Surgeon Volume and Operative Mortality in the United States
John D. Birkmeyer, M.D., Therese A. Stukel, Ph.D., Andrea E. Siewers, M.P.H., Philip P. Goodney, M.D., David E. Wennberg, M.D., M.P.H., and F. Lee Lucas, Ph.D.
Background Although the relation between hospital volume andsurgical mortality is well established, for most procedures,the relative importance of the experience of the operating surgeonis uncertain.
Methods Using information from the national Medicare claimsdata base for 1998 through 1999, we examined mortality amongall 474,108 patients who underwent one of eight cardiovascularprocedures or cancer resections. Using nested regression models,we examined the relations between operative mortality and surgeonvolume and hospital volume (each in terms of total proceduresperformed per year), with adjustment for characteristics ofthe patients and other characteristics of the providers.
Results Surgeon volume was inversely related to operative mortalityfor all eight procedures (P=0.003 for lung resection, P<0.001for all other procedures). The adjusted odds ratio for operativedeath (for patients with a low-volume surgeon vs. those witha high-volume surgeon) varied widely according to the procedure— from 1.24 for lung resection to 3.61 for pancreaticresection. Surgeon volume accounted for a large proportion ofthe apparent effect of the hospital volume, to an extent thatvaried according to the procedure: it accounted for 100 percentof the effect for aortic-valve replacement, 57 percent for electiverepair of an abdominal aortic aneurysm, 55 percent for pancreaticresection, 49 percent for coronary-artery bypass grafting, 46percent for esophagectomy, 39 percent for cystectomy, and 24percent for lung resection. For most procedures, the mortalityrate was higher among patients of low-volume surgeons than amongthose of high-volume surgeons, regardless of the surgical volumeof the hospital in which they practiced.
Conclusions For many procedures, the observed associations betweenhospital volume and operative mortality are largely mediatedby surgeon volume. Patients can often improve their chancesof survival substantially, even at high-volume hospitals, byselecting surgeons who perform the operations frequently.
For many surgical procedures, patients at hospitals where ahigh number of such procedures are performed (high-volume hospitals)have lower mortality rates than those at hospitals that areless experienced with the procedures.1,2,3,4 In one recent studyof the national population of Medicare recipients, we foundstrong relations between hospital volume and operative mortalityassociated with 14 high-risk cancer resections and cardiovascularprocedures.5 Despite the considerable body of research in thisarea, little is known about the mechanisms underlying the observedassociations between volume and outcome. Because they tend tobe much larger facilities, high-volume hospitals have a broaderrange of specialist and technology-based services, better-staffedintensive care units, and other resources that are not availableat smaller centers. By virtue of these resources, high-volumehospitals may be better equipped to deliver the complex perioperativecare required by patients who are undergoing high-risk surgery.
On the other hand, the outcome of a surgical procedure may dependas much on how well the operation itself is performed as onthe resources available at the hospital. If so, another explanationfor the observed relation between the hospital volume and theoutcome may be that high-volume hospitals tend to have surgeonswho are more experienced with specific procedures. Numerousstudies have explored the associations between surgeon volume(the number of procedures performed by the surgeon) and mortalityfor some procedures.1,6,7,8,9,10,11,12 However, relatively fewof these analyses have simultaneously accounted for hospitalvolume and other potential confounding characteristics of thehospital that may be strongly correlated with surgeon volume.Moreover, few have been large enough to characterize the relativeinfluence of these two measures of volume with sufficient precision.
To address these issues, we undertook a comprehensive evaluationof the operative risk associated with eight different cardiovascularprocedures and cancer resections using data from the nationalpopulation of Medicare recipients. We had two primary aims:to assess the association between surgeon volume and operativemortality for various procedures and to achieve a better understandingof the extent to which the observed effects of hospital volumecan be explained by the experience of the operating surgeon.
Methods
Patients and Data Bases
We obtained 100 percent of the national analytic files fromthe Center for Medicare and Medicaid Services for 1998 and 1999.The Medicare Provider Analysis and Review (MEDPAR) and inpatientfiles, which contain hospital-discharge abstracts for the fee-for-service,acute care hospitalizations of all Medicare recipients, wereused to create our main data sets for analysis; the Medicaredenominator file was used to determine the vital status of thepatients. The institutional review board of Dartmouth MedicalSchool approved the study protocol.
As in our previous work,5,13,14 we used the appropriate procedurecodes from the International Classification of Diseases, NinthRevision (ICD-9), to identify all patients between 65 and 99years of age who underwent 1 of 14 cardiovascular proceduresor cancer resections. To simplify the presentation of our results,however, we present here the analyses for only four cardiovascularprocedures and four cancer resections. These procedures, whichwere selected prospectively, included two that are frequentlythe focus of debate concerning the regionalization of healthcare services (coronary-artery bypass grafting and carotid endarterectomy).Six other procedures (aortic-valve replacement, elective repairof an abdominal aortic aneurysm, pancreatic resection, esophagectomy,lung resection, and cystectomy) for which we have previouslyfound a relatively strong association between hospital volumeand operative mortality were selected to represent diverse surgicalsubspecialties.
