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Health Policy and Practice |
1 From the Departments of Radiology (J.L.B., J.S.L., P.M.M., M.T.B., E.F.H., J.A.K., G.S.G.) and Vascular Surgery (D.C.B.), Massachusetts General Hospital, Harvard Medical School, Zero Emerson Pl, Suite 2H, Boston, MA 02114; Department of Health Policy and Management, Harvard School of Public Health, Boston, Mass (G.S.G.); and Department of Epidemiology and Biostatistics, Erasmus University Medical Center, Rotterdam, the Netherlands (J.L.B.). Received September 5, 2000; revision requested October 17; final revision received January 30, 2001; accepted February 15. Address correspondence to J.L.B. (e-mail: johanna@the-data-group.org).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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MATERIALS AND METHODS: Total actual cost data for patients undergoing elective endovascular (n = 181) or open surgical (n = 273) repair of abdominal aortic aneurysms between 1997 and 1999 were retrieved. The mean total hospital cost (including stent-graft costs and excluding attending physician fees) and mean postoperative length of stay were calculated for each treatment group. Costs were expressed in 1999 U.S. dollars.
RESULTS: Endovascular repair yielded a shorter postoperative length of stay than did open surgery (mean stay, 3.4 vs 8.0 days; P < .001) and a lower proportion of patients who were admitted to the intensive care unit for 1 full day or longer (2.8% vs 36.3%; P < .001). The mean total hospital cost was significantly higher for endovascular repair than for open surgery ($20,716 vs $18,484; P < .001).
CONCLUSION: Hospital costs were higher for endovascular repair than for open surgical repair. However, endovascular repair was associated with a decreased length of stay and fewer intensive care unit admissions. The increased mean hospital cost for endovascular repair was smaller than one would expect, considering the higher costs of endovascular grafts, as compared with those for surgical grafts (approximately $6,400 according to literature data).
Index terms: Aneurysm, aortic, 981.73 • Aorta, grafts and prostheses, 981.1286 • Aorta, interventional procedures, 981.1286 • Cost-effectiveness • Economics, medical
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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To our knowledge, few studies in which the costs of endovascular and open surgical repairs of AAAs were compared have been published. These studies had differing results (11–15). In some studies, endovascular repair was cheaper, but in others, the opposite was found. Across all of these studies, the ratio of the mean cost of open surgical repair to the mean cost of endovascular repair has ranged from 0.63 to 1.36. The results of most of these studies, however, were based on small patient groups or cost estimates on charges rather than on actual resource utilization.
The primary purpose of this study was to determine and compare the mean in-hospital costs of elective open surgical and endovascular repairs of infrarenal AAAs.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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1.5 cm), absence of major comorbid medical conditions such as metastatic carcinoma, and patient treatment preference (9). In our hospital, the standard imaging examination performed during endovascular procedures was catheter aortography. The typical team (including J.A.K., D.C.B.) that performed the endovascular procedures included one radiology attending physician, one radiology fellow, one surgery attending physician, one surgery fellow, one scrub nurse, one radiologic technologist, one anesthesiologist, and one circulation nurse. A similar team, excluding the radiologists, performed the open surgical procedures. Admission to the intensive care unit (ICU) was not a part of the protocol after an endovascular procedure, whereas patients who underwent open surgery were required to stay in the ICU at least 1 night. Endovascular procedures have been performed in our hospital since 1994. Since then, the senior members of the team (including J.A.K. and D.C.B.), who perform the critical aspects of the procedure, have not changed. The institutional review board of our hospital approved the trial protocols. In addition, informed consent was obtained from all patients included in the trials.
The study patients were retrospectively identified through the hospital accounting system (Transition Systems, subsidiary of Eclypsis, Delray Beach, Fla). This system maintains cost data on all patients and enables the identification of these patients by using ICD-9-CM (International Classification of Diseases, 9th Revision, Clinical Modification) procedure and diagnostic codes (16). In our study, we reviewed the hospital costs related to codes associated with the endovascular and surgical repairs of AAAs. We included patients with the principal diagnosis of AAA without rupture (ICD-9-CM code 441.4) and with the principal procedure codes 38.44 (resection of abdominal aorta with replacement, n = 283), 39.52 (other repair of aneurysm, n = 163), and 39.90 (insertion of noncoronary arterial stents, n = 10). For each patient, we also retrieved information on secondary diagnoses, all procedures performed during the hospital stay, patient demographics (age and sex), deaths during the hospital stay, total number of days in the hospital, and number of days spent in the ICU. It should be noted that our system is limited to the inclusion of no more than 10 secondary diagnoses or procedures; in our study group, however, no more than seven per patient were reported.
