Invited commentary: quality of care and the volume-outcome relationship--what's next for surgery?

Impact of Interfacility Transfer of Ruptured Abdominal Aortic Aneurysm Patients

OBJECTIVES

Interfacility transfer (IT) of patients with ruptured (r) abdominal aortic aneurysm (AAA) occurs not infrequently for a higher level of care. This study evaluates using contemporary administrative database the impact of IT on mortality after rAAA repair.

METHODS

Healthcare Cost and Utilization Project Database for NY (2016) and NJ/MD/FL (2016-2017) were queried using ICD-10^th edition to identify patients who underwent open and endovascular repair of AAA. Hospitals were categorized into quartiles (Q) per overall volume. Mortality rates of IT vs non-transferred (NT) rAAA patients per treatment modality (open [rOAR] vs. endovascular [rEVAR]) were compared. Cox proportional hazard model was used to estimate hazard ratios (HR) for mortality.

RESULTS

1475 patients presented with rAAA of whom 672 (45.6%) were not treated. Of the remaining 803 patients, 226 (28.1%) were transferred; 50 (22.1%) died without a repair after IT. The remaining 752 patients (176 IT + 576 NT) underwent 491 rEVARs and 261 rOARs. Baseline characteristics were similar between IT and NT patients except for higher proportion of Blacks (P=.03), lower-income families (P=.049) and rOAR (45.5% vs 31.4%, p=.001) in IT patients. Overall mortality rates were similar between NT (30.2%) and IT (27.3%, P=.46). On sub-group analysis, operative mortality rates after rEVAR were similar between NT and IT patients, without differences among hospital quartiles. After rOAR, however, operative mortality rates were lower in IT patients, largely due to improved outcomes in Q4 hospitals (P=.001, Q4 vs Q1, 2 & 3). Cox regression analysis demonstrated age (HR 1.03, CI 1.00-1.06, P=.02) and low-volume hospitals (Q1-3) (HR 1.89, CI 1.02-3.51, P=.04) are predictors of mortality. Total charges were similar ($286,727 IT vs $265,717 NT, P=.38).

CONCLUSIONS

Less than 30% of rAAA patients deemed to be a candidate for repair are transferred. IT does not affect mortality rates after rEVAR, irrespective of hospital volume. For rOAR candidates, however, regionalization of care with prompt transfer to a high-volume center improves the survival benefits without increased health care cost.

Evaluating Measures of Hospital Quality:Evidence from Ambulance Referral Patterns

Hospital quality measures are crucial to a key idea behind health care payment reforms: "paying for quality" instead of quantity. Nevertheless, such measures face major criticisms largely over the potential failure of risk adjustment to overcome endogeneity concerns when ranking hospitals. In this paper we test whether patients treated at hospitals that score higher on commonly-used quality measures have better health outcomes in terms of rehospitalization and mortality. To compare similar patients across hospitals in the same market, we exploit ambulance company preferences as an instrument for hospital choice. We find that a variety of measures used by insurers to measure provider quality are successful: choosing a high-quality hospital compared to a low-quality hospital results in 10-15% better outcomes.

Hospital and surgeon variation in positive circumferential resection margin among rectal cancer patients

BACKGROUND

The objective of this study was to evaluate variation in positive CRM at the surgeon and hospital levels and assess impact on disease-specific survival.

METHODS

Patients with stage I-III rectal cancer were identified in New York State. Bayesian hierarchical regressions estimated observed-to-expected (O/E) ratios for each surgeon/hospital. Competing-risks analyses estimated disease-specific survival among patients who were treated by surgeons/hospitals with O/E > 1 compared to those with O/E ratio ≤ 1.

RESULTS

Among 1,251 patients, 208 (17%) had a positive CRM. Of the 345 surgeons and 118 hospitals in the study, 99 (29%) and 48 (40%) treated a higher number of patients with CRM than expected, respectively. Patients treated by surgeons with O/E > 1 (HR = 1.38, 95% CI = 1.16, 1.67) and those treated at hospitals with O/E > 1 (HR = 1.44, 95% CI = 1.11, 1.85) had worse disease-specific survival.

DISCUSSION

Surgeon and hospital performance in positive CRM is associated with worse prognosis suggesting opportunities to enhance referral patterns and standardize care.

