Original Article
The Effect of the Volume of Procedures at Transplantation Centers on Mortality after Liver Transplantation
N Engl J Med 1999; 341:2049-2053December 30, 1999DOI: 10.1056/NEJM199912303412703
- Abstract
Background
For many complex surgical procedures there is an association between a low volume of procedures and an increased risk of death for the patients who undergo the procedures.
Methods
We examined the effect of the volume of procedures at transplantation centers on the risk of death after liver transplantation. We analyzed all liver transplantations performed in the United States between October 1, 1987, and April 30, 1994. Because the results for 1987 to 1991 were largely similar to those from 1992 to 1994, we focused on the more recent period.
Results
Between January 1, 1992, and April 30, 1994, 47 centers performed 20 or fewer liver transplantations each per year (total, 837 transplantations) and were designated low-volume centers, and 52 centers performed more than 20 transplantations each per year (total, 6526) and were designated high-volume centers. The one-year mortality rate for the low-volume centers was 25.9 percent, as compared with 20.0 percent for the high-volume centers. Thirteen centers, all of which had low volumes, had one-year mortality rates of more than 40 percent. Low-volume centers that were affiliated with high-volume centers, such as pediatric transplantation programs, had results similar to those of the high-volume centers. The one-year mortality rate at unaffiliated low-volume centers was 28.3 percent, as compared with a rate of 20.1 percent for the group of all high-volume centers plus affiliated low-volume centers (P<0.001).
Conclusions
As a group, liver-transplantation centers in the United States that perform 20 or fewer transplantations per year have mortality rates that are significantly higher than those at centers that perform more than 20 transplantations per year. Information regarding the outcome of liver transplantation at transplantation centers should be made widely available to the public.
Media in This Article
Figure 1
Relation between the Number of Procedures Performed per Year and the Mortality Rate One Year after Liver Transplantation at 99 Centers from January 1, 1992, to April 30, 1994.Figure 2
Kaplan–Meier Estimates of Survival at One Year, According to the Number of Transplantations Performed per Year.Article Activity
- Article
Currently, organ transplantation is limited by the availability of donor organs. In the United States, there have been small increases in the number of donor organs available. Nonetheless, since 1994, a rapid rise in the number of patients awaiting transplantation has led to longer waiting times and a greater number of deaths each year among patients on waiting lists for transplants. The death of a patient soon after transplantation also represents the loss of an organ that might have saved another patient's life.
In 1994, Hosenpud et al.1 analyzed the effect of the volume of procedures at transplantation centers on survival after cardiac transplantation. They found that the risk of death was 33.1 percent higher 12 months after transplantation in centers that performed fewer than nine transplantations per year than in those that performed nine or more procedures. A multivariate analysis demonstrated that the risk of death was independent of differences in the characteristics of the patients from center to center. We used the same methods to examine the effect of the volume of procedures on the risk of death after liver transplantation.
Methods
We analyzed all liver transplantations performed in the United States between October 1, 1987, and April 30, 1994. We excluded recipients of partial liver transplants from living donors and patients who underwent multiorgan transplantations, in which the liver and other organs from a single donor are transplanted into one recipient. The data were verified by the individual transplantation centers and organ-procurement organizations in conjunction with the 1997 Report of Center-Specific Graft and Patient Survival Rates, 2 a study of the outcome of all solid-organ transplantations conducted under the auspices of the Health Resources and Services Administration of the Department of Health and Human Services.
To estimate the effect of the volume of procedures at a center on the risk of death after transplantation while controlling for differences among centers in the donors' and recipients' characteristics, we used a generalized additive model, an extension of standard logistic regression.3 This model is a useful exploratory tool for obtaining simultaneous estimates of the effects of covariates that may be nonlinear. Many of the donor and recipient covariates included in the model were used in the analysis of liver-transplantation outcomes in the 1997 Report of Center-Specific Graft and Patient Survival Rates. 2 The list of covariates included characteristics of the recipients (the number of previous transplantations, age, race, diagnosis, medical condition at the time of transplantation, the serum creatinine concentration at transplantation, and the year of transplantation) and factors related to the donor (age, race, and the duration of cold ischemia).
