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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptNIH Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
 
J Urol. Author manuscript; available in PMC Jul 1, 2013.
Published in final edited form as:
PMCID: PMC3697119
NIHMSID: NIHMS474291
Surgical Quality among Medicare Beneficiaries Undergoing Outpatient Urologic Surgery
John M. Hollingsworth, MD, MS,1,2 Chris S. Saigal, MD, MPH,3,4 Julie C. Lai, MPH,4 Rodney L. Dunn, MS,1,2 Seth A. Strope, MD, MPH,5 Brent K. Hollenbeck, MD, MS,1,2 and the Urologic Diseases in America Project
1University of Michigan, Department of Urology, Dow Division of Health Services Research
2University of Michigan, Center for Healthcare Outcomes & Policy
3University of California at Los Angeles, Department of Urology
4RAND Corporation, Santa Monica, California
5Washington University, Division of Urology Surgery
Address correspondence to: Brent K. Hollenbeck, MD, MS, Associate Professor of Urology, North Campus Research Complex, 2800 Plymouth Road, Bldg 520, 3rd Floor, #3143, Ann Arbor, MI 48109-2800, Tel: 734-936-0054, Fax: 734-232-2400, bhollen/at/med.umich.edu
Introduction and objective
The cost-efficiency gains achieved from moving procedures to ASCs and the office may be mitigated if the quality of surgical care at these facilities is not comparable to that of the hospital. Motivated by this, we assessed short-term morbidity and mortality for patients by location of care.
Methods
Using a national sample of Medicare claims (1998 – 2006), we identified elderly beneficiaries who underwent one of 22 common outpatient urologic procedures. After determining the facility type at which each procedure was performed, we then measured 30-day mortality, unexpected admissions, and postoperative complications. Finally, we fit multivariable logistic regression models to evaluate the association between occurrence of an adverse event and the ambulatory setting where surgical care was delivered.
Results
Over the study period, there was a substantial increase in the frequency of nonhospital-based outpatient surgery. Compared to ASCs and the office, hospitals treated more women (P<0.001). Their patients also tended to be less healthy (P<0.001). While patients experienced fewer postoperative complications following surgery at an ASC, procedures performed outside the hospital were associated with a higher likelihood of a same-day admission [ASC: OR, 6.96 (95% CI, 4.44 – 10.90); office: OR, 3.64 (95% CI, 2.48 – 5.36)]. However, it is important to note that, with case-mix adjustment, the probability of any adverse event was exceedingly low across all ambulatory settings.
Conclusions
These data indicate that small, but measurable variation in surgical quality exists by location of care delivery.
Of the 72 million surgical procedures performed annually in the United States, over 70% occur in an outpatient setting.1 Although most occur in hospital outpatient departments,2 improved technology and anesthesia have facilitated movement of many procedures away from the more expensive hospital environment to other outpatient facilities, including freestanding ASCs and the office. In 2009 alone, nearly 16 million surgical procedures were performed at these facilities.3, 4 While the trend towards delivery of surgical care in less resource-intensive practice settings may be associated with economic advantages, effects of this migration on surgical quality are uncertain.
In fact, there are at least two reasons to believe that surgical quality may vary by location of care. On one hand, hospitals have access to more organizational resources (e.g., intensive care services and the ability to immediately transfer patients to other clinical departments) than other outpatient facilities,5 which may help their performance. On the other hand, ASCs and the office tend to have a “limited-service” focus and are more likely than hospitals to specialize on certain types of procedures.6 Insofar as this specialization allows them to secure high procedural volumes, ASCs and the office may enjoy improved outcomes.7, 8
To better understand the influence of location of care on surgical quality, we used national Medicare claims to examine risk-adjusted morbidity and mortality among patients undergoing common outpatient urologic procedures performed in hospitals, ASCs, and the office. The findings reported herein serve to inform policymakers and payers on the appropriateness of movement of patients and procedures from the more expensive hospital setting to lower-intensity outpatient facilities.
Subjects and databases