In examining the data related to the cancer resections, we excludedfrom the analysis of outcomes (but not from the tallies of volume)patients who did not have an accompanying diagnosis code forcancer. This restriction was intended to exclude small subgroupsof patients who had a much higher level of risk at base line(e.g., patients who underwent pancreatic resection because ofinfection) and thus to minimize confounding. Similarly, patientswho underwent repair of an abdominal aortic aneurysm were excludedif they had diagnosis or procedure codes suggesting the ruptureof an aneurysm, the presence of a thoracoabdominal aneurysm,or both. We excluded from the analysis of the cohort that underwentcoronary-artery bypass grafting patients who had a valve replacedsimultaneously.
Identification of Surgeons
For all procedures, we identified the operating surgeon withthe use of the unique provider identification number listedin the "primary operator" field of the inpatient file. Previouswork has suggested the reliability of this approach in identifyingoperating surgeons.15 Records containing invalid provider identificationnumbers (6 percent) were excluded from further analysis. Forsome procedures, the number of unique, valid identificationnumbers exceeded the number of surgeons in the relevant specialtiesin the United States. This problem was most apparent in theanalysis of the two cardiac procedures, for which cardiologistswere often identified in the primary-operator field. For thisreason, we used information from the 1998 Medicare providerfiles to restrict our analysis to physicians who had designatedthemselves as surgeons. For coronary-artery bypass graftingand valve-replacement procedures, we included only self-designatedcardiothoracic surgeons. Because the specialists who performthe other procedures are more diverse, we included any self-designatedsurgeon. These restrictions removed a large proportion of potentiallyeligible surgeons from our analysis (ranging from 6 percentfor cystectomy to 72 percent for coronary-artery bypass grafting).However, because the physicians who were excluded tended tobe associated with relatively few patients (most often onlyone each), the restrictions resulted in the exclusion of a relativelylow proportion of patients from our analysis of outcomes (rangingfrom 4 percent for cystectomy to 13 percent for coronary-arterybypass grafting).
Statistical Analysis
Our primary analyses focused on the relations between surgeonvolume and hospital volume (the main variables measuring exposure)and operative mortality, defined as death before hospital dischargeor within 30 days after the index procedure. Because, for someprocedures, a large proportion of operative deaths before dischargeoccurred more than 30 days after surgery, 30-day mortality alonewould not adequately reflect the true operative mortality.
To characterize volume, we first determined the average numberof procedures that each hospital and each surgeon performedon Medicare patients during each of the two years. To make ourestimates of volume more easily interpretable, we then estimatedthe total (all-payer) volumes, using data from the 1997 NationwideInpatient Sample. As in our previous research,5 we determinedthe proportion of patients undergoing each procedure who werecovered by Medicare — which ranged from 49 percent foresophagectomy to 75 percent for carotid endarterectomy —and divided each provider's observed Medicare volume (the totalnumber of each type of procedure performed on Medicare patients)by these procedure-specific proportions. Although volume wasevaluated as a continuous (log-transformed) variable in theassessment of statistical significance, we also created categoricalvariables for volume by ranking providers in order of increasingestimated total volume and selecting cutoff points that mostclosely sorted patients into three evenly sized groups withlow, medium, and high volume. In sensitivity analyses, we recategorizedhospital volume as a binary variable according to the criteriaestablished by the Leapfrog Group for four procedures: coronary-arterybypass grafting (450 or more procedures per year vs. fewer than450), repair of abdominal aortic aneurysm (50 or more per yearvs. fewer than 50), esophagectomy (13 or more per year vs. fewerthan 13), and pancreatic resection (11 or more per year vs.fewer than 11).
We used multiple logistic-regression analyses to examine therelation between surgeon volume and operative mortality, withadjustment for characteristics of the patients.16 We used thepatient as the unit of analysis, with volume measured at thelevel of the surgeon and at the level of the hospital. All modelswere analyzed separately for each procedure. Separate modelswere used to investigate the relation between operative mortalityand surgeon volume, with and without consideration of hospitalvolume, and the relation between operative mortality and hospitalvolume, with and without consideration of surgeon volume. Toestablish the general form of the relation, we first modeledthe relations between operative mortality and the logarithmsof surgeon volume and hospital volume considered separately.We then fitted the models to the three volume strata. We adjustedfor the effect of clustering of patients within surgeons andclustering of surgeons within hospitals by using binary mixed-effectsmodels incorporating the two levels of nesting.17 Surgeons whooperated in more than one hospital were assumed to be in differentclusters and contributed a random effect for each hospital inwhich they worked. We used the statistical software packageMLwiN (Centre for Multilevel Modeling) to perform all modeling.18
We adjusted the analyses for characteristics of both the patientsand the hospitals. The characteristics of the patients for whichwe adjusted included age group (in five-year intervals), sex,race (black or nonblack), year of procedure (1998 or 1999),whether the procedure was performed electively or not, and themean income from Social Security in the ZIP Code of the patient'sresidence. Coexisting conditions were identified by their appropriateICD-9 codes, with the exclusion of conditions that were likelyto reflect either the primary indication for surgery or postoperativecomplications.5 We explored three alternative approaches tothe incorporation of data on coexisting conditions into ourmodels for risk adjustment, including the use of Charlson scoreswith published weights,19 the use of Charlson scores with weightsderived empirically for each procedure, and adjustment for allpertinent coexisting conditions as individual variables. Becauseall three approaches yielded virtually identical results, wereport only those from the models derived according to the firstapproach. We used 1998 and 1999 files from the American HospitalAssociation to ascertain the characteristics of the hospitalsspecific to the year in which the event occurred. The characteristicsof the hospitals for which we adjusted included the type ofownership (not-for-profit, for-profit, or government), location(urban or nonurban), and teaching status (as defined by Tayloret al.20).