The outcome measure was the mortality rate one year after transplantation. To determine the relation between the volume of procedures and the risk of death, we determined the average number of transplantations performed per year at each center. The log-transformed value was included as an additional covariate in the generalized additive model; log transformation corrected for the fact that there were only a few centers with very large volumes. An estimate of the effect of the number of procedures performed per year was calculated on the basis of data obtained during two periods: October 1, 1987, to December 31, 1991, and January 1, 1992, to April 30, 1994. Rather than choose arbitrary volume categories, we grouped the centers into two categories on the basis of these analyses.
Many low-volume centers were identified as being closely affiliated with adjacent centers that had high volume; many of these affiliated centers were pediatric programs in separate but affiliated pediatric hospitals. In a preliminary analysis, we found that the outcome was markedly poorer at low-volume centers that were not affiliated with high-volume centers than at all other centers as a group. Therefore, for some analyses, the centers were subcategorized as affiliated or unaffiliated.
To determine the final estimate of the effect of the number of procedures performed per year on the one-year mortality rate, we entered the data for 1992 to 1994 into a multivariate logistic-regression model in which the response variable was the death of the patient within one year after transplantation. In this model, rather than excluding patients with insufficient follow-up, we weighted the data on patients who were not followed up for one year.3 An indicator variable was created for the category of the center as determined from the generalized additive model, and this variable was included in the logistic-regression model along with the donor and recipient covariates. The modal category or mean values were used for covariates with missing data; for example, data on the duration of cold ischemia were missing for 6.7 percent of transplantations, whereas data on other covariates were missing for less than 1 percent.
Because follow-up was not complete, particularly in the case of transplantations performed in 1992 or later, unadjusted mortality rates were calculated according to the Kaplan–Meier method.4 All statistical calculations were performed with S-Plus for Windows (version 3.3, StatSci, Seattle) or SAS (version 6.09, SAS Institute, Cary, N.C.) statistical software. In the analysis of the patients' characteristics, the chi-square test was used for categorical variables5 and the t-test was used for continuous variables.6 Differences in survival curves were compared with the use of the log-rank test.7 All reported P values are two-sided.
Results
Table 1Table 1
Characteristics of the Liver-Transplantation Centers, According to the Average Number of Procedures Performed per Year, 1987–1994. shows the number of transplantation centers and the number of transplantations performed from October 1, 1987, to December 31, 1991, and from January 1, 1992, to April 30, 1994. Between January 1, 1992, and April 30, 1994, 47 centers performed 20 or fewer liver transplantations each per year and 52 performed more than 20 per year. The centers in the low-volume group (20 or fewer transplantations per year) performed 11 percent of all transplantations during this period, whereas high-volume centers (more than 20 procedures per year) performed 89 percent.The relation between the number of procedures performed per year and the mortality rate one year after liver transplantation from 1992 to 1994, as determined by the generalized additive model, is shown in Figure 1Figure 1
Relation between the Number of Procedures Performed per Year and the Mortality Rate One Year after Liver Transplantation at 99 Centers from January 1, 1992, to April 30, 1994. and closely resembles the findings for the period from 1987 to 1991 (data not shown). During both periods, mortality rates stabilized at centers that performed more than 20 transplantations per year and increased inversely with transplantation volumes of less than 20 per year. Thirteen centers, all of which had low volumes, had mortality rates of 40 percent or more. Accordingly, using the data for 1992 to 1994, we grouped centers into those that performed 20 or fewer transplantations per year and those that performed more than 20 per year.We used logistic-regression analysis to estimate the odds of death at one year for transplantations performed during the period from 1992 to 1994 at centers categorized according to the number of procedures per year and affiliation status, after adjustment for the following covariates: donor's age and race and recipient's age, race, diagnosis, number of previous liver transplantations, serum creatinine concentration at the time of transplantation, medical condition at the time of transplantation, and year of transplantation. The performance of affiliated low-volume centers and affiliated high-volume centers was similar, as was the performance of affiliated and unaffiliated high-volume centers (Table 2Table 2