The effect of surgeon and hospital volume on mortality after open and endovascular repair of abdominal aortic aneurysms

BACKGROUND

Higher hospital and surgeon volumes are independently associated with improved mortality after open repair of abdominal aortic aneurysms (AAAs) in the era before endovascular AAA repair (EVAR). The effects of both surgeon and hospital volume on mortality after EVAR and open repair in the current era are less well defined.

METHODS

We studied Medicare beneficiaries who underwent elective AAA repair from 2001 to 2008. Volume was measured by procedure type during the 1-year period preceding each procedure and was further categorized into quintiles of volume for surgeon and hospital. Multilevel logistic regression models were used to evaluate the effect of surgeon volume, accounting for hospital volume, on mortality after adjusting for patient demographic and comorbid conditions as well as the analogous effect of hospital volume adjusting for surgeon volume. The multilevel models included random effects for surgeon and hospital to account for the clustering of multiple patients within the same surgeon and within the same hospital.

RESULTS

We studied 122,495 patients who underwent AAA repair (open: 45,451; EVAR: 77,044). After EVAR, perioperative mortality did not differ by surgeon volume (quintile 1 [0-6 EVARs]: 1.8%; quintile 5 [28-151 EVARs]: 1.6%; P = .29), but decreased with greater hospital volume (quintile 1 [0-9 EVARs]: 1.9%; quintile 5 [49-198 EVARs]: 1.4%; P < .01). After open repair, perioperative mortality decreased with both higher surgeon volume (quintile 1 [0-3 open repairs]: 6.4%; quintile 5 [14-62 open repairs]: 3.8%; P < .01) and hospital volume (quintile 1 [0-5 open repairs]: 6.3%; quintile 5 [14-62 open repairs]: 3.8%; P < .01). After adjustment for other predictors, surgeon volume was not associated with perioperative mortality after EVAR (odds ratio [OR], 0.9; 95% confidence interval [CI], 0.7-1.1); however, hospital volume was associated with higher perioperative mortality (quintile 1: OR, 1.5; 95% CI, 1.2-1.9; quintile 2: OR, 1.3; 95% CI, 1.02-1.6; and quintile 3: OR, 1.2; 95% CI, 1.01-1.5, compared with 5). After open repair, higher surgeon volume was also associated with lower mortality (quintile 1: OR, 1.5; 95% CI, 1.3-1.8; quintile 2: OR, 1.3; 95% CI, 1.1-1.6; and quintile 3: OR, 1.2; 95% CI, 1.1-1.4, compared with 5). Risk of mortality also was higher for patients treated at lower-volume hospitals (quintile 1: OR, 1.3; 95% CI, 1.1-1.5; quintile 2: OR, 1.3; 95% CI, 1.1-1.5; and quintile 3: OR, 1.2; 95% CI, 1.1-1.4, compared with 5).

CONCLUSIONS

After EVAR, hospital volume is minimally associated with perioperative mortality, with no such association for surgeon volume. After open AAA repair, surgeon and hospital volume are both strongly associated with mortality. These findings suggest that open surgery should be concentrated in hospitals and surgeons with high volume.

Case mix-adjusted cost of colectomy at low-, middle-, and high-volume academic centers

BACKGROUND

Efforts to regionalize surgery based on thresholds in procedure volume may have consequences on the cost of health care delivery. This study aims to delineate the relationship between hospital volume, case mix, and variability in the cost of operative intervention using colectomy as the model.

METHODS

All patients undergoing colectomy (n = 90,583) at 183 academic hospitals from 2009-2012 in The University HealthSystems Consortium Database were studied. Patient and procedure details were used to generate a case mix-adjusted predictive model of total direct costs. Observed to expected costs for each center were evaluated between centers based on overall procedure volume.

RESULTS

Patient and procedure characteristics were significantly different between volume tertiles. Observed costs at high-volume centers were less than at middle- and low-volume centers. According to our predictive model, high-volume centers cared for a less expensive case mix than middle- and low-volume centers ($12,786 vs $13,236 and $14,497, P < .01). Our predictive model accounted for 44% of the variation in costs. Overall efficiency (standardized observed to expected costs) was greatest at high-volume centers compared to middle- and low-volume tertiles (z score -0.16 vs 0.02 and -0.07, P < .01).

CONCLUSION

Hospital costs and cost efficiency after an elective colectomy varies significantly between centers and may be attributed partially to the patient differences at those centers. These data demonstrate that a significant proportion of the cost variation is due to a distinct case mix at low-volume centers, which may lead to perceived poor performance at these centers.

