Independent Determinants for Increased Hospital Costs and Length of Stay in Open Appendectomy in Comparison with Laparoscopic Appendectomy:
A Nationwide Cohort Study
CHUN-CHIEH YEH, M.D.,*†‡ CHI-HSUN HSIEH, M.D.,† CHIEN-CHANG LIAO, PH.D.,§k LI-TING SU, M.S.,†§
YU-CHUN WANG, M.D.,† TSAI-CHUNG LI, PH.D.{**††‡‡§§
From the *Graduate Institute of Clinical Medical Science, China Medical University, Taichung, Taiwan;
†Trauma and Emergency Center, China Medical University Hospital, China Medical University, Taichung, Taiwan; the ‡Department of Surgery, China Medical University Hospital, Taichung, Taiwan; the §Management Office for Health Data, China Medical University Hospital, Taichung, Taiwan; the kDepartment of Anesthesiology, Taipei Medical University Hospital, Taipei, Taiwan; the {Graduate Institute of Biostatistics, College of Public Health, China Medical University, Taichung, Taiwan; the **Graduate Institute of Chinese Medicine Science, College of Chinese Medicine, China Medical University, Taichung, Taiwan; the
††Biostatistics Center, China Medical University, Taichung, Taiwan; the ‡‡Department of Medical Research, China Medical University Hospital, Taichung, Taiwan; and the §§Institute of Health Care Administration, College of Health Science, Asia University, Taichung, Taiwan
Comorbidity has been proven to increase hospital costs and length of hospital stays in patients receiving appendectomy for the treatment of acute appendicitis. However, the specific comor- bidities that independently influence discrepancy of hospital costs and length of stay between open appendectomy and laparoscopic appendectomy still need to be elucidated. Using multi- variate linear analysis, administrative claims data were obtained from Taiwan’s National Health Institute Research Database to compare differences of hospitalization costs and length of stay between open appendectomy and laparoscopic appendectomy categorized by various comorbid- ities defined in Charlson comorbidity score. Of 103,653 patients, 81,479 open appendectomies and 22,174 laparoscopic appendectomies were performed for the treatment of acute appendicitis in Taiwan between 2004 and 2008. In multilinear regression models, the adjusted costs and length of stay for open appendectomy in patients with cerebrovascular diseases or diabetes mellitus were significantly higher than that for laparoscopic appendectomy. To reduce costs and length of stay, patients with cerebrovascular diseases or diabetes mellitus should be particularly recom- mended to receive laparoscopic approach rather than an open approach for the treatment of acute appendicitis.
A
CUTE APPENDICITIS IS a common surgical disease with an incidence of 10 per 10,000 persons per year.1 Open appendectomy had been a standard treat- ment for acute appendicitis for more than a century. In the early 1980s, laparoscopic appendectomy was in- troduced as an alternative procedure for the treatment of appendicitis.2The safety of laparoscopic appendectomyin patients with acute appendicitis has been proven already.3, 4However, the benefits of laparoscopic ap- pendectomy in cost-savings in comparison to open appendectomy are still inconclusive, particularly in patients with comorbidities.3, 5, 6
Improvement in health care brings longer life ex- pectancy, which subsequently leads to an increased number of elderly patients with acute appendicitis.7 The elderly patients not only have less physiological reserve, but also more comorbidities, which could cause higher morbidity and mortality rates while treating their acute appendicitis.8, 9 Comorbidity has
Address correspondence and reprint requests to Tsai-Chung Li, Ph.D., Professor, China Medical University Graduate Institute of Biostatistics, 91 Hsueh-Shih Road 15F, Taichung 404, Taiwan. E- mail: tcli@mail.cmu.edu.tw.
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been proven as an independent determinant of costs and length of stay in surgical patients.10 However, limited studies investigated which comorbidities are independent determinants to influence costs and length of stay in patients undergoing open appendectomy and laparoscopic appendectomy.