Relation between the Number of Procedures Performed per Year and Affiliation Status and the Risk of Death One Year after Liver Transplantation, 1992–1994.). In a separate comparison of low-volume centers, the odds of death within one year after liver transplantation at all unaffiliated centers was nearly twice that at all affiliated centers (adjusted odds ratio, 1.97; 95 percent confidence interval, 1.32 to 2.94). Therefore, in the remainder of the analyses, the centers were divided into two groups: unaffiliated low-volume centers and high-volume centers plus affiliated low-volume centers. As compared with the odds of death for the entire group of high-volume centers and affiliated low-volume centers, the odds ratio for death at low-volume unaffiliated centers was 2.04 (95 percent confidence interval, 1.63 to 2.55).The characteristics of the donors and the liver-transplant recipients are shown in Table 3Table 3
Characteristics of Liver-Transplant Donors and Recipients, 1992–1994.. Donors and recipients at unaffiliated low-volume centers were younger than those at high-volume centers and affiliated low-volume centers. The percentage of recipients who were less than 18 years of age was similar in the two groups. Recipients at unaffiliated low-volume centers were more likely to be black and less likely to have received a previous liver transplantation. Figure 2Figure 2Kaplan–Meier Estimates of Survival at One Year, According to the Number of Transplantations Performed per Year. shows Kaplan–Meier estimates of survival at one year. The survival rates were significantly higher (P<0.001) in the group of high-volume centers and affiliated low-volume centers than in the unaffiliated low-volume centers. The difference in mortality rates between the two groups was 6.8 percentage points at 90 days and 8.2 percentage points at 1 year (Table 3).It has been suggested that the sickest liver recipients may have a higher risk of death if they undergo transplantation at low-volume centers. Using the logistic-regression model, we tested this hypothesis for recipients of a second transplant and for those who were receiving life support at the time of transplantation. Patients who were receiving life support at the time of transplantation had a higher risk of death if they underwent the procedure at an unaffiliated low-volume center rather than at a high-volume center or an affiliated low-volume center (mortality rate, 51.4 percent vs. 39.3 percent; adjusted odds ratio, 2.2; 95 percent confidence interval, 1.25 to 3.74). For recipients of a second or subsequent transplant, the mortality rate was 64.4 percent at unaffiliated low-volume centers, as compared with 41.3 percent at the other centers (adjusted odds ratio, 3.1; 95 percent confidence interval, 0.99 to 9.88). The wide confidence intervals reflect the small number of recipients of a second or subsequent transplant at low-volume centers (31 recipients).
Discussion
We found that, as a group, liver-transplantation centers in the United States that perform 20 or fewer transplantations per year had mortality rates that were significantly higher than those at centers that perform more than 20 transplantations per year. The effect on mortality of the number of procedures performed per year was even greater when low-volume centers that were affiliated with a high-volume center were compared with low-volume centers that were not so affiliated. In the initial analysis, we found that a significant number of children underwent transplantation at affiliated low-volume centers and that the results were similar to those at high-volume centers.
The increased risk of death in the unaffiliated low-volume centers did not appear to be an effect of the patients selected. Patients who are in the intensive care unit and those who are receiving life support at the time of liver transplantation have a higher risk of death than do healthier liver-transplant recipients.2 The percentages of transplantations that were performed in patients who were receiving life support or were in the intensive care unit at the time of the procedure were similar in unaffiliated low-volume centers and the entire group of affiliated low-volume centers plus all high-volume centers. The outcome of transplantation for these sicker patients was poorer at the unaffiliated low-volume centers. A higher percentage of black patients underwent transplantation at low-volume unaffiliated centers. Black patients have a higher mortality rate after liver transplantation than white patients.8 Our analysis adjusted for the potential effect of the recipient's race on the risk of death.
We found that some centers that perform 20 or fewer liver transplantations per year had a low mortality rate. In part, this may reflect statistical variation. It may also reflect other factors that we were unable to measure.