On the basis of administrative data, coexistent morbidities and complications were defined by using published coexistent disease and complication measures (17). These measures enable one to identify coexistent diseases and complications on the basis of secondary-diagnosis ICD-9-CM codes (16). Coexistent morbidity was defined as a clinical condition that existed before a patient’s admission to the hospital, was not related to the principal reason for the hospitalization, and was likely to be an important factor that influenced mortality and resource use in the hospital (17). Complications were defined as acute conditions that could result from the performance of medical procedures (17). This classification has been described in detail previously (17). Furthermore, we identified the secondary (noncardiac) vascular procedures, such as balloon angioplasty or bypass, performed in each patient on the basis of the secondary-procedure codes (ICD-9-CM 38 and 39).
To validate the accuracy of the coding and the classifications of coexistent morbidities and complications, two authors (J.L.B., M.T.B.) reviewed 50 patients’ charts that were randomly selected from the study group. In this review, we found that the complications, coexistent morbidities, and mortality were correctly coded for 47 patients (94%). In two patients, no complications were indicated; however, in their charts, we found that one patient was treated for a hematoma and the other was treated for an unrelated complication (ie, acidosis). The third patient was coded with a complication; however, no complication was recorded in this patient’s chart.
Two hundred seventy-four patients underwent open surgical repair, whereas 182 underwent endovascular repair. One hundred three (57%) of the 182 endovascular procedures were performed by using commercially available stents, and the remaining 79 (43%) procedures were performed by using custom-made stents. Tube stents were used in 15 (8%) of the 182 procedures; bifurcated stents, in 117 (64%) procedures; and aortounilateral iliac arterial stents with concomitant femoral-to-femoral bypass, in 50 (27%) procedures.
Hospital Costs
Financial data were retrieved from the hospital cost accounting system (Transition Systems), a database into which all hospital financial data are entered. In the absence of microcost analysis, the costs derived from this system are often considered the reference standards (18). Details on this cost-accounting system have been described elsewhere (18). We retrieved the total hospital actual costs per patient, which include direct (both fixed and variable) and indirect (eg, building depreciation and information systems) expenses. The expenses incurred by a particular patient are identified through the billing system and then converted to intermediate products. Actual costs are assigned to these intermediate products, which are based on volume and relative value units. Hospital costs include those for disposable supplies, labor, and major capital depreciation and overhead. Disposable supply costs are based on actual acquisition costs. The labor costs for nurses, technicians, fellows, residents, secretaries, orderlies, and other personnel are derived directly from actual salaries and include benefits. It should be noted that attending physician fees are not included in the cost accounting system database and were not included in this analysis, which, in essence, focused on the hospital component of costs.
Major depreciation and overhead costs are measured on the basis of factors such as patient volume and square footage. Furthermore, the costs of the endovascular stent devices used in clinical trials are not included in the hospital accounting database. Because of its artificiality in clinical trials and because market prices were not established, we added a stent cost of $7,000—which is within the range of stent costs reported in the literature (11,13,14)—to the total actual costs of all patients enrolled in clinical trials—that is, those patients in whom commercially available stents were placed. The costs of the supplies for the custom-made stents were included in the total actual costs.
All costs were calculated per patient and expressed in U.S. dollars. Costs from prior years were converted to 1999 dollars by using the Medical Component of the Consumer Price Index (19).
Data Analysis
Patient characteristics, complications, mortality rates, secondary vascular procedures, ICU admissions, and ICU lengths of stay of patients undergoing endovascular repair and open surgical repair were compared by using the Student t test and the 
2 test (
= .05). Mean hospital costs and postoperative lengths of stay for endovascular repair and open surgical repair were analyzed per treatment group, including all patients, and per treatment group, excluding patients with complications and patients who died during the hospital stay.
To determine the effect of covariates on the total actual costs and postoperative lengths of stay, stepwise multiple linear regression analysis (entry criterion, P = .05; removal criterion, P = .10) was performed with a statistical software package (SPSS for Windows, version 9.0.0; SPSS, Chicago, Ill). Four models were fitted to evaluate variations in total actual costs and postoperative lengths of stay.
In the first model, we used total actual hospital costs as the dependent variable. The principal procedure (ie, open surgical repair vs endovascular repair) was included as an independent variable in the model, as were patient characteristics (ie, age and sex), postoperative length of stay (in rounded days), and length of stay in the ICU (in rounded days if 1 full day). Additional independent covariates indicating the presence of any coexistent morbidity, complications, in-hospital mortality, and/ or secondary vascular procedures were included. To investigate whether the costs of the principal procedure depended on the presence of complications or mortality, we included interaction terms (ie, the interaction of principal procedure and complication and the interaction of principal procedure and mortality) in the model. To analyze whether the costs changed over time, we included the year in which the procedure was performed (1997–1999) as a covariate in the model. In the second model, we investigated the influence of these covariates on postoperative length of stay. In this model, we excluded postoperative length of stay and stay in the ICU as possible covariates.
