or insurance companies.
Fixed direct costs are costs that are directly attributable to clipping or coiling procedures but do not vary based on the number of procedures performed. Examples include the costs of the operating room equipment routinely used for the procedures and the fixed salaries of personnel involved in the procedures and in the follow-up care of the patient. Variable direct costs are costs that are directly attributable to clipping or coiling procedures and vary based on the number of procedures performed. Examples include the costs of the aneurysm coil or clip and the costs of pharmaceuticals required for either procedure. Fixed indirect costs are costs that cannot be directly assigned to clipping or coiling procedures but are still charged in relation to the procedures. Examples include administrative costs and the costs associated with usage and maintenance of the operating room or angiography suite, such as electricity or water. Total hospital cost is defined as the sum of the fixed direct costs, variable direct costs, and fixed indirect costs.
Patients
We obtained patient demographics and aneurysm characteristics from our clinical database. To perform stratified cost comparisons we retrieved patient age, patient gender, length of stay, aneurysm size, and aneurysm location. We excluded patients with underlying diagnoses of subarachnoid hemorrhage who underwent management of remaining UIAs. For the sake of cost accuracy and due to limitations of Socrates Analytics, we excluded patients who underwent management of more than one aneurysm in a given day.
To compare clinical outcomes we surveyed hospital discharge documents for in-hospital mortality and procedure-related morbidities such as discharge to rehabilitation or skilled nursing facilities, transient or permanent neurologic deficits, MRI evidence of substantial ischemic injury, and perioperative infections.
Statistical analysis
We compared the means of continuous variables and the percentages of categorical variables in our data. The Mann–Whitney U test and the Student t test were used to assess the significance of differences between continuous variables. The χ2 test was used to assess the significance of differences between categorical variables. We used two-sided tests and accepted statistical significance at p values <0.05.
Results
Patient demographics
Of the 125 cases we identified, 69 (55.2%) were treated with surgical clipping and 56 (44.8%) were treated with coil embolization (table 1). Both groups of patients were predominantly female (75.4% and 77.6%, respectively). The average patient age was higher in the group treated with coiled embolization (57.6 vs 52.2, p<0.05). The percentage of cases with aneurysms in the posterior circulation was comparable between the patients treating with clipping and those treated with coiling (36.3% and 35.6%, respectively), and the aneurysm sizes between clipped and coiled patients were not significantly different (8.22 mm and 7.57 mm, respectively).
Patient and aneurysm characteristics
Patient outcomes
The average length of stay for patients who underwent microsurgical clipping was longer than for patients who underwent endovascular embolization (4.10 days vs 2.16 days, p<0.001). The median length of stay for patients who underwent microsurgical clipping and endovascular embolization was 3 days and 1 day, respectively. The procedure-related morbidity was higher in patients treated with clipping than in those treated with coiling but did not reach statistical significance (18.8% vs 10.7%, p=0.17). In our group of patients who underwent clipping, nine patients were discharged to acute rehabilitation or skilled nursing facilities (two for postoperative confusion, one for postoperative seizures, and six for focal residual neurological deficits), two experienced postoperative stroke, and six experienced cranial nerve deficits, four of which were transient. In our group of patients treated with coiling, six patients had morbidity: three went to skilled nursing (one each with stroke, transient contrast-induced encephalopathy and grand mal seizure plus other comorbidities), one had a stroke but was discharged home, one had an intraprocedural rupture but was discharged home, and one had transient cranial nerve palsy. At the time of discharge, 9 of 69 patients in the clipping group and 6 of 53 patients in the coiling group had a modified Rankin Scale score of ≥3 (13% vs 11.3%, p=0.61). At 2-month follow-up, 3 of 69 patients treated with clipping and 0 of 53 patients who underwent coiling had a modified Rankin Scale score of ≥3 (4.3% vs 0%, p=0.12).
Cost comparisons
Total hospital costs for clipping (mean $24 574) were significantly lower than total hospital costs for coiling (mean $31 371, p=0.003; table 2). This relationship remained statistically significant in patients aged <60 years, in those with anterior circulation aneurysms, in patients with aneurysms >7 mm, and in female patients (table 2).
Cost comparisons and stratified analysis
Fixed direct costs for patients undergoing clipping (mean $4654) were significantly higher than fixed direct costs for those undergoing coiling (mean $3699, p<0.001). This relationship retained statistical significance in patients aged >60 years, those aged ≤60 years, patients with posterior circulation aneurysms, patients with anterior circulation aneurysms, those with aneurysms <7 mm, those with aneurysms ≥7 mm, and in female patients (table 2).
Fixed indirect costs for clipped patients (mean $7880) were significantly higher than fixed indirect costs for coiled patients (mean $5258, p<0.001). This relationship held significance in patients aged >60 years, those aged ≤60 years, patients with posterior circulation aneurysms, patients with anterior circulation aneurysms, those with small aneurysms, those with large aneurysms, female and male patients (table 2).