The association between a low volume of procedures and an increased risk of death among patients undergoing complex surgical procedures is well established.9,10 It is therefore not surprising that we found an association between the number of procedures performed per year and the outcome of liver transplantation. The responsible factors might include the experience of the center and the experience and skill of the surgeons. In the case of heart transplantation,1 Hosenpud et al. found no difference in the risk of death among the first 10 patients who underwent transplantation at a center as compared with the next 10 patients, suggesting that the accumulated experience of the center was not an important factor in determining survival. We have also found that cumulative experience at a liver-transplantation center was not a factor in determining mortality (data not shown).
Is there adequate information to enable physicians to steer their patients away from transplantation centers with high mortality rates? Thirteen centers had mortality rates that exceeded 40 percent, and the rate at one of these centers was 100 percent (Figure 1). It would be reasonable to assume that, given this information, patients would decide to undergo transplantation at a center with low mortality rates.
Our findings suggest that the information available to patients and referring physicians is inadequate or that regional health care systems may be forcing patients to go to centers with poor results. Information regarding the outcomes of liver transplantation at transplantation centers should be made widely available to the public in a timely manner.
Source Information
From the United Network for Organ Sharing, Richmond, Va. (E.B.E., M.A.M.); the University of California at San Francisco, San Francisco (J.P.R.); University Hospitals of Cleveland, Cleveland (J.A.S.); and the University of Iowa College of Medicine, Iowa City (L.G.H.).
- References
References
1
Hosenpud JD ,Breen TJ ,Edwards EB ,Daily OP ,Hunsicker LG . The effect of transplant center volume on cardiac transplant outcome: a report of the United Network for Organ Sharing Registry. JAMA 1994;271:1844-1849
CrossRef | Web of Science | Medline2
1997 Report of center-specific graft and patient survival rates: executive summary. Richmond, Va.: United Network for Organ Sharing, 1997.
3
Hastie T ,Tibshirani R . Generalized additive models. Stat Sci 1986;1:297-318
CrossRef4
Kaplan EL ,Meier P . Nonparametric estimation from incomplete observations. J Am Stat Assoc 1958;53:457-481
CrossRef | Web of Science5
Agresti A. Categorical data analysis. New York: John Wiley, 1990.
6
Bhattacharyya GK, Johnson RA. Statistical concepts and methods. New York: John Wiley, 1977.
7
Kalbfleisch JD, Prentice RL. The statistical analysis of failure time data. New York: John Wiley, 1980.
8
1996 Annual report of the U.S. Scientific Registry of Transplant Recipients and the Organ Procurement and Transplantation Network: transplant data 1988–1995. Richmond, Va.: United Network for Organ Sharing, 1996.
9
Gordon TA ,Burleyson GP ,Tielsch JM ,Cameron JL . The effects of regionalization on cost and outcome for one general high-risk surgical procedure. Ann Surg 1995;221:43-49
CrossRef | Web of Science | Medline10
Kazmers A ,Jacobs L ,Perkins A ,Lindenauer SM ,Bates E . Abdominal aortic aneurysm repair in Veterans Affairs medical centers. J Vasc Surg 1996;23:191-200
CrossRef | Web of Science | Medline
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Citing Articles
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2
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5