We computed adjusted mortality rates on the basis of the averagevalues of the characteristics of the patients and the hospitalsby back-transforming predicted mortality from the logistic-regressionmodels. To assess the relative contribution of surgeon volumeto the observed associations between hospital volume and outcome,we used models that estimated the relation between the operativemortality and hospital volume, first excluding and then includinga variable for surgeon volume. The relative attenuation of theodds ratio was computed as [ORH–ORHS] ÷ [ORH–1],where ORH is the odds ratio for operative death with a givenhospital volume without consideration of surgeon volume andORHS is the odds ratio for operative death with a given hospitalvolume after adjustment for surgeon volume; both odds ratioswere adjusted for patient characteristics and other characteristicsof the hospital. A P value of less than 5 percent was consideredto indicate statistical significance, and all tests were two-sided.
Results
A total of 474,108 Medicare patients underwent one of the eightcardiac procedures or cancer resections during 1998 or 1999.Overall, approximately 25 percent of the surgeons who were includedin the study operated at more than one hospital. Patients weremuch more likely to undergo surgery performed by a low-volumesurgeon if they went to a low-volume hospital (range, 51 percentfor carotid endarterectomy to 70 percent for pancreatic resection)than if they went to a high-volume hospital (range, 6 percentfor pancreatic resection to 21 percent for carotid endarterectomy).The numbers of Medicare patients treated by low-volume, medium-volume,and high-volume surgeons in different hospital-volume strataare given in Supplementary Appendix 1 (available with the fulltext of this article at www.nejm.org).
There were negligible differences in age and sex between thepatients who received care from low-volume surgeons and thosewho received care from high-volume surgeons; for some procedures,the prevalence of coexisting conditions varied to a small degreeaccording to surgeon volume (Table 1). Patients receiving carefrom low-volume surgeons were more likely to be black and tobe admitted to the hospital nonelectively. Overall, however,there were no clinically important differences in predictedmortality rates according to surgeon volume.
Table 1. Characteristics of the Patients, According to Surgeon Volume.
When surgeon volume was assessed as a continuous variable, itwas inversely related to operative mortality for all eight procedures(P=0.003 for lung resection, P<0.001 for all other procedures).The strength of the inverse association between surgeon volumeand outcome varied markedly according to the procedure in termsof both the absolute operative mortality rate (Figure 1) andthe adjusted odds ratio for operative death (Table 2). The adjustedodds ratios for operative death among patients of low-volumesurgeons as compared with patients of high-volume surgeons rangedfrom 1.24 for lung resection to 3.61 for pancreatic resection.Adjusting for hospital volume attenuated the strength of theassociations between surgeon volume and outcome, but the effectof surgeon volume remained statistically significant for sevenof the eight procedures.
Figure 1. Adjusted Operative Mortality among Medicare Patients in 1998 and 1999, According to Surgeon-Volume Stratum, for Four Cardiovascular Procedures (Panel A) and Four Cancer Resections (Panel B).
Operative mortality was defined as the rate of death before hospital discharge or within 30 days after the index procedure. Surgeon volume was determined on the basis of the total number of procedures performed in both Medicare and non-Medicare patients. P<0.001 for all procedures except resection for lung cancer; P=0.003 for lung resection; P values reflect associations between operative mortality and volume assessed as a continuous variable.
Table 2. Adjusted Odds Ratio for Operative Death, According to Surgeon Volume and Hospital Volume.
When hospital volume was assessed as a continuous variable,it was inversely related to operative mortality for seven ofthe eight procedures (P=0.20 for carotid endarterectomy, P<0.001for all the other procedures). After adjustment for surgeonvolume, however, higher hospital volume remained a significantpredictor of decreased mortality for only four procedures (repairof an abdominal aortic aneurysm, cystectomy, lung resection,and pancreatic resection). In fact, after adjustment for surgeonvolume, high hospital volume was associated with increased mortalityamong patients undergoing carotid endarterectomy. For many procedures,surgeon volume accounted for a large proportion of the apparentdifferences in operative mortality between high-volume hospitalsand low-volume hospitals. Among patients undergoing electiverepair of an abdominal aortic aneurysm, for example, the adjustedodds ratio for death with surgery performed in a low-volumehospital as compared with that performed in a high-volume hospitaldecreased from 1.40 to 1.17 after adjustment for surgeon volume.Thus, surgeon volume accounted for 57 percent of the apparentdifference in mortality between low-volume and high-volume hospitals([1.40–1.17] ÷ [1.40–1.00]). The proportionof the apparent effect of hospital volume that was actuallyattributable to surgeon volume varied according to the procedure:it was 100 percent for aortic-valve replacement, 54 percentfor pancreatic resection, 49 percent for coronary-artery bypassgrafting, 46 percent for esophagectomy, 39 percent for cystectomy,and 24 percent for lung resection.
Figure 2 shows the relative effects of hospital volume and surgeonvolume in terms of adjusted mortality rates. For carotid endarterectomyand aortic-valve replacement, the mortality rates decreasedwith increasing surgeon volume but did not change substantiallywith increasing hospital volume. Conversely, for lung resection,the adjusted mortality rates were strongly inversely relatedto hospital volume, but were less strongly related to surgeonvolume. For the remaining five procedures, operative mortalitydecreased to relatively similar degrees with increasing hospitalvolume and increasing surgeon volume. Even within the high-volume–hospitalstratum, the patients who received their care from low-volumesurgeons had considerably higher mortality rates with severalprocedures than the patients who received care from high-volumesurgeons.