For our study, we analyzed a 5% national sample of Medicare beneficiaries (1998 – 2006). Using HCPCS codes, we identified patients 65 years and older with continuous enrollment in Medicare parts A and B who underwent endoscopic bladder, urethral, or ureteral surgery; microwave therapy for prostate enlargement; prostate biopsy; shockwave lithotripsy; urethral dilation; or urodynamic procedures (Appendix Table 1). We focused on these procedures for two reasons. Our preliminary analysis indicates that these procedures account for nearly 95% of all ambulatory urologic procedures. Furthermore, these procedures can be performed in each of the surgical locations of interest (i.e., hospitals, ASCs, and the office. Because services provided to Medicare Advantage patients are not consistently captured in claims files, we excluded these patients from our study.
Next, we developed a three-level categorical variable, specifying the location of care: (i.e., hospital, ASC, or office), using appropriate Place of Service codes from Medicare’s carrier file. We then determined the date of surgery from the surgeon’s claim. We considered each procedure as an independent event such that it was possible for some patients to have more than one procedure in our analysis.
Measures of surgical quality
From the Medicare files, we assessed rates of operative mortality, hospital admission, and postoperative complications. We defined operative mortality as death occurring within 30 days of surgery or death during hospitalization that began within 30 days of surgery.9 To determine rates of unexpected hospitalization, we considered both same-day admission (i.e., on the day of the procedure) and subsequent admission within 30 days of the procedure.10 We identified 30-day postoperative complications using ICD-9 CM diagnosis codes (Appendix Table 2).11
Statistical Analysis
For our initial analytic step, we examined the distribution of procedures across outpatient surgery settings and how it changed over the study period. We then made comparisons between patients based on the location where their procedure was performed. In particular, we examined differences between patients with respect to their age, gender, race (white, black, or other), comorbid status (assessed using an adaptation of the Charlson index12), and area of residence (Northeast, Midwest, South, or West), using appropriate parametric and nonparametric statistics.
Finally, we evaluated the relationship between surgical quality and the location where care was delivered. With the patient serving as our unit of analysis, we fit a series of multivariable logistic regression models for each of our binary outcomes. We accounted for case- mix differences, adjusting our models for those patient characteristics described above. Given the potential correlation of observations (i.e., multiple observations on the same subject and patients clustered within facilities), we used robust variance estimators.13 We used our full models to produce predicted probabilities of each adverse event.
We carried out all analyses using the SAS statistical package (SAS, version 9.1; SAS Institute, Cary, NC). All tests were two-tailed, and we set the probability of Type 1 error at 0.05. The Institutional Review Boards of the University of California at Los Angeles and the University of Michigan approved our study.
Over the study period, surgical activity at ASCs and the office increased for nearly every procedure with a concomitant decline in hospital utilization. For instance, the frequency of ASC- and office-based endoscopic bladder surgery rose from 4.5% and 81.7% in 1998 to 8.2% and 85.1%, respectively, in 2006 (Figure 1). The one exception to this trend was shockwave lithotripsy, where procedure rates at each care setting remained relatively flat.
Figure 1
Figure 1
Distribution of selected urologic procedures across ambulatory surgery settings over the study period.
There were significant differences between patients with respect to their gender, race, level of comorbidity, and area of residence when stratified by outpatient surgery setting (Table 1). Specifically, women and black patients were less likely than men and white patients, respectively, to be treated at an ASC or in the office (P<0.001 for each comparison). In addition, lower acuity cases were concentrated at nonhospital facilities. For instance, the proportion of patients with a Charlson score of “0” was 59.1% at hospitals versus 82.6% and 62.9% at ASCs and in the office, respectively (P<0.001). There were also significantly more ambulatory surgery visits to ASCs and the office among patients who resided in the South (P<0.001).
Table 1
Table 1
Differences in case mix across ambulatory care settings.