The Charlson comorbidity score, adapted by Deyo, is a well-accepted age–comorbidity combined risk score and is a useful index to predict postoperative compli- cation rates, mortality, length of stay, and hospital charges in elective surgery.11, 12 To determine which comorbidities are independent determinants on costs and length of stay of laparoscopic appendectomy and open appendectomy, we conducted a nationwide cohort study to compare differences of costs and length of stay between laparoscopic appendectomy and open appen- dectomy stratified according to the comorbidities de- fined by Charlson scores.
Patients and Methods Data Source
This study was a nationwide, population-based anal- ysis of insurance claims data from the 23 million insured people of Taiwan’s National Health Insurance program, which is almost the entire Taiwanese population. We acquired all claims data obtained from the National Health Institute Research Database (NHIRD). The Na- tional Health Insurance program in Taiwan is a universal insurance system organized by the Bureau of National Health Insurance in the Department of Health. The in- surance program was carried out in March 1995, and by 1996, it included more than 96 per cent of the pop- ulation.13 The patient information that was recorded included all medical services received in 1996 to 2008, personal characteristics of patients, and characteristics of hospitals. The patient identification numbers linked to their identities were scrambled to ensure patient confi- dentiality. For this study, we used information including date of birth, sex, main diagnosis and procedure at ad- missions, hospital charges, length of stay, coexisting illness, urbanization of admitting hospitals, admission hospital level, and patients’ discharge status.
Participants
Since laparoscopic appendectomy became popular in Taiwan after 2004, the database between 2004 and 2008 were used in this study. All diagnosis and pro- cedural codes were made according to the International Classification of Diseases, Ninth Edition, Clinical Modification (ICD-9-CM). Patients who were diagnosed with acute appendicitis and received appendectomies were identified through patient claims data of NHIRD
using ICD-9-CM codes. Inclusion criteria included ICD-9-CM diagnosis codes 540.0, 540.1, 540.9, 541, and 542 combined with ICD-9-CM procedure codes 47.01 and 47.09. Exclusion criteria were those appendiceal diseases other than appendicitis (ICD- 9-CM 543.9 and 127.4) and those patients who re- ceived incidental appendectomy (ICD-9-CM 47.1, 47.11, and 47.19). In addition, we also excluded outlier patients with extremely high hospital costs (the top 1%
of patients with the highest hospital costs).
Outcome of Measurement Length of Stay
The duration between admission and discharge dates was calculated as the length of stay (measured in days).
Length of stay was recorded as ‘‘1’’ if patients were discharged on the same day of admission.
Hospital Costs
The hospital costs were calculated by summing fees for all medical supplies and expanses in the hospital.
Costs expressed in this study were in U.S. dollars ($1 U.S. was approximately $31.52 in Taiwanese currency in 2008).
Covariates
The covariates included age, gender, severity of appendicitis (complicated vs uncomplicated appendi- citis), and comorbidities as well as hospital level (medical center vs regional hospital vs district hospital) and urbanization of hospital (low vs moderate vs high).
Complicated appendicitis was defined as appendicitis with perforation, abscess formation, or peritonitis (ICD-9-CM 540.0 and 540.1). On the other hand, pa- tients ICD-9-CM codes of 540.9, 541, and 542 were defined as uncomplicated appendicitis. To evaluate the concerted influence of age and comorbidities, we used the Charlson comorbidity score as a substitute for age and comorbidities. The comorbidities we considered were total coexisting illnesses defined by Charlson comorbidity scores and ICD-9-CM codes were used to identify those comorbidities defined in Charlson scoring system.11, 12There were 319 city districts and townships in Taiwan and the population density were defined by dividing population with residence area (person/km2). The first quartile and the fourth quartile of population density were categorized as areas of low and high urbanization, respectively, whereas the sec- ond and the third quartiles of population density were considered as moderate urbanization. The urbanization of hospitals was defined corresponding to the urbani- zation level of their locations.