Variable direct costs for clipping (mean $12 386) were significantly lower than variable direct costs for coiling (mean $22 594, p<0.001). This relationship held significance in patients aged >60 years, those aged ≤60 years, patients with posterior circulation aneurysms, patients with anterior circulation aneurysms, those with small aneurysms, those with large aneurysms, and in female patients (table 2).
The average proportions of total hospital costs accounted for by variable direct costs for clipping and coiling were 50.5% and 68.6%, respectively (p<0.001), and held significance across all categories of stratification. Average length of stay for clipping was longer than for coiling (p<0.001) and remained significant when stratifying for patient age (p<0.001), gender (p=0.004), posterior aneurysms (p<0.001), and aneurysm size (p<0.001).
We also independently compared the costs of both clipping and coiling between different age groups, patient gender, aneurysm sizes, and aneurysm locations. Among clipped patients, the difference in length of stay between patients aged >60 years and those aged <60 years approached significance (4.86 days vs 3.91 days, p=0.17), but total hospital costs were not significantly different ($25 367 vs $24 372, p=0.68). Among patients who underwent coiling, neither length of stay nor total hospital costs differed significantly between older and younger patients; gender did not significantly alter length of stay or total hospital costs. Among patients treated with surgical clipping, patients with large aneurysms had longer lengths of stay than those with small aneurysms (4.74 days vs 3.58 days, p=0.03), and patients with large aneurysms also had higher total hospital costs than those with small aneurysms ($27 542 vs $22 153, p=0.003). Among patients treated with coiling, those with large aneurysms also had higher total hospital costs than patients with small aneurysms ($36 452 vs $26 640, p=0.02). For both groups of patients, aneurysm position in the anterior or posterior circulation did not significantly alter lengths of stay or total hospital costs.
Linear regressions
Our multivariate linear regression results demonstrate that, for surgical clipping, patient length of stay (p<0.001), aneurysm size (p=0.01), and patient age (p=0.02) were significant contributors to total hospital costs (adjusted R2=0.77, p<0.001; table 3). For coil embolization, only length of stay (p=0.03) was a significant contributor to total hospital costs. However, compared with our cost model for surgical clipping, the cost model for coil embolization has poor explanatory power (adjusted R2=0.02, p=0.29).
Linear regression coefficients of total hospital costs
Discussion
While much work has been done to elucidate the natural history and to quantify the rupture risks of UIAs, balancing the risks of treatment with the progression of the disease remains a challenge for neurointerventionalists and neurosurgeons.1 ,2 ,8–13 To date, a randomized trial involving patients with UIAs that allows for robust comparisons of the outcomes of endovascular and surgical approaches has not been successfully completed. Numerous studies in the past have retrospectively examined or systematically reviewed the clinical outcomes of patients with UIAs who were treated with endovascular or surgical interventions.8 ,14–18 However, until recently, relatively few studies have investigated the economic impact of the treatment modalities of UIAs.3–7
Andaluz and colleagues performed an analysis of trends in the treatment of cerebral aneurysms from 1993 to 2003 using the Nationwide Inpatient Sample.19 They discovered that, by the end of their study period, the number of patients who were discharged for UIAs more than doubled. They also discovered that, from 1993 to 2003, the number of patients who underwent placement of surgical clips remained relatively stable (from 12 621 to 12 626), but the number of patients who received endovascular treatment more than doubled in the same time period (from 11 663 to 24 638).
Several recent studies have also directly compared total hospital costs associated with treatment of UIAs. One study by Halkes and colleagues and another study by Hoh and colleagues concluded that endovascular coiling was associated with higher total hospital costs than surgical clipping.3 ,4 A subsequent study by Hoh and colleagues that compared total hospital costs of endovascular coiling and surgical clipping at a national level contradicted their earlier study, concluding that surgical clipping of UIAs was associated with higher total costs.5 Most recently, a study by Lad and colleagues used the MarketScan database to compare costs and complications of patients who underwent surgical clipping or endovascular coiling from 2000 to 2009.7 Their results indicated that surgical clipping was associated with higher initial costs and complications. However, at 2 years and 5 years, overall costs between the two procedures were similar due to the need for follow-up imaging studies and higher outpatient costs for patients who underwent endovascular coiling.
The goal of our study was to provide a clearer picture of the costs associated with the index hospitalization of patients with UIAs who underwent endovascular coiling or microsurgical clipping at our institution. Our hypothesis was that clipping of patients with UIAs at our institution would be associated with longer hospitalization, higher rates of procedure-related morbidity, and therefore higher total hospital costs. Our results indicate that total hospital costs were significantly lower for clipping than for coiling, even though patients treated with surgical clipping experienced longer hospital stays and higher morbidity rates that trended toward significance. Short-term follow-up morbidity rates, however, remained comparable between the two intervention arms. We also hypothesized that the costs of the coils in the form of variable direct costs would overcome any substantial total cost reduction due to shorter length of stay and lower morbidity in patients undergoing coil embolization. Our data support this hypothesis.