On multivariable regression, male gender, increasing age, and level of comorbidity were associated with higher odds of an adverse event (Table 2). Compared with hospitals, rates of postoperative complication were significantly lower at ASCs (Table 2). However, procedures performed outside the hospital were associated with a higher likelihood of a same-day admission [ASC: OR, 6.96 (95% CI, 4.44 – 10.90); office: OR, 3.64 (95% CI, 2.48 – 5.36)]. After adjusting for case mix differences, the probability of an adverse event was low across all ambulatory surgery settings (Figure 2).
Table 2
Table 2
Adjusted odds of an adverse event following outpatient surgery.
Figure 2
Figure 2
Predicted probability of an adverse event following surgery, stratified by ambulatory setting.
Our findings highlight a national trend toward increased use of lower-intensity ambulatory settings for several common outpatient urologic procedures. Outcomes varied significantly by location of care with ASCs outperforming hospitals on one dimension of surgical quality—a difference likely related to favorable patient selection. While hospital-based surgery was associated with a lower rate of same-day admission, it is important to note that the probability of any adverse event was exceedingly low, regardless of location of care.
To date, much of the literature on ambulatory surgical care in nonhospital-based facilities has focused on the issue of physician ownership and overuse.14, 15 Little empirical work has assessed the relationship between surgical quality and the setting for ambulatory surgery. Our results are concordant with prior research, showing ASCs and hospitals to have similar risk-adjusted postoperative mortality.5 However, unlike Vila and colleagues,16 we found death rates at ASCs and the office to be both low and comparable. This finding may relate, in part, to increased state-level regulation of office-based surgery.17
We also observed more frequent same-day admissions following outpatient surgery in ASCs versus hospitals. This observation contrasts with that from a previous Medicare analysis.18 It may be a reflection of the limited organizational resources at ASCs. For instance, a cautious urologist could exercise clinical judgment and admit a less healthy patient following an ASC-based surgery because the hospital would be better equipped to handle problems if they occurred. Alternatively, it may reflect decreased staffing hours at ASCs or efficiency priorities, whereby urologists at these facilities have a lower threshold to admit patients in order to maximize throughput rather than holding on to them in the post-anesthesia care unit.
Our study has several limitations that merit further discussion. First, there is clear selection bias in our study population. While we attempted to adjust for differences in case mixes between hospitals, ASCs, and the office, it is entirely possible that urologists recommend certain settings based on information that is not readily available in billing claims. Second, we used HCPCS codes to identify procedures of interest. Medical coding, which is intended for billing and reimbursement, may not accurately reflect how complex a surgery was. To the extent that significant heterogeneity in procedure complexity exists within a given procedure code, this could also account for quality differences across locations of care. Third, we used Medicare claims exclusively for our analysis, and our findings may not be generalizable to nonelderly Americans.
Limitations notwithstanding, our study has both clinical and policy implications. From a clinical perspective, these data highlight the need to consider a patient’s age and level of comorbidity when planning an outpatient procedure. As expected, we observed that older patients and those with more comorbid illnesses had higher odds of an adverse event. Being able to identify subgroups of patients at risk for an adverse event following ambulatory surgery will allow for more effective targeting of care delivery. From a policy perspective, large payers, like Medicare, may use our data to inform their payment systems for providers. For instance, they might consider directing patients to certain nonhospital-based facilities given the comparable quality that they provide.
Conclusions
In summary, we observed variation in surgical outcomes by location of care. However, adverse events following outpatient urologic surgery are exceedingly rare, regardless of location of care. Additional studies are needed to determine how episode costs vary across hospitals, ASCs, and the office. Insofar as ASCs and the office are more convenient for patients and/or increase surgeon productivity, these facilities may provide higher value care.
Acknowledgments
Funding: This project was supported, in part, by grant number R01HS018726 from the Agency for Healthcare Research and Quality. The content is solely the responsibility of the authors and does not necessarily represent the official views of the Agency for Healthcare Research and Quality.
 