Data Analysis
First, to compare characteristics of patients receiv- ing either open appendectomy or laparoscopic appen- dectomy, the distributions of the sociodemographic status, severity of appendicitis, Charlson comorbidity score, and comorbidities defined in the Charlson scoring system were demonstrated. Second, after adjusting for gender, hospital level, urbanization of the hospital, and severity of appendicitis, we compared the adjusted hospital costs and length of stay between open appendectomy and laparoscopic appendectomy and tested the linear trends of the discrepancy among subpopulations of patients with different Charlson comorbidity scores. Subsequently, we used univariate analysis to verify specific comorbidities defined in the Charlson score that had a significant impact on costs and length of stay for laparoscopic appendectomy and open appendectomy. We also compared the difference of adjusted costs and length of stay between laparo- scopic appendectomy and open appendectomy by each comorbidity. Multiple linear regression models were used to evaluate the difference of adjusted costs and length of stay between open appendectomy and laparo- scopic appendectomy in patients with various comor- bidities. Because comorbidity defined in the Charlson comorbidity score often coexists in the same patient, after adjusting for gender, severity of appendicitis, hospital level, and urbanization of hospital, Charlson comorbidity scores were also used as a covariate for adjustment in each regression model. All analyses used SAS software Version 9.1 (SAS Institute Inc., Cary, NC). The statistically significant level was set at 0.05 by a two-tailed test.
Results
Between 2004 and 2008, 103,653 patients under- went appendectomies and 45 per cent of them were women. Among these patients, 81,479 of them received open appendectomy and 22,174 by laparoscopic ap- pendectomy (Table 1). In comparison with patients undergoing open appendectomy, more patients under- going laparoscopic appendectomy lived in highly ur- banized areas (83.9 vs 74.8%, P < 0.001) and were treated in medical centers (49.1 vs 29.4%, P < 0.001).
The mean length of stay was higher in patients un- dergoing open appendectomy than patients undergoing laparoscopic appendectomy (5.9 ± 0.1 vs 4.2 ± 0.1 days, P < 0.001). However, average hospital costs were slightly higher in patients undergoing laparoscopic appendec- tomy than in patients undergoing open appendectomy (1221 ± 6 vs 1215 ± 5 U.S. dollars, P < 0.001).
The differences of adjusted hospital costs between open appendectomy and laparoscopic appendectomy also increased in patients with higher Charlson comorbidity
scores (P for linear trend 4 0.003) (Fig. 1A). In ad- dition, there was a significant interaction between types of operation and Charlson comorbidity score (P for interaction < 0.001). Adjusted costs of open ap- pendectomy were significantly less than laparoscopic appendectomy in populations with Charlson comor- bidity scores of 1. In patients with Charlson comor- bidity scores of 2 to 4, the adjusted costs for open appendectomy and laparoscopic appendectomy were similar. Furthermore, in patients with Charlson comorbidity scores of 5 and beyond, adjusted costs of open appendectomy became significantly higher than laparoscopic appendectomy. Nonetheless, adjusted length of stay of open appendectomy was universally longer than laparoscopic appendectomy in each group of pa- tients with different Charlson comorbidity scores. The discrepancy of adjusted length of stay between open appendectomy and laparoscopic appendectomy became larger as Charlson comorbidity scores increased (P for linear trend < 0.05), whereas there is also an interaction between operative types and Charlson comorbidity scores on adjusted length of stay (P for interaction <
0.05) (Fig. 1B).
An univariate analysis (Table 2) revealed that myo- cardial infarction, congestive heart failure, cerebro- vascular disease, chronic pulmonary disease, mild liver disease, diabetes mellitus, moderate or severe renal disease, and AIDS were determinants for differences in unadjusted costs between open appendectomy and lap- aroscopic appendectomy. In patients who had any one of these comorbidities, unadjusted costs for open appen- dectomy were significantly higher than laparoscopic appendectomy. Similarly, these comorbidities, except mild liver disease, were also determinants of differences in unadjusted length of stay between open appendec- tomy and laparoscopic appendectomy. The unadjusted length of stay of open appendectomy was significantly longer than that of laparoscopic appendectomy if pa- tients had certain comorbidities.