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6
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7
J. M. Miro, M. Montejo, L. Castells, A. Rafecas, S. Moreno, F. Agüero, M. Abradelo, P. Miralles, J. Torre-Cisneros, J. D. Pedreira, E. Cordero, G. de la Rosa, B. Moyano, A. Moreno, I. Perez, A. Rimola, . (2012) Outcome of HCV/HIV-Coinfected Liver Transplant Recipients: A Prospective and Multicenter Cohort Study. American Journal of Transplantationno-no
8
Deepak K. Ozhathil, You Fu Li, Jillian K. Smith, Jennifer F. Tseng, Reza F. Saidi, Adel Bozorgzadeh, Shimul A. Shah. (2011) Impact of center volume on outcomes of increased-risk liver transplants. Liver Transplantation 17:10, 1191-1199
9
A. W. Avolio, U. Cillo, M. Salizzoni, L. De Carlis, M. Colledan, G. E. Gerunda, V. Mazzaferro, G. Tisone, R. Romagnoli, L. Caccamo, M. Rossi, A. Vitale, A. Cucchetti, L. Lupo, S. Gruttadauria, N. Nicolotti, P. Burra, A. Gasbarrini, S. Agnes, . (2011) Balancing Donor and Recipient Risk Factors in Liver Transplantation: The Value of D-MELD with Particular Reference to HCV Recipients. American Journal of Transplantationno-no
10
Sue V. McDiarmid, Ravinder Anand, Karen Martz, Michael J. Millis, George Mazariegos. (2011) A Multivariate Analysis of Pre-, Peri-, and Post-Transplant Factors Affecting Outcome After Pediatric Liver Transplantation. Annals of Surgery 254:1, 145-154
11
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12
G. Yağci, S. Çetiner, N. Ersöz, İ. Hakki Özerhan, M.F. Can, F. Bilgin, A. Coşar, S. Bağci, B. Üstünsöz, Y. Karslioğlu. (2011) The Effect of Gained Experience on Postoperative Complications and Mortality in Cadaveric Liver Transplantation: A Single-Center Experience. Transplantation Proceedings 43:3, 912-916
13
Karen B. Domino. (2010) Where Should Patients With Severe Traumatic Brain Injury Be Managed? Is a Generalist Care Center Adequate for Patient Safety?. Journal of Neurosurgical Anesthesiology 22:4, 360
14
Juan C. Gutierrez, Michael C. Cheung, Ying Zhuge, Leonidas G. Koniaris, Juan E. Sola. (2010) Does Children's Oncology Group hospital membership improve survival for patients with neuroblastoma or Wilms tumor?. Pediatric Blood & Cancer 55:4, 621-628
15
Jeffrey H. Shuhaiber, Jeff Moore, David B. Dyke. (2010) The effect of transplant center volume on survival after heart transplantation: A multicenter study. The Journal of Thoracic and Cardiovascular Surgery 139:4, 1064-1069
16
John E. Scarborough, Kyla M. Bennett, Robert D. Davis, Shu S. Lin, Elizabeth T. Tracy, Paul C. Kuo, Theodore N. Pappas. (2010) Temporal Trends in Lung Transplant Center Volume and Outcomes in the United States. Transplantation 89:6, 639-643
17
Elisabeth T. Tracy, Kyla M. Bennett, Melissa E. Danko, Diana L. Diesen, Tammy J. Westmoreland, Paul C. Kuo, Theodore N. Pappas, Henry E. Rice, John E. Scarborough. (2010) Low volume is associated with worse patient outcomes for pediatric liver transplant centers. Journal of Pediatric Surgery 45:1, 108-113
18
Elisabeth T. Tracy, Kyla M. Bennett, Emeline M. Aviki, Theodore N. Pappas, Bradley H. Collins, Janet E. Tuttle-Newhall, Carlos E. Marroquin, Paul C. Kuo, John E. Scarborough. (2009) Temporal trends in liver transplant centre volume in the USA. HPB 11:5, 414-421
19
Ralf Zahn, Uwe Zeymer. (2009) Akuter Myokardinfarkt: Akut-PCI in jedem Krankenhaus versus Akut-PCI im spezialisierten Zentrum. Herz Kardiovaskuläre Erkrankungen 34:3, 211-217
20
Michelle L. Mayer, Heather A. Beil, Daniel von Allmen. (2009) Distance to care and relative supply among pediatric surgical subspecialties. Journal of Pediatric Surgery 44:3, 483-495
21