Figure 2. Adjusted Operative Mortality among Medicare Patients in 1998 and 1999, According to Hospital-Volume Stratum and Surgeon-Volume Stratum for Four Cardiovascular Procedures (Panel A) and Four Cancer Resections (Panel B).
Because of small samples (<20), mortality rates among patients treated by high-volume surgeons in low-volume hospitals are not shown for esophagectomy and pancreatic resection. Mortality rates were adjusted for characteristics of the patients.
We performed similar sensitivity analyses using the hospital-volumecriteria that were established by the Leapfrog Group for fourof the procedures (Table 3). High-volume hospitals (those withvolumes at or above the Leapfrog cutoffs) had lower overallmortality rates than low-volume hospitals, largely because patientsat high-volume hospitals were much more likely to be treatedby high-volume surgeons than by low-volume surgeons. For coronary-arterybypass grafting, elective repair of an abdominal aortic aneurysm,and esophagectomy, the operative mortality among the patientstreated by low-volume surgeons at high-volume hospitals washigher than the overall operative mortality at low-volume hospitals.For pancreatic resection, patients at high-volume hospitalshad lower mortality rates than those at low-volume hospitals,regardless of the surgeon volume.
Table 3. Adjusted Operative Mortality Rates among Medicare Patients in 1998 and 1999, According to Total Hospital Volume, Relative to the Leapfrog Group Volume Criteria and Surgeon Volume.
Discussion
By virtue of the large size and generalizability of the nationalMedicare data base, we were able to examine with precision theassociations between surgeon volume and operative mortalityfor a wide range of cardiovascular procedures and cancer resections.For all eight procedures we studied, the patients treated byhigh-volume surgeons had lower operative mortality rates thanthose treated by low-volume surgeons. Surgeon volume accountedfor a relatively large proportion of the apparent effect ofhospital volume, to a degree that varied according to the procedure.For some procedures, the association between hospital volumeand outcome disappeared almost entirely after surgeon volumehad been taken into account.
It is not surprising that the relative importance of surgeonvolume and hospital volume varies according to the procedure.In the case of carotid endarterectomy, for example, technicalskill and the use of specific intraoperative processes (e.g.,intraarterial shunt insertion and patch angioplasty)21 —processes used at the discretion of the operating surgeon —are important determinants of the risk of operative stroke ordeath. In contrast, other hospital-based services are relativelyless important. Most patients undergoing carotid endarterectomydo not require intensive postoperative management, and the lengthof stay is typically just overnight. For these reasons, thepreeminent role of surgeon volume in the outcome of this procedurehas strong intuitive validity. In the case of lung resection,in contrast, patients rarely die because of direct technicalcomplications of the procedure itself (e.g., bleeding or leakagefrom a bronchial stump); they die from cardiac events, pneumonia,and respiratory failure. Hospital-based services (e.g., intensivecare, pain management, respiratory care, and nursing care) arevery important, and the average length of stay is relativelylong. Thus, it is not surprising that hospital volume was moreimportant than surgeon volume in determining the outcome ofthis procedure. Of course, these two procedures represent theextremes. As suggested by our analysis, factors related to bothsurgeon volume and hospital volume seem to be important formost high-risk procedures.
Our study has several important limitations. First, becausewe used Medicare data, our study was restricted to patients65 years of age or older. However, the elderly constitute themajority of patients undergoing the cardiovascular proceduresand cancer resections that we examined in this study. Second,although our study was large, some of our subgroup analyseswere based on relatively small numbers of patients. In particular,the number of patients who underwent procedures performed bylow-volume surgeons at high-volume hospitals or by high-volumesurgeons at low-volume hospitals was relatively low. Thus, estimatesof mortality in these subgroups are relatively imprecise. Third,because of errors in the coding and assignment of unique provideridentification numbers, we may have incorrectly identified theoperating surgeon for some procedures. Such errors, if largelyrandom, would tend to bias our results toward the null hypothesis(no effect of surgeon volume on outcome). However, to reduceany potential bias against low-volume surgeons, we excludedphysicians who were not self-designated as surgeons.
Finally, many would question our ability to perform adequaterisk adjustment with the use of administrative data.22,23 Whetherrisk adjustment is important in studies of surgical volume andoutcome is uncertain. Some have noted that analyses based onclinical studies are less likely to report statistically significantassociations between volume and outcome than those (the majority)that are based on administrative data.4 However, clinical studiesalso tend to be substantially smaller and often lack sufficientstatistical power to detect clinically meaningful differencesin operative mortality rates. Moreover, there is little evidencefrom clinical studies that there are important, volume-relateddifferences in case mix (i.e., that low-volume providers carefor "sicker" patients). Although we cannot rule out confoundingby unmeasured characteristics of the patients in our study,there is no reason to believe that such confounding would affectour analyses of hospital volume and surgeon volume disproportionately.Thus, we do not believe that limitations related to risk adjustmentthreaten our main conclusions about the relative importanceof hospital volume and surgeon volume.