After adjusting for gender, severity of appendicitis, Charlson comorbidity score, hospital level, and ur- banization of hospital, the results of multiple linear regression models (Table 3) demonstrated that cerebro- vascular disease, chronic pulmonary disease, and diabetes mellitus were independent determinants for differences in adjusted costs between open appendectomy and laparo- scopic appendectomy. Likewise, cerebrovascular disease and diabetes mellitus were independent determinants for differences of adjusted length of stay between open ap- pendectomy and laparoscopic appendectomy.
Discussion
With a longer life expectancy in modern times, comorbid conditions become important determinants
of clinical and economic outcomes in healthcare sys- tems.10 By using a nationwide data set, our results indicated that patients with diabetes mellitus and ce- rebrovascular disease benefited from laparoscopic appendectomy rather than open appendectomy in the treatment of acute appendicitis in terms of reduced hospital costs and length of stay.
Comorbidities such as cerebrovascular disease, chronic pulmonary disease, and diabetes mellitus have been reported as determinants of increased postoperative complications and length of stay in laparoscopic
surgeries.10, 14–16 After statistical adjustment for the severity of appendicitis and Charlson comorbidity scores between groups, we found that cerebrovascular disease and diabetes mellitus were independent de- terminants for the increased costs and length of stay after open appendectomy than that of laparoscopic appendectomy. These results were consistent with pre- vious studies reported by Cho,10 Cheng,14 Kim,15and Ming et al.16In addition, the reason to use the Charlson comorbidity score instead of specifying comorbidi- ties for regression analysis was to avoid too many TABLE1. Sociodemographic Characteristics of Patients with Appendicitis and Receiving Appendectomy Between 2004 and 2008
Variable
Appendicitis
OA (n 4 81,479) LA (n 4 22,174)
No. (%) No.(%)
Age, years (mean ± SE) 35.6 ± 0.1 34.0 ± 0.1
Gender, no. (%)
Women 35,956 (44.1) 10,775 (48.6)
Men 45,523 (55.9) 11,399 (51.4)
Hospital level, no. (%)
Medical center 23,980 (29.4) 10,883 (49.1)
Regional hospital 40,550 (49.8) 9,414 (42.4)
District hospital 16,949 (20.8) 1,877 (8.5)
Urbanization, no. (%)
Low 4,609 (5.7) 1,259 (5.7)
Moderate 15,901 (19.5) 2,299 (10.4)
High 60,969 (74.8) 18,616 (83.9)
Mean length of stay, days (mean ± SE) 5.9 ± 0.1 4.2 ± 0.1
Mean hospital cost, U.S. $ (mean ± SE) 1,215 ± 5 1,221 ± 6
Complicated appendicitis rate, no. (%) 20,668 (25.4) 4,022 (18.1)
Average mortality, no. (%) 107 (0.13) 8 (0.04)
Routine discharge rate, no. (%) 80,837 (99.2) 22,070 (99.5)
Charlson comorbidity score
1 62,558 (76.8) 17,817 (80.3)
2 7,382 (9.1) 2,023 (9.1)
3 4,331 (5.3) 1,033 (4.7)
4 3,127 (3.8) 656 (3.0)
5 1,947 (2.4) 344 (1.5)
6 1,030 (1.3) 170 (0.8)
7 or greater 1,104 (1.4) 131 (0.6)
Comorbidity defined in Charlson scoring system
Myocardial infarctiony 191 (0.2) 29 (0.1)
Congestive heart failure 219 (0.3) 29 (0.1)
Peripheral vascular disease* 284 (0.4) 48 (0.2)
Cerebrovascular disease 1,794 (2.2) 307 (1.4)
Dementia* 105 (0.13) 14 (0.06)
Chronic pulmonary disease* 2,612 (3.2) 494 (2.2)
Rheumatologic disease* 200 (0.2) 52 (0.2)
Peptic ulcer disease 1,046 (1.3) 184 (0.8)
Mild liver disease 898 (1.1) 176 (0.8)
Diabetes mellitus 3,456 (4.2) 692 (3.1)
Hemiplegia or paraplegia* 329 (0.4) 59 (0.3)
Renal disease* 492 (0.6) 72 (0.3)
Any malignancy 502 (0.6) 82 (0.4)
Moderate or severe liver disease 131 (0.2) 24 (0.1)
Metastatic solid tumor 128 (0.2) 18 (0.1)
AIDS 19 (0.02) 3 (0.01)
OA, open appendectomy; LA, laparoscopic appendectomy; SE, standard error.