We found the following cost relationships to be statistically robust. Patients treated with surgical clipping had higher fixed direct costs, higher fixed indirect costs, and lower variable direct costs. The fact that patients who underwent clipping had higher fixed direct costs and fixed indirect costs is expected as these patients spent longer periods of time in the hospital, during which the hospital accumulates these costs. Variable direct costs, which are largely composed of the material costs associated with either procedure, consistently accounted for the majority of the total hospital costs for patients treated with endovascular coiling but generally only accounted for half of the total hospital costs for patients who underwent surgical clipping. Our regression models showed that length of stay, patient age, and aneurysm size were all significant drivers of hospital costs for patients treated with clipping. Length of stay was a statistically significant driver of hospital costs for patients who underwent coiling, but the explanatory power of the regression model for patients treated with coiling was weak. These results can be attributed to the fact that much of the variation in the total hospital costs for patients treated with coiling is driven by variable direct costs, which we excluded as an independent variable in the regression analyses. We suspect that, in the long-term, if rates of reoperation and follow-up imaging studies were included in the overall cost burden, then coiling would surmount clipping in terms of total hospital costs.
Our cost analysis results disagree with the findings of two recent studies performed using nationwide databases by Hoh and colleagues and Lad and colleagues. One explanation for this discrepancy aside from institutional-level selection bias is that, because both of the recent studies examined cost data during periods (2002–2006 and 2000–2009, respectively) when the volume of endovascular coiling procedures was rapidly rising and the volume of microsurgical clipping procedures was stagnant, these studies may not have fully captured the pricing adjustments made by suppliers of coils in response to new levels of material demands. These pricing adjustments would likely have been fully realized in hospital costs towards the end of these study periods or even afterwards. Because our study analyzes cost data that are relatively up to date, the discrepancy between our cost relationships for aneurysm clipping and coiling and those presented in recent studies may reflect true differences between current cost relationships and cost relationships 5–10 years ago. A recent study by Brinjikji and colleagues showed that, between 2001 and 2008, inflation-adjusted hospital costs associated with surgical clipping of unruptured aneurysms increased by 3.6% annually compared with an annual increase of 4.6% for hospital costs associated with coil embolization. By the end of the study period, the inflation-adjusted costs of coiling had surpassed the inflation-adjusted costs of clipping.20
Despite increased competition among a growing supplier base, coil prices have continued to rise. As suggested by Cloft, continued increases in coil prices can probably be explained by a combination of physicians’ insensitivity to device prices due to lack of relationships between physician salaries and hospital costs, physicians’ willingness to adopt new devices based on marginal theoretical benefits while disregarding costs, and physicians’ fear of being left behind when failing to embrace the latest technologies even when the benefits afforded by the latest technologies are minimal.21 Cloft encourages more skeptical scrutiny among physicians with regard to adopting new products. He also calls for physicians to be more sensitive to the fact that devices in neurointervention often make it to the marketplace with minimal data to support the safety or efficacy of the devices.22
An initiative to increase physician exposure to the costs of the devices they use by linking salaries to device expenses may be a necessary first step towards containing the growing costs associated with endovascular coiling. A recent study by Robinson and Brown23 demonstrated that substantial healthcare pricing efficiencies were realized when the degree of consumer cost sharing increased. More direct exposure to device costs will likely generate incentives for physicians to partner with hospitals in negotiations with vendors to obtain products at competitive prices.
Limitations to this study include its non-randomized retrospective design. However, the demographics of our treatment groups were only significantly different for patient age. Also, our findings only represent cost relationships at a single institution and may not be entirely generalizable at a national level. Future studies would benefit from the use of current cost data, prospective design, and software that can provide investigators with itemized breakdowns of all costs associated with aneurysm clipping or coiling. Future directions would also include comparisons of hospital charges with hospital costs and cost utility analyses that incorporate costs per quality-adjusted life year for patients treated with clipping and coiling.
Conclusion
Although surgical clipping of UIAs is associated with longer hospitalizations and higher rates of morbidity at initial discharge, the total index hospitalization costs associated with clipping are lower than those associated with coiling. Two-month follow-up morbidity rates suggest that short-term morbidity is comparable between the two procedures. Variable direct cost, largely comprised of the cost of the coils and devices, is the main contributor to the total costs of coiling. Strategies that optimize future healthcare utilization should take into account the fact that costs can be stratified and these strata are driven by different variables. Clinical variables are not flexible; device and equipment variables present more opportunity for modification and cost containment.
Acknowledgments
The authors would like to express appreciation and thanks to J T Tan for assistance with cost data acquisition.
References
Footnotes
Contributors YD authored the majority of the manuscript, performed the relevant review of the literature, analyzed the data, and was involved in planning the methods and scope of the project. KB provided editorial assistance, helped with data analysis, and contributed to data collection and interpretation. JN was involved in planning the methods and scope of the project and contributed to initial data collection. WS was involved in planning the methods and scope of the project and assisted with proof-reading the project abstract. NB was involved in planning the methods and scope of the project, contributed to initial data collection, and assisted with the project abstract.
Competing interests None.
Ethics approval The protocol for this study was approved by the University Hospitals Case Medical Center Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.