Appendix Table 1
Identifying the study population.
Procedure TypeHCPCSDescription

Endoscopic bladder surgery51700Bladder irrigation, simple, lavage and/or instillation
52000Cystourethroscopy (separate procedure)
52310Cystourethroscopy, with removal of foreign body, calculus, or ureteral stent from urethra or bladder (separate procedure); simple
52204Cystourethroscopy, with biopsy
52214Cystourethroscopy, with fulguration (including cryosurgery or laser surgery) of trigone, bladder neck, prostatic fossa, urethra, or periurethral glands
52224Cystourethroscopy, with fulguration (including cryosurgery or laser surgery) or treatment of MINOR (less than 0.5 cm) lesion(s) with or without biopsy
52234Cystourethroscopy, with fulguration (including cryosurgery or laser surgery) and/or resection of; SMALL bladder tumor(s) (0.5 to 2.0 cm)

Endoscopic urethral surgery51715Endoscopic injection of implant material into the submucosal tissues of the urethra and/or bladder neck
52281Cystourethroscopy, with calibration and/or dilation of urethral stricture or stenosis, with or without meatotomy, with or without injection procedure for cystography, male or female

Endoscopic ureteral surgery52005Cystourethroscopy, with ureteral catheterization, with or without irrigation, instillation, or ureteropyelography, exclusive of radiologic service
52332Cystourethroscopy, with insertion of indwelling ureteral stent

Microwave therapy53850Transurethral destruction of prostate tissue; by microwave therapy

Prostate biopsy55700Biopsy, prostate; needle or punch, single or multiple, any approach
55859Transperineal placement of needles or catheters into prostate for interstitial radioelement application, with or without cystoscopy

Shockwave lithotripsy50590Lithotripsy, extracorporeal shock wave

Urethral dilation53600Dilation of urethral stricture by passage of sound or urethral dilator, male; initial
53660Dilation of female urethra including suppository and/or instillation; initial

Urodynamics procedures51725Simple cystometrogram
51726Complex cystometrogram
51741Complex uroflowmetry
51784Electromyography studies of anal or urethral sphincter, other than needle, any technique
51795Voiding pressure studies; bladder voiding pressure, any technique
Abbreviation: HCPCS, Healthcare Common Procedure Coding System.
Appendix Table 2
Identifying postoperative complications.
ICD-9 CodeDescription of Complication
415.11Iatrogenic pulmonary embolism and infarction
458.2Iatrogenic hypotension
512.1Iatrogenic pneumothorax
518.5Pulmonary insufficiency following trauma and surgery
598.2Postoperative urethral stricture
995.0Other anaphylactic shock
995.4Shock due to anesthesia
997.00Nervous system complications
997.01Central nervous system complication
997.02Iatrogenic cerebrovascular infarction or hemorrhage
997.09Other nervous system complications
997.1xCardiac complications
997.2xPeripheral vascular complications
997.3xRespiratory complications
997.4xDigestive complications
997.5xUrinary complications
997.61Neuroma of amputation stump
997.62Infection (chronic)
997.69Other
997.79Vascular complications of other vessels
997.9xComplications affecting other specified body systems, not elsewhere classified
997.91Hypertension
997.99Other
998.0Postoperative shock
998.00Postoperative shock
998.1Hemorrhage or hematoma or seroma complicating a procedure
998.10Hemorrhage or hematoma or seroma complicating a procedure
998.11Hemorrhage complicating a procedure
998.12Hematoma complicating a procedure
998.13Seroma complicating a procedure
998.2xAccidental puncture or laceration during a procedure
998.3xDisruption of operative wound
998.4Foreign body accidentally left during a procedure
998.5xPostoperative infection
998.6xPersistent postoperative fistula
998.7Acute reaction to foreign substance accidentally left during a procedure
998.80Other specified complications of procedures, not elsewhere classified
998.81Emphysema (subcutaneous)(surgical) resulting from a procedure
998.83Non-healing surgical wound
998.89Other specified complications
998.9Unspecified complication of procedure, not elsewhere classified
999.1Air embolism
999.2xOther vascular complications
999.3xOther infection
999.5Other serum reaction
999.7Rh incompatibility reaction
999.8Other transfusion reaction
999.9Other and unspecified complications of medical care, not elsewhere classified
Abbreviation: International Classification of Diseases, 9th Revision, Clinical Modification.
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