* Asterisked diseases were included if listed during index or prior admissions.
y Myocardial infarction included both acute and old myocardial infarction. Acute myocardial infarction (International Clas- sification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] 410 to 410.9) was only included if recorded before the index admission. In contrast, old myocardial infarction (ICD-9-CM 412) was included if listed during the index or prior admission.
parameters in regression models that may lead to in- correct statistic calculation. Furthermore, we found that some comorbidities such as myocardial infarction, congestive heart failure, moderate to severe renal
disease, and AIDS were modifiers in univariate anal- ysis but not in multivariate analysis. A possible explanation was that the prevalence of these comor- bidities was too low to achieve adequate statistic power. Thus, if we could collect more cases with these specific comorbidities, we may be able to draw more positive conclusions regarding these comorbidities as significant modifiers for discrepancy of costs and length of stay between open appendectomy and laparoscopic appendectomy.
There were limitations in our study. First, inaccurate coding is possible in such a large, population-based database. However, inaccurate coding theoretically appeared with similar frequency in both open appen- dectomy and laparoscopic appendectomy groups;
therefore, the discrepancy of costs and length of stay between laparoscopic appendectomy and open ap- pendectomy can be minimized but cannot be biased. In addition, data on postoperative complications and re- covery time were not collected in this database and could not be analyzed. With the limitations of this database, we focused our study on the analysis of costs and length of stay after open appendectomy or lapa- roscopic appendectomy without answering other clin- ically relevant questions such as whether laparoscopic appendectomy rather than open appendectomy was associated with a lower incidence of postoperative complications and reduced postoperative recovery time as well as time of returning to work.
In conclusion, this is a nationwide cohort study to evaluate which comorbidities could influence eco- nomic outcomes between open appendectomy and laparoscopic appendectomy for acute appendicitis. In
FIG. 1. (A) Comparison of costs between OA and LA for acute appendicitis. Adjusting for gender, hospital level, urbanization of hospital, and severity of acute appendicitis. P for linear trend < 0.01.
P for interaction < 0.001; *OA vs LA, P < 0.05. Significance established at multiple linear regression models. (B) Comparison of LOS between OA and LA for acute appendicitis. Adjusting for gender, hospital level, urbanization of hospital, and severity of acute appendicitis. P for linear trend < 0.05; P for interaction < 0.05; *OA vs LA, P < 0.05. Significance established at multiple linear regression models. OA, open appendectomy; LA, laparoscopic appendectomy.
TABLE2. Unadjusted Costs and Length of Stay for Either OA or LA Stratified by Specific Comorbidity Defined by Charlson Scores
Stratified comorbidity
Unadjusted Costs (U.S. dollars) Unadjusted Length of Stay (days)
OA LA OA LA
Mean ± SE Mean ± SE P Mean ± SE Mean ± SE P
Myocardial infarction 2,933 ± 331 1,878 ± 295 0.019 10.8 ± 0.9 5.7 ± 0.6 <0.001 Congestive heart failure 4,901 ± 430 2,875 ± 574 0.006 18.2 ± 1.6 7.8 ± 1.0 <0.001 Peripheral vascular disease 2,414 ± 202 2,164 ± 571 0.647 10.5 ± 1.2 17.4 ± 11.3 0.549 Cerebrovascular disease 2,501 ± 84 1,861 ± 113 <0.001 11.2 ± 0.4 7.5 ± 0.7 <0.001