The third and fourth multiple linear regression analysis models were limited to patients undergoing endovascular repair (n = 181). For these models, we added indicators for the type of stent (ie, tube or bifurcated vs aortounilateral, and commercial vs custom made) to the list of independent variables to investigate their influence on total actual costs and postoperative length of stay. All analyses were performed with a computer software program (SPSS for Windows, version 9.0.0).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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The mean age of the 181 patients who underwent endovascular repair was significantly higher than that of the 273 patients who underwent open surgical repair (75.0 years ± 7.8 [SD] vs 73.0 years ± 7.9; P = .007). Otherwise, there were no significant differences in the patients’ characteristics. Three hundred sixty four (80%) of the 454 patients were men, and 276 (61%) had hypertension; 49 (11%), diabetes; 37 (8%), congestive heart failure; 71 (16%), cardiac arrhythmia; 99 (22%), chronic pulmonary disease; 17 (4%), renal failure; and 88 (19%), peripheral vascular disorders.
Complications occurred in 25 (9.2%) of 273 patients in the open surgery group and in 11 (6.1%) of 181 patients in the endovascular repair group (P = .23). Eight (2.9%) of 273 patients in the open surgery group died before hospital discharge, as compared with two (1.1%) of 181 patients in the endovascular group (P = .33). Secondary vascular procedures were more frequently reported in the endovascular group than in the open surgery group (132 [72.9%] of 181 patients vs 89 [32.6%] of 273 patients, P < .001). In the open surgery group, 99 (36.3%) of 273 patients stayed 1 day or longer in the ICU; in the endovascular repair group, five (2.8%) of 181 patients stayed 1 day or longer in the ICU (P < .001). For the patients who underwent open surgical repair and stayed 1 day or longer in the ICU, the mean ICU stay was 2.3 days ± 2.1 (median, 1.0 day; range, 1.0–12.0 days); for those who underwent endovascular repair, the mean ICU stay was 1.2 days ± 0.4 (median, 1.0 day; range, 1.0–2.0 days).
The mean hospital cost, including costs for all admissions for AAA repair, was significantly lower for open surgical repair than for endovascular repair ($18,484 ± 8,885 vs $20,716 ± 6,070; P = .003) (Table 1). When the patients who died during the hospital stay and the patients with complications were excluded, the hospital costs were similar: The mean hospital cost was lower for open surgical repair than for endovascular repair ($18,208 ± 8,375 and $20,348 ± 5,462, respectively; P = .002).
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According to multiple linear regression analysis data, it was estimated that after adjustment for covariates, endovascular repair caused an increase in hospital costs but a reduction in postoperative lengths of stay, as compared with open surgical repair. The model shows that if all other variables were assumed to be equal, hospital costs would increase by $7,489 and postoperative lengths of stay would decrease by 5.2 days (Table 2). Other variables that increased hospital costs were secondary vascular procedures (by $3,570, if performed), postoperative length of stay (by $1,191 per day), ICU stay 1 full day or longer (by $1,483 per day), and mortality (by $8,693). Furthermore, costs increased over time ($810 per year). Other variables that increased the postoperative length of stay were secondary vascular procedures (by 1.5 days), complications (by 1.3 days), and age (0.7 day per decade). Finally, the postoperative length of stay changed significantly over time (reduced by 0.5 day per year). The inclusion of interaction terms, which indicated additional differences between the treatment groups, did not improve the goodness of fit of these models.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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The multiple regression analysis estimate of the additional mean cost of AAA repair when an endovascular procedure rather than open surgery was performed was $7,489 after adjustment for covariates. This means that if the two procedures resulted in the same length of hospital stay and same ICU stay, then the costs for endovascular repair would be $7,489 higher than those for open surgical repair. However, although endovascular procedures resulted in less time in the ICU and shorter postoperative hospital stays, the actual difference in mean hospital cost was considerably smaller although significant. It is likely that the higher endovascular repair costs were related to the procedure itself. More specifically, the higher costs for endovascular repair might be attributed largely to differences in the costs of the grafts. According to literature data, the cost of the graft is approximately $600 with open surgery and $7,000 with endovascular repair (11,13–15). In addition, on the basis of these estimates from the literature, graft costs represent approximately 34% ($7,000/$20,716) and 3% ($600/$18,484) of the total procedural costs for endovascular and open surgical repairs, respectively.
Another finding of our study was that an endovascular procedure that included aortounilateral iliac artery stent placement increased hospital costs relative to one that included tube or bifurcated stent placement. This procedure may be more expensive because it is more complex and possibly requires more procedural time. Furthermore, we found that commercially available stents were more expensive than custom-made stents. These results, however, should be interpreted with caution, because we included a fixed cost estimate for the commercially available stents.