Primary Stroke Center Hospitalization for Elderly Patients With Stroke: Implications for Case Fatality and Travel Times

IMPORTANCE

Physicians often must decide whether to treat patients with acute stroke locally or refer them to a more distant Primary Stroke Center (PSC). There is little evidence on how much the increased risk of prolonged travel time offsets benefits of a specialized PSC care.

OBJECTIVES

To examine the association of case fatality with receiving care in PSCs vs other hospitals for patients with stroke and to identify whether prolonged travel time offsets the effect of PSCs.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study of Medicare beneficiaries with stroke admitted to a hospital between January 1, 2010, and December 31, 2013. Drive times were calculated based on zip code centroids and street-level road network data. We used an instrumental variable analysis based on the differential travel time to PSCs to control for unmeasured confounding. The setting was a 100% sample of Medicare fee-for-service claims.

EXPOSURES

Admission to a PSC.

MAIN OUTCOMES AND MEASURES

Seven-day and 30-day postadmission case-fatality rates.

RESULTS

Among 865 184 elderly patients with stroke (mean age, 78.9 years; 55.5% female), 53.9% were treated in PSCs. We found that admission to PSCs was associated with 1.8% (95% CI, -2.1% to -1.4%) lower 7-day and 1.8% (95% CI, -2.3% to -1.4%) lower 30-day case fatality. Fifty-six patients with stroke needed to be treated in PSCs to save one life at 30 days. Receiving treatment in PSCs was associated with a 30-day survival benefit for patients traveling less than 90 minutes, but traveling at least 90 minutes offset any benefit of PSC care.

CONCLUSIONS AND RELEVANCE

Hospitalization of patients with stroke in PSCs was associated with decreased 7-day and 30-day case fatality compared with noncertified hospitals. Traveling at least 90 minutes to receive care offset the 30-day survival benefit of PSC admission.

Risk-adjusted pathologic margin positivity rate as a quality indicator in rectal cancer surgery

PURPOSE

Margin positivity after rectal cancer resection is associated with poorer outcomes. We previously developed an instrument for calculating hospital risk-adjusted margin positivity rate (RAMP) that allows identification of performance-based outliers and may represent a rectal cancer surgery quality metric.

METHODS

This was an observational cohort study of patients with rectal cancer within the National Cancer Data Base (2003 to 2005). Hospital performance was categorized as low outlier (better than expected), high outlier (worse than expected), or non-RAMP outlier using standard observed-to-expected methodology. The association between outlier status and overall risk of death at 5 years was evaluated using Cox shared frailty modeling.

RESULTS

Among 32,354 patients with cancer (mean age, 63.8 +/-13.2 years; 56.7% male; 87.3% white) treated at 1,349 hospitals (4.9% high outlier, 0.7% low outlier), 5.6% of patients were treated at high outliers and 3.0% were treated at low outliers. Various structural (academic status and volume), process (pathologic nodal evaluation and neoadjuvant radiation therapy use), and outcome (sphincter preservation, readmission, and 30-day postoperative mortality) measures were significantly associated with outlier status. Five-year overall survival was better at low outliers (79.9%) compared with high outliers (64.9%) and nonoutliers (68.9%; log-rank test, P < .001). Risk of death was lower at low outliers compared with high outliers (hazard ratio [HR], 0.61; 95% CI, 0.50 to 0.75) and nonoutliers (HR, 0.69; 95% CI, 0.57 to 0.83). Risk of death was higher at high outliers compared with nonoutliers (HR, 1.12; 95% CI, 1.03 to 1.23).

CONCLUSION

Hospital RAMP outlier status is a rectal cancer surgery composite metric that reliably captures hospital quality across all levels of care and could be integrated into existing quality improvement initiatives for hospital performance.

Quality improvement for pancreatic cancer care: is regionalization a feasible and effective mechanism?

Variability exists in the quality of pancreatic cancer care provided in the United States. High-volume centers have been shown to have improved outcomes for pancreatectomy. Regionalization of pancreatic cancer care to high-volume centers has the potential to improve care and outcomes. Practical limitations such as overloading currently available high-volume centers, extending patient travel times, sharing patients within a multipayer health system, and incorporating patient preferences must be addressed for regionalization to become a reality. The benefits and limitations of regionalization of pancreatic cancer care are discussed in this review. To improve the overall quality of pancreatic cancer care at all hospitals in the United States, a combination of referral of patients with pancreatic cancer to high- and moderate-volume hospitals in conjunction with specific quality-improvement efforts at those institutions is proposed.