Our findings have direct implications for ongoing initiativesfor volume-based referral. Leading the most visible of theseinitiatives, the Leapfrog Group, a coalition of more than 140large public and private purchasers, has established "evidence-basedhospital referral" standards for several surgical procedures.24Although the Leapfrog Group has recently incorporated data onoutcomes and selected process measures into its 2003 standardsfor some procedures, criteria based on minimal hospital volumeremain in place for coronary-artery bypass grafting, percutaneouscoronary interventions, elective repair of an abdominal aorticaneurysm, esophagectomy, and pancreatic resection. Our analysisconfirms that hospitals that exceed the volume criteria setby Leapfrog have lower mortality rates, on average, than thosethat do not. However, our findings also suggest that high-volumehospitals have better outcomes in large part because patientsat these hospitals are more likely to be treated by high-volumesurgeons and that standards based on surgeon volume as wellas hospital volume would be more useful in directing patientsto the providers who are likely to achieve the best outcomes.Increasing surgeons' volumes would require that administratorsand leaders in the field of surgery actively manage the wayin which selected operations are distributed within their hospitals— that is, by restricting them to a smaller number ofsurgeons. Although such efforts would no doubt encounter resistance,they may be more practical and less controversial than policiesfocusing exclusively on redistributing patients among hospitals.
We should also look for opportunities to improve the qualityof surgical care delivered by low-volume surgeons. Determiningwhether this goal is realistic will require a better understandingof the mechanisms underlying the observed associations betweenvolume and outcome. The key mechanism could simply be "practice"— clinical judgment and technical skill that are achievedonly by surgeons who perform a specific procedure with sufficientfrequency. Before jumping to this conclusion, however, we mustbetter understand which specific processes of care are mostimportant to the success of various operations and the extentto which they can be exported to other surgeons or hospitals.
Supported by a grant (R01 HS10141-01) from the Agency for HealthcareResearch and Quality.
Dr. Birkmeyer reports serving as a paid consultant for the LeapfrogGroup and as the chair of its advisory panel on evidence-basedhospital referral.
The views expressed in this article are those of the authorsand do not necessarily represent those of the Center for Medicareand Medicaid Services or the U.S. government.
Source Information
From the Department of Surgery, Dartmouth–Hitchcock Medical Center, Lebanon, N.H. (J.D.B., P.P.G.); the Veterans Affairs Outcomes Group, Veterans Affairs Medical Center, White River Junction, Vt. (J.D.B., P.P.G.); the Institute for Clinical Evaluative Sciences, Toronto (T.A.S.); and the Center for Outcomes Research and Evaluation, Maine Medical Center, Portland (A.E.S., D.E.W., F.L.L.).
Address reprint requests to Dr. Birkmeyer at the Section of General Surgery, Dartmouth–Hitchcock Medical Center, Lebanon, NH 03756, or at john.birkmeyer{at}hitchcock.org.
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[Abstract][Full Text]
Wong, S. L., McCahill, L. E., Edge, S. B., Askew, R. L., Beitsch, P. D., Kollmorgen, D. R., Anthony, T., Petrelli, N. J., Leong, S. P. L., Cormier, J. N.
(2008). Getting to Better Cancer Care: Results of a Society of Surgical Oncology Survey. Ann. Surg. Oncol.
15: 2363-2371
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Rutegard, M., Lagergren, P.
(2008). No Influence of Surgical Volume on Patients' Health-Related Quality of Life After Esophageal Cancer Resection. Ann. Surg. Oncol.
15: 2380-2387
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Pech, O, Behrens, A, May, A, Nachbar, L, Gossner, L, Rabenstein, T, Manner, H, Guenter, E, Huijsmans, J, Vieth, M, Stolte, M, Ell, C
(2008). Long-term results and risk factor analysis for recurrence after curative endoscopic therapy in 349 patients with high-grade intraepithelial neoplasia and mucosal adenocarcinoma in Barrett's oesophagus. Gut
57: 1200-1206
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Schelbert, E B, Vaughan-Sarrazin, M S, Welke, K F, Rosenthal, G E
(2008). Valve type and long-term outcomes after aortic valve replacement in older patients. Heart
94: 1181-1188
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Farjah, F., Wood, D. E., Varghese, T. K. Jr, Symons, R. G., Flum, D. R.
(2008). Trends in the Operative Management and Outcomes of T4 Lung Cancer. Ann. Thorac. Surg.
86: 368-374
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Zatzick, D. F., Jurkovich, G. J., Fan, M.-Y., Grossman, D., Russo, J., Katon, W., Rivara, F. P.
(2008). Association Between Posttraumatic Stress and Depressive Symptoms and Functional Outcomes in Adolescents Followed Up Longitudinally After Injury Hospitalization. Arch Pediatr Adolesc Med
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Sheinfeld, J., Motzer, R. J.
(2008). Stage I Testicular Cancer Management and Necessity for Surgical Expertise. JCO
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Rhodes, R. S.
(2008). Grabo DJ, DiMuzio PJ, Kairys JC, McIlhenny SE, Crawford AG, Yeo CJ. Have endovascular procedures negatively impacted general surgery training? Ann Surg. 2007;246:472-480. PERSPECT VASC SURG ENDOVASC THER
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Farjah, F., Wood, D. E., Yanez, D. III, Symons, R. G., Krishnadasan, B., Flum, D. R.
(2008). Temporal Trends in the Management of Potentially Resectable Lung Cancer. Ann. Thorac. Surg.
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Carey, J. S., Parker, J. P., Brandeau, C., Li, Z.