P. P. Reese, H. Yeh, A. M. Thomasson, J. Shults, J. F. Markmann. (2009) Transplant Center Volume and Outcomes After Liver Retransplantation. American Journal of Transplantation 9:2, 309-317
22
Robert P. Myers, Hude Quan, James N. Hubbard, Abdel Aziz M. Shaheen, Gilaad G. Kaplan. (2009) Predicting in-hospital mortality in patients with cirrhosis: Results differ across risk adjustment methods. Hepatology 49:2, 568-577
23
R. B. Freeman, Jr. (2008) SOFT Endpoints in Liver Transplantation. American Journal of Transplantation 8:12, 2483-2484
24
Karen I. Kroeker, Vincent G. Bain, Thomas Shaw-Stiffel, Tse-Ling Fong, Eric M. Yoshida. (2008) Adult liver transplant survey: policies towards eligibility criteria in Canada and the United States 2007. Liver International 28:9, 1250-1255
25
John E. Scarborough, Ricardo Pietrobon, Janet E. Tuttle-Newhall, Carlos E. Marroquin, Bradley H. Collins, Dev M. Desai, Paul C. Kuo, Theodore N. Pappas. (2008) Relationship Between Provider Volume and Outcomes For Orthotopic Liver Transplantation. Journal of Gastrointestinal Surgery 12:9, 1527-1533
26
Ashwin N. Ananthakrishnan, Emily L. McGinley, Kia Saeian. (2008) Effect of hospital volume and teaching status on outcomes of acute liver failure. Liver Transplantation 14:9, 1347-1356
27
SUE PONDROM. (2008) The AJT Report. American Journal of Transplantation 8:6, 1083-1084
28
Fernando J. Bianco. (2008) Radical prostatectomy: Surgical planning, execution, and outcomes. Current Urology Reports 9:3, 231-236
29
Robert D. Ecker, Eric Sauvageau, Elad I. Levy, L. Nelson Hopkins. (2008) COMPLICATIONS OF CAROTID ARTERY STENTING AT A HIGH-VOLUME TEACHING CENTER. Neurosurgery 62:4, 812-816
30
Vincent B. Nieuwenhuijs, John W. Chen, Libby John, John Ring, Hugh Harley, Paul M. Dolan, Robert T. A. Padbury. (2008) LIVER TRANSPLANTATION: A SMALL-VOLUME UNIT EXPERIENCE. ANZ Journal of Surgery 78:3, 128-133
31
See Ching Chan, Sheung Tat Fan, Chung Mau Lo, Chi Leung Liu, William I. Wei, Barbara Hsia-Ying Chik, John Wong. (2008) A Decade of Right Liver Adult-to-Adult Living Donor Liver Transplantation. Transactions of the ... Meeting of the American Surgical Association 126, 61-69
32
Richard B. Freeman. (2007) Predicting the future?. Liver Transplantation 13:11, 1503-1505
33
Tae Hoon Lee, Nilay Shah, Rachel A. Pedersen, Walter K. Kremers, Charles B. Rosen, Goran B. Klintmalm, W. Ray Kim. (2007) Survival after liver transplantation: Is racial disparity inevitable?. Hepatology 46:5, 1491-1497
34
Richard B. Freeman. (2007) Is waiting time a measure of access to liver transplantation? Is shorter necessarily better?. Hepatology 46:2, 602-603
35
Katherine S. Panageas, Deborah Schrag, A. Russell Localio, E. S. Venkatraman, Colin B. Begg. (2007) Properties of analysis methods that account for clustering in volume–outcome studies when the primary predictor is cluster size. Statistics in Medicine 26:9, 2017-2035
36
Jennifer T. Anger, Larissa V. Rodríguez, Qin Wang, Chris L. Pashos, Mark S. Litwin. (2007) The Role of Provider Volume on Outcomes After Sling Surgery for Stress Urinary Incontinence. The Journal of Urology 177:4, 1457-1462
37
Nina Shervin, Harry E Rubash, Jeffrey N Katz. (2007) Orthopaedic Procedure Volume and Patient Outcomes. Clinical Orthopaedics and Related Research 457, 35-41
38
Elijah Dixon, Sebastian Schneeweiss, Janice L. Pasieka, Oliver F. Bathe, Francis Sutherland, Christopher Doig. (2007) Mortality following liver resection in US medicare patients: Does the presence of a liver transplant program affect outcome?. Journal of Surgical Oncology 95:3, 194-200
39
Peter C. Enzinger, Jacqueline K. Benedetti, Jeffrey A. Meyerhardt, Sheryl McCoy, Scott A. Hundahl, John S. Macdonald, Charles S. Fuchs. (2007) Impact of Hospital Volume on Recurrence and Survival After Surgery for Gastric Cancer. Annals of Surgery 245:3, 426-434