Measuring quality in health care and its implications for pay-for-performance initiatives

The quality of health care is important to American consumers, and discussion on quality will be a driving force toward improving the delivery of health care in America. Funding agencies are proposing a variety of quality measures, such as centers of excellence, pay-for-participation, and pay-for-performance initiatives, to overhaul the health care delivery system in this country. It is quite uncertain, however, whether these quality initiatives will succeed in curbing the unchecked growth in health care spending in this country, and physicians understandably are concerned about more intrusion into the practice of medicine. This article outlines the genesis of the quality movement and discusses its effect on the surgical community.

[Surgical volume. An American perspective]

Due to an increasing interest in patient safety and quality health care, many studies attempt to show a relationship between procedural volume at the institutional and individual level and patient outcome. Despite the correlation between number of surgeons and institutional volume in major operative procedures such as coronary artery bypass graft, pancreatic resection, and esophagectomy, these parameters are likely to be proxy for individual factors such as experience and structural aspects. In general the relationship between case numbers and results is more convincing in cancer surgery than for cardiovascular procedures, and risk adjustment may play an important role for interpreting results of the various studies. Exact thresholds cannot be determined and thus remain speculative. It appears difficult to implement practical changes based on the observations, because the etiology and causality of the relationship between volume and outcome are still not understood. The simple focus on volume does not apply to measurements of quality but can be a starting point for further studies to identify more specific factors associated with surgical quality.

The Clinical Outcomes Assessment Toolkit: a framework to support automated clinical records-based outcomes assessment and performance measurement research

The Clinical Outcomes Assessment Toolkit (COAT) was created through a collaboration between the University of California, Los Angeles and Brigham and Women's Hospital to address the challenge of gathering, formatting, and abstracting data for clinical outcomes and performance measurement research. COAT provides a framework for the development of information pipelines to transform clinical data from its original structured, semi-structured, and unstructured forms to a standardized format amenable to statistical analysis. This system includes a collection of clinical data structures, reusable utilities for information analysis and transformation, and a graphical user interface through which pipelines can be controlled and their results audited by nontechnical users. The COAT architecture is presented, as well as two case studies of current implementations in the domain of prostate cancer outcomes assessment.

Shaping the future of surgery: the role of private regulation in determining quality standards

OBJECTIVE

To educate surgeons about the growth of the private regulatory movement and its potential implications for the practice of surgery.

METHODS

An in-depth analysis and literature review of one of the largest private regulatory groups, the Leapfrog Group, provides a model for understanding the impact of these groups on the practice of surgery. A detailed discussion of the history, mission, structure, and quality initiatives of Leapfrog is included.

RESULTS

Private regulatory groups are using quality standards as a method for controlling the rising cost of health care. Traditionally, little financial support, manpower, or incentives have existed for individual surgeons and hospitals to report and maintain their own outcomes data. However, as surgical outcomes have increasingly become the target of quality improvement initiatives, the need to measure performance is gaining importance. Surgical quality has been both a direct target of private regulation, as illustrated by the evidence-based hospital referral guidelines of Leapfrog, and an indirect target with initiatives like computerized physician order entry and ICU staffing guidelines.

CONCLUSIONS

Private regulation is rapidly reshaping the way we practice and teach surgery. It is almost a certainty that their power, popularity, financial support, and missions will all continue to expand. As surgeons, we must decide soon if we wish to be an active participant in shaping the movement or, rather, if we are going to let it shape us by remaining largely uninvolved.

The volume-outcome relationship: don't believe everything you see

This paper investigates methodological limitations of the volume-outcome relationship. A brief overview of quality measurement is followed by a discussion of two important aspects of the relationship.

Is Hospital Procedure Volume a Reliable Marker of Quality for Coronary Artery Bypass Surgery? A Comparison of Risk and Propensity Adjusted Operative and Midterm Outcomes

BACKGROUND

Worse operative mortality has been reported for hospitals with low versus high coronary artery bypass grafting surgery volumes. Despite a lack of comparisons beyond the early postoperative period and evidence of surgeon-volume confounding, some have suggested that regionalization of coronary artery bypass grafting in favor of high volume institutions is warranted.