(2008). The "occasional open heart surgeon" revisited.. J. Thorac. Cardiovasc. Surg.
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Dimick, J. B., Upchurch, G. R. Jr
(2008). Measuring and Improving the Quality of Care for Abdominal Aortic Aneurysm Surgery. Circulation
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Meek, R.M.D, Allan, D.B., McPhillips, G., Kerr, L., Howie, C.R., From the Scottish Arthroplasty Project,
(2008). Late Dislocation after Total Hip Arthroplasty. Clin Med Res
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Zahn, R, Gottwik, M, Hochadel, M, Senges, J, Zeymer, U, Vogt, A, Meinertz, T, Dietz, R, Hauptmann, K E, Grube, E, Kerber, S, Sechtem, U
(2008). Volume-outcome relation for contemporary percutaneous coronary interventions (PCI) in daily clinical practice: is it limited to high-risk patients? Results from the Registry of Percutaneous Coronary Interventions of the Arbeitsgemeinschaft Leitende Kardiologische Krankenhausarzte (ALKK). Heart
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Boutron, I., Moher, D., Altman, D. G., Schulz, K. F., Ravaud, P., for the CONSORT Group,
(2008). Extending the CONSORT Statement to Randomized Trials of Nonpharmacologic Treatment: Explanation and Elaboration. ANN INTERN MED
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Rivard, P. E., Luther, S. L., Christiansen, C. L., Shibei Zhao, , Loveland, S., Elixhauser, A., Romano, P. S., Rosen, A. K.
(2008). Using Patient Safety Indicators to Estimate the Impact of Potential Adverse Events on Outcomes. Med Care Res Rev
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Chang, A. C., Ji, H., Birkmeyer, N. J., Orringer, M. B., Birkmeyer, J. D.
(2008). Outcomes After Transhiatal and Transthoracic Esophagectomy for Cancer. Ann. Thorac. Surg.
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Boffa, D. J., Allen, M. S., Grab, J. D., Gaissert, H. A., Harpole, D. H., Wright, C. D.
(2008). Data from The Society of Thoracic Surgeons General Thoracic Surgery database: the surgical management of primary lung tumors.. J. Thorac. Cardiovasc. Surg.
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Brown, M. L., Pellikka, P. A., Schaff, H. V., Scott, C. G., Mullany, C. J., Sundt, T. M., Dearani, J. A., Daly, R. C., Orszulak, T. A.
(2008). The benefits of early valve replacement in asymptomatic patients with severe aortic stenosis.. J. Thorac. Cardiovasc. Surg.
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Michalski, C. W., Kleeff, J., Bachmann, J., AlKhatib, J., Erkan, M., Esposito, I., Hinz, U., Friess, H., Buchler, M. W.
(2008). Second-Look Operation for Unresectable Pancreatic Ductal Adenocarcinoma at a High-Volume Center. Ann. Surg. Oncol.
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Pech, O., May, A., Rabenstein, T., Ell, C.
(2007). Endoscopic resection of early oesophageal cancer. Gut
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Fleisher, L. A., Beckman, J. A., Brown, K. A., Calkins, H., Chaikof, E. L., Fleischmann, K. E., Freeman, W. K., Froehlich, J. B., Kasper, E. K., Kersten, J. R., Riegel, B., Robb, J. F., Smith, S. C. Jr, Jacobs, A. K., Adams, C. D., Anderson, J. L., Antman, E. M., Buller, C. E., Creager, M. A., Ettinger, S. M., Faxon, D. P., Fuster, V., Halperin, J. L., Hiratzka, L. F., Hunt, S. A., Lytle, B. W., Nishimura, R., Ornato, J. P., Page, R. L., Riegel, B., Tarkington, L. G., Yancy, C. W.
(2007). ACC/AHA 2007 Guidelines on Perioperative Cardiovascular Evaluation and Care for Noncardiac Surgery: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 2002 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery) Developed in Collaboration With the American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Rhythm Society, Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, Society for Vascular Medicine and Biology, and Society for Vascular Surgery. J Am Coll Cardiol
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Fleisher, L. A., Beckman, J. A., Brown, K. A., Calkins, H., Chaikof, E. L., Fleischmann, K. E., Freeman, W. K., Froehlich, J. B., Kasper, E. K., Kersten, J. R., Riegel, B., Robb, J. F.
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Nattinger, A. B., Laud, P. W., Sparapani, R. A., Zhang, X., Neuner, J. M., Gilligan, M. A.
(2007). Exploring the Surgeon Volume Outcome Relationship Among Women With Breast Cancer. Arch Intern Med
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Markman, M.
(2007). Concept of Optimal Surgical Cytoreduction in Advanced Ovarian Cancer: A Brief Critique and a Call for Action. JCO
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Hollenbeck, B. K., Hong Ji, , Zaojun Ye, , Birkmeyer, J. D.
(2007). Misclassification of Hospital Volume With Surveillance, Epidemiology, and End Results Medicare Data. SURG INNOV
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Rodgers, M., Jobe, B. A., O'Rourke, R. W., Sheppard, B., Diggs, B., Hunter, J. G.
(2007). Case Volume as a Predictor of Inpatient Mortality After Esophagectomy. Arch Surg
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Colice, G. L., Shafazand, S., Griffin, J. P., Keenan, R., Bolliger, C. T.