Dementia 4,063 ± 546 3,101 ± 1,121 0.537 22.3 ± 7.7 11.2 ± 3.6 0.194
Chronic pulmonary disease 1,999 ± 61 1,482 ± 74 <0.001 10.0 ± 0.7 6.2 ± 0.9 <0.001 Rheumatologic disease 1,818 ± 251 1,364 ± 81 0.086 12.9 ± 6.0 4.7 ± 0.5 0.178 Peptic ulcer disease 2,480 ± 110 2,094 ± 246 0.170 11.9 ± 0.6 10.5 ± 2.5 0.585 Mild liver disease 2,193 ± 114 1,746 ± 185 0.040 11.9 ± 1.6 9.1 ± 3.1 0.433 Diabetes mellitus 2,087 ± 49 1,718 ± 81 <0.001 9.6 ± 0.3 7.0 ± 0.8 0.003 Hemiplegia or paraplegia 3,470 ± 282 2,965 ± 725 0.491 15.1 ± 1.2 14.9 ± 4.8 0.968 Moderate or severe renal disease 2,828 ± 175 2,239 ± 222 0.038 11.1 ± 0.6 7.9 ± 1.2 0.043 Any malignancy 4,145 ± 227 3,873 ± 657 0.662 15.8 ± 0.8 14.6 ± 2.8 0.683 Moderate or severe liver disease 3,333 ± 417 2,478 ± 1,116 0.431 12.0 ± 1.1 27.2 ± 22.7 0.509 Metastatic solid malignancy 4,518 ± 401 3,150 ± 676 0.092 41.2 ± 16.9 13.8 ± 3.6 0.115
AIDS 3,596 ± 890 1,661 ± 238 0.049 13.4 ± 3.2 4.3 ± 0.7 0.013
OA, open appendectomy; LA, laparoscopic appendectomy; SE, standard error; two-sample Student t test was used to compare costs and length of stay between OA and LA in patients with specific comorbidity.
terms of reducing hospital costs and length of stay, patients with diabetes mellitus and cerebrovascular disease should be recommended to receive laparo- scopic appendectomy as the treatment of choice for acute appendicitis.
Acknowledgments
This study was supported partly by the Executive Yuan National Science Council in Taiwan, Republic of China (grant number NSC 97-2625-M-039-003), the China Med- ical University Hospital (grant number 1MS1), and the Taiwan Department of Health Clinical Trials and Research Centre for Excellence (grant number OH100-TD-B-111- 004) and Cancer Research Centre of Excellence (grant number DOH100-TD-C-111-005).
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TABLE3. Discrepancy of Adjusted Costs and Length of Stay Between OA and LA Stratified by Specific Comorbidity Defined by Charlson Scores
Costs (U.S. dollars) Length of Stay (days)
OA vs LA OA vs LA
Stratified Comorbidity Coefficient (SE) P Coefficient (SE) P
Myocardial infarction 752 (879) 0.394 3.7 (2.4) 0.126
Congestive heart failure 1,710 (1,208) 0.158 8.7 (4.6) 0.060
Peripheral vascular disease –148 (536) 0.782 –9.0 (5.5) 0.106
Cerebrovascular disease 468 (207) 0.023* 3.0 (0.9) 0.001*
Dementia 786 (1,583) 0.621 8.6 (22.1) 0.698
Chronic pulmonary disease 282 (141) 0.045 2.7 (1.6) 0.091
Rheumatologic disease 213 (496) 0.668 0.9 (11.9) 0.939
Peptic ulcer disease 119 (273) 0.662 0.04 (1.7) 0.980
Mild liver disease 371 (262) 0.158 2.4 (3.9) 0.536
Diabetes mellitus 225 (114) 0.049* 1.9 (0.8) 0.014*
Hemiplegia or paraplegia –172 (740) 0.816 –1.0 (3.5) 0.778
Moderate or severe renal disease 440 (458) 0.338 2.6 (1.5) 0.088
Any malignancy including leukemia and lymphoma 183 (620) 0.767 0.53 (2.4) 0.823
Moderate or severe liver disease 837 (1,037) 0.421 –16.1 (9.9) 0.104
Metastatic solid malignancy 1,566 (1,129) 0.168 34.9 (46.1) 0.450
AIDS 744 (2,281) 0.749 5.1 (8.3) 0.546
* P < 0.05.
OA, open appendectomy; LA, laparoscopic appendectomy; SE, standard error; adjusting for gender, hospital level, urbanization of hospital, severity of acute appendicitis, and Charlson scores; analyzed by multiple linear regression models.