METHODS

We retrospectively compared operative mortality and 3-year survival in coronary artery bypass grafting patients (2001 to 2003) at a low-volume hospital (n = 504; 160 per year [median]) versus a high-volume hospital (n = 1,410; 487 per year) served by the same high-volume surgeon team. Covariate risk adjustment was done via multivariate and propensity modeling.

RESULTS

The two hospital cohorts exhibited multiple demographic and risk factor differences. Unadjusted low-volume hospital vs high-volume hospital operative mortality was similar overall (2.38% vs 2.98%; p = 0.59) with nearly identical Society of Thoracic Surgeons observed-to-expected ratios (0.83 vs 0.82), irrespective of preoperative risk category. Hospital volume did not predict operative mortality (odds ratio, 95% confidence interval = 0.82; p = 0.602). At follow-up, a total of 28 low-volume hospital deaths (5.6%) and 135 high-volume hospital deaths (9.6%) occurred at similar surgery-to-death intervals (p = 0.7). Unadjusted 0 to 3-year survival was significantly worse for high-volume hospitals (risk ratio = 1.59; 1.06 to 2.39; p = 0.026). Yet procedure volume was not independently associated with worse midterm survival after covariate (risk ratio = 1.28; 0.84 to 1.96; p = 0.247) or propensity score (risk ratio = 1.11; 0.72 to 1.71; p = 0.648) adjustment.

CONCLUSIONS

Hospital and surgeon volume effects on coronary artery bypass grafting outcomes are interdependent, and therefore hospital coronary artery bypass grafting volume per se is not a reliable marker of quality. Instead, outcome quality markers should rely on thorough risk-adjustment based on detailed clinical databases, possibly including annual and cumulative surgeon volume.

Early efficacy of CABG care delivery in a low procedure-volume community hospital: operative and midterm results

Background

The Leapfrog Group recommended that coronary artery bypass grafting (CABG) surgery should be done at high volume hospitals (>450 per year) without corresponding surgeon-volume criteria. The latter confounds procedure-volume effects substantially, and it is suggested that high surgeon-volume (>125 per year) rather than hospital-volume may be a more appropriate indicator of CABG quality.

Methods

We assessed 3-year isolated CABG morbidity and mortality outcomes at a low-volume hospital (LVH: 504 cases) and compared them to the corresponding Society of Thoracic Surgeons (STS) national data over the same period (2001–2003). All CABGs were performed by 5 high-volume surgeons (161–285 per year). "Best practice" care at LVH – including effective practice guidelines, protocols, data acquisition capabilities, case review process, dedicated facilities and support personnel – were closely modeled after a high-volume hospital served by the same surgeon-team.

Results

Operative mortality was similar for LVH and STS (OM: 2.38% vs. 2.53%), and the corresponding LVH observed-to-expected mortality (O/E = 0.81) indicated good quality relative to the STS risk model (O/E<1). Also, these results were consistent irrespective of risk category: O/E was 0, 0.9 and 1.03 for very-low risk (<1%), low risk (1–3%) and moderate-to-high risk category (>3%), respectively. Postoperative leg wound infections, ventilator hours, renal dysfunction (no dialysis), and atrial fibrillation were higher for LVH, but hospital stay was not. The unadjusted Kaplan-Meier survival for the LVH cohort was 96%, 94%, and 92% at one, two, and three years, respectively.

Conclusion

Our results demonstrated that high quality CABG care can be achieved at LVH programs if 1) served by high volume surgeons and 2) patient care procedures similar to those of large programs are implemented. This approach may prove a useful paradigm to ensure high quality CABG care and early efficacy at low volume institutions that wish to comply with the Leapfrog standards.

The Leapfrog Initiative: a potential threat to surgical education

PURPOSE

The Leapfrog Initiative was established in January 2000 by the Business Roundtable (BRT) in response to the Institute of Medicine report on quality and safety of medical care. The BRT is composed of chief executive officers of U.S. corporations representing more than 28 million employees. Leapfrog has proposed 3 hospital safety measures-computerized physician order entry, intensive care unit physician staffing standards and evidence-based hospital referral, which states that hospitals must meet certain volume/year criteria. Three of these criteria are pertinent to general surgery. They are abdominal aortic aneurysm (AAA) repair greater than or equal to 30/year, carotid endarterectomy (CE) greater than or equal to 100/year, and esophageal cancer surgery (ECS) greater than or equal to 7/year. Hospitals failing to meet these requirements would not be eligible to treat patients employed by BRT corporations.