(2007). Physiologic Evaluation of the Patient With Lung Cancer Being Considered for Resectional Surgery: ACCP Evidenced-Based Clinical Practice Guidelines (2nd Edition). Chest
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Sundaresan, S., Langer, B., Oliver, T., Schwartz, F., Brouwers, M., Stern, H., Expert Panel on Thoracic Surgical Oncology,
(2007). Standards for Thoracic Surgical Oncology in a Single-Payer Healthcare System. Ann. Thorac. Surg.
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Cram, P., Vaughan-Sarrazin, M. S., Wolf, B., Katz, J. N., Rosenthal, G. E.
(2007). A Comparison of Total Hip and Knee Replacement in Specialty and General Hospitals. JBJS
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Glance, L. G., Osler, T. M., Mukamel, D. B., Dick, A. W.
(2007). Estimating the potential impact of regionalizing health care delivery based on volume standards versus risk-adjusted mortality rate. Int J Qual Health Care
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Vickers, A. J., Bianco, F. J., Serio, A. M., Eastham, J. A., Schrag, D., Klein, E. A., Reuther, A. M., Kattan, M. W., Pontes, J. E., Scardino, P. T.
(2007). The Surgical Learning Curve for Prostate Cancer Control After Radical Prostatectomy. JNCI J Natl Cancer Inst
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Tanner, S.
(2007). Trends in children's surgery in England. Arch. Dis. Child.
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(2007). Radical cystectomy: defining the threshold for a surgeon to achieve optimum outcomes. Postgrad. Med. J.
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Fujitani, K., Ajani, J. A., Crane, C. H., Feig, B. W., Pisters, P. W., Janjan, N., Walsh, G. L., Swisher, S. G., Vaporciyan, A. A., Rice, D., Welch, A., Baker, J., Faust, J., Mansfield, P. F.
(2007). Impact of Induction Chemotherapy and Preoperative Chemoradiotherapy on Operative Morbidity and Mortality in Patients with Locoregional Adenocarcinoma of the Stomach or Gastroesophageal Junction. Ann. Surg. Oncol.
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(2007). Relationship of Physician Volume With Process Measures and Outcomes in Diabetes. Diabetes Care
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(2007). Better Survival in Patients with Esophageal Cancer After Surgical Treatment in University Hospitals: A Plea for Performance by Surgical Oncologists. Ann. Surg. Oncol.
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Fujitani, K., Ajani, J. A., Crane, C. H., Feig, B. W., Pisters, P. W., Janjan, N., Walsh, G. L., Swisher, S. G., Vaporciyan, A. A., Rice, D., Welch, A., Baker, J., Faust, J., Mansfield, P. F.
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(2007). Missed Diagnosis of Subarachnoid Hemorrhage in the Emergency Department. Stroke
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(2007). Randomized Controlled Trial of Resection Versus Radiotherapy After Induction Chemotherapy in Stage IIIA-N2 Non-Small-Cell Lung Cancer. JNCI J Natl Cancer Inst
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Porter, M. E., Teisberg, E. O.
(2007). How Physicians Can Change the Future of Health Care. JAMA
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Weber, W. P., Guller, U., Jain, N. B., Pietrobon, R., Oertli, D.
(2007). Impact of Surgeon and Hospital Caseload on the Likelihood of Performing Laparoscopic vs Open Sigmoid Resection for Diverticular Disease: A Study Based on 55 949 Patients. Arch Surg
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Gammie, J. S., O'Brien, S. M., Griffith, B. P., Ferguson, T. B., Peterson, E. D.
(2007). Influence of Hospital Procedural Volume on Care Process and Mortality for Patients Undergoing Elective Surgery for Mitral Regurgitation. Circulation
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Rouvelas, I., Lindblad, M., Zeng, W., Viklund, P., Ye, W., Lagergren, J.
(2007). Impact of Hospital Volume on Long-term Survival After Esophageal Cancer Surgery. Arch Surg
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Kahn, K. L.
(2007). On Referral Patterns for Patients With Breast Cancer. JCO
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Katz, S. J., Hofer, T. P., Hawley, S., Lantz, P. M., Janz, N. K., Schwartz, K., Liu, L., Deapen, D., Morrow, M.
(2007). Patterns and Correlates of Patient Referral to Surgeons for Treatment of Breast Cancer. JCO
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Berry, J. G., Lieu, T. A., Forbes, P. W., Goldmann, D. A.
(2007). Hospital Volumes for Common Pediatric Specialty Operations. Arch Pediatr Adolesc Med
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Billingsley, K. G., Morris, A. M., Dominitz, J. A., Matthews, B., Dobie, S., Barlow, W., Wright, G. E., Baldwin, L.-M.
(2007). Surgeon and Hospital Characteristics as Predictors of Major Adverse Outcomes Following Colon Cancer Surgery: Understanding the Volume-Outcome Relationship. Arch Surg
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Parekh, D. J., Bochner, B. H., Dalbagni, G.
(2006). Superficial and Muscle-Invasive Bladder Cancer: Principles of Management for Outcomes Assessments. JCO
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Tien, H. C., Farrell, R., Macdonald, J.
(2006). Preparing Canadian military surgeons for Afghanistan.. CMAJ
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DiSesa, V. J., O'Brien, S. M., Welke, K. F., Beland, S. M., Haan, C. K., Vaughan-Sarrazin, M. S., Peterson, E. D.