Furthermore, the costs and postoperative lengths of stay changed over time. As new techniques are developed and practice patterns evolve, one can expect costs and lengths of stay to change correspondingly. Therefore, an unexpected finding was that although postoperative lengths of stay decreased over time, hospital costs increased over time. However, in the analysis limited to the patients treated with only endovascular stents, the hospital costs did not change over time. Thus, the change in costs over time occurred in the open surgical repair group. It should be noted that all costs were converted to 1999 U.S. dollars by using the Medical Component of the Consumer Price Index (19), and, thus, the increase in costs cannot be explained by inflation (assuming that the consumer price index adequately adjusts for inflation).
In other studies in which the costs and lengths of stay were compared between elective endovascular repair and open surgical repair for AAAs, the results were similar to ours with respect to length of stay (11–14). The hospital costs for the treatment groups, however, varied among these studies. Some investigators reported that costs were lower for endovascular repair than for open surgical repair, while others concluded that it was unlikely that endovascular repair would lead to cost savings. Unlike estimates in previously reported studies, however, our cost estimates were based on actual costs rather than on charges. In addition, our study included a larger patient group than those in previously reported studies.
Our study had several potential limitations. First, we identified patients and derived coexistent morbidity and complication data from the hospital administrative database by using ICD-9-CM codes, and we applied published measures of ICD-9-CM secondary diagnosis codes to define these variables (17). All the patients in our study had a diagnosis of AAA without rupture and therefore were assumed to have undergone elective treatment. However, we were unable to identify those patients who may have had acute abdominal pain or received urgent treatment. Furthermore, the complication and mortality rates in our study were not significantly different between the endovascular repair and open surgical repair groups, and both rates were low compared with those in other studies (1,20).
We performed a review study of the patients’ charts to check the validity and accuracy of the coding and found that in 47 (94%) of 50 patients, the coding was correct. In the three remaining patients, errors in the coding of complications were found: both false-positive and false-negative cases. Green and Wintfeld (21) found a decrease in coding error rates during the 1970s and 1980s and reported that the principal diagnosis was inaccurately coded in 9% of records. However, higher rates of inaccurate coding and concerns about the accuracy of ICD-9 coding have been reported in other studies (22,23). Because our review study was limited to 50 patients, the exact rate of accuracy of the data used in our study is unknown.
Another limitation of our study was that open surgery for abdominal aneurysm repair has been performed for decades, whereas endovascular repair is a recently introduced technique. Because the endovascular procedure is newer and more rapidly evolving, the eventual costs of endovascular repair may have been overestimated owing to, for example, longer-than-necessary procedural times or more personnel being present during the procedure. As endovascular procedures develop over time, it is likely that they will be performed more efficiently and thus yield decreased hospital costs. In addition, our selection criteria may have biased the results. Although the proportions of coexistent morbidities between the patients treated with open surgical repair and those treated with endovascular repair were not significantly different, a randomized clinical trial should be performed to investigate the differences between these treatments more accurately.
Other limitations of our study included the use of a fixed estimate of the cost of the commercially available endovascular stent-grafts. It is likely that the cost of these stents will vary according to type and configuration. In addition, we included only the supply costs of the custom-made stents. The physician time required to make the graft was not determinable, and, therefore, we may have underestimated the costs of procedures with custom-made stents. Also, we excluded two patients with costs and lengths of stay that were significantly greater than those of the other 454 patients. Because these two patients were from one of each treatment group, it is unlikely that the exclusions altered the estimated incremental effect to a large extent. However, their exclusion may have resulted in a slight underestimation of the mean total cost and mean postoperative length of stay in our study.
Finally, in this study we performed a cost analysis that excluded attending physicians’ fees, future medical care costs, production losses, and costs borne by patients or family members. Including these variables, for example, in an analysis performed from a societal perspective may enable the identification of additional differences between endovascular and surgical repair.
In conclusion, elective endovascular repair of AAAs, as compared with open surgical repair, was associated with a decreased length of hospital stay and fewer ICU admissions. Total procedural costs were higher for endovascular repair than for open surgical repair. However, the increase in the mean hospital cost for endovascular repair was smaller than expected owing to the higher costs of endovascular grafts, as compared with those for surgical grafts (approximately $6,400 according to data in the literature).
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FOOTNOTES |
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Author contributions: Guarantors of integrity of entire study, J.L.B., G.S.G.; study concepts, all authors; study design, J.L.B.; literature research, J.L.B., J.S.L.; clinical studies, J.L.B., M.T.B., J.A.K., D.C.B.; data acquisition, J.S.L., J.A.K., D.C.B.; data analysis/interpretation, J.L.B., E.F.H., G.S.G.; statistical analysis, J.L.B., E.F.H.; manuscript preparation, J.L.B.; manuscript definition of intellectual content and editing, J.L.B., E.F.H., G.S.G.; manuscript revision/review and final version approval, all authors.
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REFERENCES |
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