METHODS

Data were obtained from the Residency Review Committee (RRC) for Surgery Resident Statistics Summary for 1999 to 2001. Comparisons were made between the numbers of the Leapfrog index cases required and the actual number of cases performed by each graduating chief resident. Data from the Connecticut Hospital Association (CHA) for fiscal year 2000 were also analyzed. Outcomes for procedures at The Stamford Hospital were reviewed.

RESULTS

Data obtained from the RRC reveal that the mode numbers for each of the 3 evidence-based standards for each graduating chief resident in 2000 and 2001 are 5 and 3 for AAA, 15 and 17 for CE, and 0 in both years for ECS. Extrapolation using the mode for each procedure reveals that hospitals with 5 or 6 graduating chief residents may be ineligible to treat patients for AAA and CE. Hospitals with less than or equal to 5 chief residents would be excluded from performing CE. Very few institutions are performing adequate numbers of ECS. Only 4 of 31 CT hospitals would be allowed to perform AAA, and only 3 of 31 could perform CE. Only 1 Connecticut hospital performed more than 7 ECS cases in FY 2000. It is apparent that Leapfrog standards will have serious economic impact on many hospitals, as well as displacing patients to other cities for care.

CONCLUSIONS

Surgical chairs and program directors should be aware of the Leapfrog standards and assess their own programs and institutions for compliance. Performance improvement and outcomes data for all evidence-based standards should be reviewed.

Does pediatric surgical specialty training affect outcome after Ramstedt pyloromyotomy? A population-based study

OBJECTIVE

Ramstedt pyloromyotomy is a common operation in infants and is often done by general surgeons. We wished to determine whether there are any differences in outcome when this procedure is done by subspecialist pediatric general surgeons as compared with general surgeons.

METHODS

All Ramstedt pyloromyotomies in the province of Ontario between 1993 and 2000 were reviewed. Children with complex medical conditions or prematurity were excluded. Cases done by general surgeons were compared with those done by pediatric surgeons, specifically examining hospital stay and complications.

RESULTS

Of 1777 eligible infants, 67.9% were operated on by pediatric surgeons and 32.1% by general surgeons. Total and postoperative lengths of stay were longer in the general surgeon group compared with the pediatric surgeons (4.31 vs 3.50 days for length of stay; 2.95 vs 2.25 days for postoperative length of stay). The general surgeons had a higher overall complication rate (4.18% vs 2.58%). The incidence of duodenal perforation among general surgeons was almost 4 times that of pediatric surgeons (relative risk: 3.65; 95% confidence interval: 1.43-9.32). Of the 4 infants who required repeat surgery because of an incomplete pyloromyotomy, all were originally operated on by a general surgeon. Analysis of the effect of surgeon volume on outcomes suggested that higher volume resulted in better outcome in both groups.

CONCLUSION

Subspecialist pediatric general surgeons achieve superior outcomes for children who undergo Ramstedt pyloromyotomy.

The Leapfrog volume criteria may fall short in identifying high-quality surgical centers

OBJECTIVE

The original Leapfrog Initiative recommends selective referral based on procedural volume thresholds (500 coronary artery bypass graft [CABG] surgeries, 30 abdominal aortic aneurysm [AAA] repairs, 100 carotid endarterectomies [CEA], and 7 esophagectomies annually). We tested the volume-mortality relationship for these procedures in the University HealthSystem Consortium (UHC) Clinical DatabaseSM, a database of all payor discharge abstracts from UHC academic medical center members and affiliates. We determined whether the Leapfrog thresholds represent the optimal cutoffs to discriminate between high- and low-mortality hospitals.

METHODS

Logistic regression was used to test whether volume was a significant predictor of mortality. Volume was analyzed in 3 different ways: as a continuous variable, a dichotomous variable (above and below the Leapfrog threshold), and a categorical variable. We examined all possible thresholds for volume and observed the optimal thresholds at which the odds ratio is the highest, representing the greatest difference in odds of death between the 2 groups of hospitals.

RESULTS

In multivariate analysis, a relationship between volume and mortality exists for AAA in all 3 models. For CABG, there is a strong relationship when volume is tested as a dichotomous or categorical variable. For CEA and esophagectomy, we were unable to identify a consistent relationship between volume and outcome. We identified empirical thresholds of 250 CABG, 15 AAA, and 22 esophagectomies, but were unable to find a meaningful threshold for CEA.