(2006). Contemporary Impact of State Certificate-of-Need Regulations for Cardiac Surgery: An Analysis Using the Society of Thoracic Surgeons' National Cardiac Surgery Database. Circulation
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Liu, J. H., Zingmond, D. S., McGory, M. L., SooHoo, N. F., Ettner, S. L., Brook, R. H., Ko, C. Y.
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Khan, K., Campbell, A., Wallington, T., Gardam, M.
(2006). The impact of physician training and experience on the survival of patients with active tuberculosis.. CMAJ
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Steyerberg, E. W., Neville, B. A., Koppert, L. B., Lemmens, V. E.P.P., Tilanus, H. W., Coebergh, J.-W. W., Weeks, J. C., Earle, C. C.
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Teufelsbauer, H., Polterauer, P., Lammer, J., Huk, I., Nanobachvili, J., Kretschmer, G.
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Parekh, D.
(2006). Laparoscopic-Assisted Pancreatic Necrosectomy: A New Surgical Option for Treatment of Severe Necrotizing Pancreatitis. Arch Surg
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Shishehbor, M. H., Litaker, D., Lauer, M. S.
(2006). Mediators of the Association Between Mortality Risk and Socioeconomic Status--Reply. JAMA
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Brotman, D. J.
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(2006). Carotid Stenting. Circulation
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Ho, V., Heslin, M. J., Yun, H., Howard, L.
(2006). Trends in Hospital and Surgeon Volume and Operative Mortality for Cancer Surgery. Ann. Surg. Oncol.
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Judge, A., Chard, J., Learmonth, I., Dieppe, P.
(2006). The effects of surgical volumes and training centre status on outcomes following total joint replacement: analysis of the Hospital Episode Statistics for England. J Public Health (Oxf)
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Konety, B. R., Allareddy, V., Modak, S., Smith, B.
(2006). Mortality After Major Surgery for Urologic Cancers in Specialized Urology Hospitals: Are They Any Better?. JCO
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Feudtner, C., Silveira, M. J., Shabbout, M., Hoskins, R. E.
(2006). Distance From Home When Death Occurs: A Population-Based Study of Washington State, 1989-2002. Pediatrics
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Ferri, L. E., Law, S., Wong, K.-H., Kwok, K.-F., Wong, J.
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David, T. E.
(2006). Should cardiac surgery be performed in low-volume hospitals?. J. Thorac. Cardiovasc. Surg.
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Francis, D. O., Beckman, H., Chamberlain, J., Partridge, G., Greene, R. A.
(2006). Introducing a Multifaceted Intervention to Improve the Management of Otitis Media: How Do Pediatricians, Internists, and Family Physicians Respond?. American Journal of Medical Quality
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Birkmeyer, N. J.O., Birkmeyer, J. D.
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Shishehbor, M. H., Litaker, D., Pothier, C. E., Lauer, M. S.
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Lipscomb, J.
(2006). Transcending the Volume-Outcome Relationship in Cancer Care. JNCI J Natl Cancer Inst
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Schrag, D., Earle, C., Xu, F., Panageas, K. S., Yabroff, K. R., Bristow, R. E., Trimble, E. L., Warren, J. L.
(2006). Associations Between Hospital and Surgeon Procedure Volumes and Patient Outcomes After Ovarian Cancer Resection. JNCI J Natl Cancer Inst
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Trivedi, A. N., Sequist, T. D., Ayanian, J. Z.
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Nallamothu, B. K., Wang, Y., Magid, D. J., McNamara, R. L., Herrin, J., Bradley, E. H., Bates, E. R., Pollack, C. V. Jr, Krumholz, H. M., for the National Registry of Myocardial Infarction,
(2006). Relation Between Hospital Specialization With Primary Percutaneous Coronary Intervention and Clinical Outcomes in ST-Segment Elevation Myocardial Infarction: National Registry of Myocardial Infarction-4 Analysis. Circulation
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Freixinet, J. L., Julia-Serda, G., Rodriguez, P. M., Santana, N. B., de Castro, F. R., Fiuza, M. D., Lopez-Encuentra, A., Bronchogenic Carcinoma Cooperative Group of the Sp,
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Babikian, V. L., Wolf, P. A.
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Welke, K. F., Barnett, M. J., Vaughan Sarrazin, M. S., Rosenthal, G. E.
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Vitale, M. A., Heyworth, B. E., Skaggs, D. L., Roye, D. P. Jr., Lipton, C. B., Vitale, M. G.
(2005). Comparison of the Volume of Scoliosis Surgery Between Spine and Pediatric Orthopaedic Fellowship-Trained Surgeons in New York and California. JBJS
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(2005). Glycemic Control in the Intensive Care Unit: Why We Should Wait for NICE-SUGAR. Mayo Clin Proc.
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Nallamothu, B. K., Eagle, K. A., Ferraris, V. A., Sade, R. M.
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Michelet, P., D'Journo, X.-B., Roch, A., Papazian, L., Ragni, J., Thomas, P., Auffray, J.-P.
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Flum, D. R., Salem, L., Broeckel Elrod, J. A., Dellinger, E. P., Cheadle, A., Chan, L.
(2005). Early Mortality Among Medicare Beneficiaries Undergoing Bariatric Surgical Procedures. JAMA
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Al-Khatib, S. M., Lucas, F. L., Jollis, J. G., Malenka, D. J., Wennberg, D. E.
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Schelbert, E. B., Rosenthal, G. E., Welke, K. F., Vaughan-Sarrazin, M. S.
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