40
M. M. Chowdhury, H. Dagash, A. Pierro. (2007) A systematic review of the impact of volume of surgery and specialization on patient outcome. British Journal of Surgery 94:2, 145-161
41
Folke Nilsson, Rolf Ekroth, John Wallwork. (2007) Fewer centers will increase quality and safety in cardiothoracic transplantation. Scandinavian Cardiovascular Journal 41:5, 275-276
42
Robert D. Ecker, Elad I. Levy, L Nelson Hopkins. (2006) Workforce Needs for Endovascular Neurosurgery. Neurosurgery 59:SUPPLEMENT, S3-271-S3-276
43
P. G. Northup, T. L. Pruett, G. J. Stukenborg, C. L. Berg. (2006) Survival After Adult Liver Transplantation Does Not Correlate with Transplant Center Case Volume in the MELD Era. American Journal of Transplantation 6:10, 2455-2462
44
Daniel Azoulay, Paola Andreani, Umberto Maggi, Chadi Salloum, Fabiano Perdigao, Myl??ne Sebagh, Antoinette Lemoine, Ren?? Adam, Denis Castaing. (2006) Combined Liver Resection and Reconstruction of the Supra-Renal Vena Cava. Annals of Surgery 244:1, 80-88
45
Marie-Odile Serinet, Pierre Broué, Emmanuel Jacquemin, Alain Lachaux, Jacques Sarles, Frédéric Gottrand, Frédéric Gauthier, Christophe Chardot. (2006) Management of patients with biliary atresia in France: Results of a decentralized policy 1986-2002. Hepatology 44:1, 75-84
46
Gabriel C. Oniscu, John L.R. Forsythe. (2006) The Assembly Line Approach in Kidney Transplantation???Back to the Future?. Transplantation 81:11, 1523-1524
47
Balazs Nemes, Wojtek Polak, Gabor Ther, Herman Hendriks, Laszlo Kobori, Robert J. Porte, Eniko Sarvary, Koert P. de Jong, Attila Doros, Zsuzsa Gerlei, Aad P van den Berg, Imre Fehervari, Denes Gorog, Paul M. Peeters, Jeno Jaray, Maarten J. H Slooff. (2006) Analysis of differences in outcome of two European liver transplant centers. Transplant International 19:5, 372-380
48
Richard B. Freeman. (2006) Liver allocation: the intent-to-treat approach. Transplant International 19:4, 270-274
49
Fabiola Delcò, Markus J. Muller. (2006) Does a liver center make sense from a cost perspective?. Journal of Hepatology 44:4, 642-646
50
Linda L Wong, Whitney Limm, Alan Cheung, Hiroji Noguchi. (2006) Liver transplant in Hawaii: the survival of a small centre. Clinical Transplantation 20:1, 55-61
51
Justin B. Dimick, John D. Birkmeyer, Gilbert R. Upchurch. (2005) Measuring Surgical Quality: What’s the Role of Provider Volume?. World Journal of Surgery 29:10, 1217-1221
52
Oren Shibolet, Mina Rowe, Rifaat Safadi, Izhar Levy, Gideon Zamir, Ahmed Eid, Yoel Donchin, Yaron Ilan, Daniel Shouval. (2005) Air transportation of patients with end-stage liver disease to distant liver transplantation centers. Liver Transplantation 11:6, 650-655
53
Michael R. Lucey, Manal F. Abdelmalek, Rosemarie Gagliardi, Darla Granger, Curtis Holt, Igal Kam, Goran Klintmalm, Alan Langnas, Kirti Shetty, Andreas Tzakis, E. Steve Woodle. (2005) A Comparison of Tacrolimus and Cyclosporine in Liver Transplantation: Effects on Renal Function and Cardiovascular Risk Status. American Journal of Transplantation 5:5, 1111-1119
54
Natividad Cuende, Blanca Miranda, Jose F. Ca????n, Gregorio Garrido, Rafael Matesanz. (2005) Donor Characteristics Associated with Liver Graft Survival. Transplantation 79:10, 1445-1452
55
Mark L. Barr, Robert C. Bourge, Jonathan B. Orens, Kenneth R. McCurry, W. Steves Ring, Tempie E. Hulbert-Shearon, Robert M. Merion. (2005) Thoracic organ transplantation in the United States, 1994-2003. American Journal of Transplantation 5:4p2, 934-949
56