CONCLUSIONS

In this group of academic medical centers and their affiliated hospitals, we demonstrated a significant relationship between volume and mortality for CABG and AAA but not for CEA and esophagectomy, based on the Leapfrog thresholds. We described a new methodology to identify optimal data-based volume thresholds that may serve as a more rational basis for selective referral.

The Leapfrog standards: ready to jump from marketplace to courtroom?

The Leapfrog Group, a consortium of large employers, aims to use its collective purchasing power to motivate hospitals to implement particular measures designed to improve patient safety and the quality of care. While these criteria are meant to be purely aspirational, and while Leapfrog's effort is praiseworthy, we caution that the articulation of these standards of care may have unintended legal consequences. Efforts by aggressive medical malpractice attorneys could rapidly transform Leapfrog's standards from marketplace advantages for compliant hospitals to performance expectations required by law. This undesirable potential outcome compounds the importance of selecting these standards with the utmost care.

The volume-outcome relationship: from Luft to Leapfrog

Numerous reports have documented a volume-outcome relationship for complex medical and surgical care, although many such studies are compromised by the use of discharge abstract data, inadequate risk adjustment, and problematic statistical methodology. Because of the volume-outcome association, and because valid outcome measurements are unavailable for many procedures, volume-based referral strategies have been advocated as an alternative approach to health-care quality improvement. This is most appropriate for procedures with the greatest outcome variability between low-volume and high-volume providers, such as esophagectomy and pancreatectomy, and for particularly high-risk subgroups of patients. Whenever possible, risk-adjusted outcome data should supplement or supplant volume standards, and continuous quality improvement programs should seek to emulate the processes of high-volume, high-quality providers. The Leapfrog Group has established a minimum volume requirement of 500 procedures for coronary artery bypass grafting. In view of the questionable basis for this recommendation, we suggest that it be reevaluated.

Should volume standards for cardiovascular surgery focus only on high-risk patients?

BACKGROUND

Payers and policy makers are attempting to concentrate selected cardiovascular procedures in high-volume centers. A recent analysis of coronary artery bypass grafting (CABG), however, suggests that volume-based referral initiatives should focus only on high-risk patients.

METHODS AND RESULTS

Using the national Medicare database (1994 to 1999), we studied the operative mortality in patients undergoing 4 cardiovascular procedures (CABG, aortic valve replacement, mitral valve replacement, and elective abdominal aortic aneurysm repair). We defined 2 categories of patient risk: high-risk (patients in the highest 25th percentile of predicted risk on the basis of a logistic regression model) and low-risk (patients in the lowest 75th percentile). We then compared operative mortality in patients undergoing surgery at very-high volume hospitals (VHVH, highest 20th percentile of procedure volume) and very-low volume hospitals (VLVH, lowest 20th percentile of procedure volume). Absolute differences in operative mortality between VLVH and VHVH were somewhat larger in high-risk patients. However, volume-related differences in mortality were also significant for low-risk patients undergoing one of the 4 procedures. In relative terms, the effect of hospital volume was similar in both high- and low-risk patients. For high- and low-risk patients, the relative risk (RR) of mortality between VHVH and VLVH were nearly equal for CABG (RR=0.78 for low-risk patients, RR=0.77 for high risk patients), aortic valve replacement (0.73 versus 0.76), mitral valve replacement (0.73 versus 0.74), and abdominal aortic aneurysm repair (0.51 versus 0.54).

CONCLUSIONS

Although the merits of volume-based referral initiatives can be debated on many grounds, there seems to be little rationale for restricting these initiatives to high-risk patients.

[Relation between activity volume and surgeon's results: myth or reality?]

The relationship between volume and surgical outcome seems logical, but needs to be demonstrated in the real world. A qualitative systematic review has been conducted to verify this hypothesis. Five systematic reviews and hundred original papers have been retrieved and analysed. Most of the studies were retrospective and used administrative data instead of medical charts. Moreover few studies involved a good case mix adjustment when comparing surgical units or individual surgeons. These methodological flaws do not allow any evidence based conclusions. Even though a positive relationship is suggested for surgical units, the relationship between volume and outcome was however less obvious for an individual surgeon. There is some evidence that the relationship varied greatly according to the specialty or the procedure evaluated. A new approach based on predictive scores comparing expected versus observed outcomes is mandatory and seems to be the best way to assess objectively the relationship between surgical volume and outcomes.