Luc Massicotte, Marie-Pascale Sassine, Serge Lenis, Robert F. Seal, André Roy. (2005) Survival rate changes with transfusion of blood products during liver transplantation. Canadian Journal of Anesthesia/Journal canadien d'anesthésie 52:2, 148-155
57
Kim M. Olthoff, Robert M. Merion, Rafik M. Ghobrial, Michael M. Abecassis, Jeffrey H. Fair, Robert A. Fisher, Chris E. Freise, Igal Kam, Timothy L. Pruett, James E. Everhart, Tempie E. Hulbert-Shearon, Brenda W. Gillespie, Jean C. Emond. (2005) Outcomes of 385 Adult-to-Adult Living Donor Liver Transplant Recipients. Transactions of the ... Meeting of the American Surgical Association 123:&NA;, 21-31
58
F. Kanwal, G. S. Dulai, B. M. R. Spiegel, H. F. Yee, I. M. Gralnek. (2005) A comparison of liver transplantation outcomes in the pre- vs. post-MELD eras. Alimentary Pharmacology and Therapeutics 21:2, 169-177
59
Aloke K. Mandal, Nicholas Drew, Jodi A. Lapidus. (2004) The effect of center volume on pancreas transplant outcomes. Surgery 136:2, 225-231
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Atif Zaman. (2004) ALL???S FAIR IN LOVE AND WAR: MELD SCORES AND THE IMPACT OF ORGAN ALLOCATION. Evidence-Based Gastroenterology 5:3, 90-91
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Chung-Mau Lo, Sheung Tat Fan, Chi Leung Liu, Boon Hun Yong, Yik Wong, George K. Lau, Ching Lung Lai, Irene O. Ng, John Wong. (2004) Lessons Learned From One Hundred Right Lobe Living Donor Liver Transplants. Annals of Surgery 240:1, 151-158
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David A. Axelrod, Mary K. Guidinger, Keith P. McCullough, Alan B. Leichtman, Jeffrey D. Punch, Robert M. Merion. (2004) Association of Center Volume with Outcome After Liver and Kidney Transplantation. American Journal of Transplantation 4:6, 920-927
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Ziv Ben-Ari, Hemda Weiss-Schmilovitz, Jaqueline Sulkes, Marius Brown, Nathan Bar-Nathan, Ezra Shaharabani, Alexander Yussim, Zaki Shapira, Ran Tur-Kaspa, Eytan Mor. (2004) Serum cholestasis markers as predictors of early outcome after liver transplantation. Clinical Transplantation 18:2, 130-136
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Kazim Sheikh. (2003) Reliability of Provider Volume and Outcome Associations for Healthcare Policy. Medical Care 41:10, 1111-1117
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Afschin Gandjour, Angelika Bannenberg, Karl W. Lauterbach. (2003) Threshold Volumes Associated With Higher Survival in Health Care. Medical Care 41:10, 1129-1141
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John A. Goss, George Soltes, Sarah E. Goodpastor, Merle Barth, Russell Lam, Charles F. Brunicardi, Tatiana Froud, Rodolfo Alejandro, Camillo Ricordi. (2003) PANCREATIC ISLET TRANSPLANTATION. Transplantation 76:1, 199-203
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Jerome H Liu, David A Etzioni, Jessica B O'Connell, Melinda A Maggard, Clifford Y Ko. (2003) Using Volume Criteria: Do California Hospitals Measure Up?. Journal of Surgical Research 113:1, 96-101
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John P. Roberts, Robert S. Brown, Erick B. Edwards, Douglas G. Farmer, Richard B. Freeman, Russell H. Wiesner, Robert M. Merion. (2003) Liver and intestine transplantation. American Journal of Transplantation 3:s4, 78-90
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J. M. A. Smits, J. De Meester, M. C. Deng, H. H. Scheld, M. Hummel, F. Schoendube, A. Haverich, J. Vanhaecke, H. C. van Houwelingen. (2003) Mortality rates after heart transplantation: How to compare center-specific outcome data?. Transplantation 75:1, 90-96
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Daniel Azoulay, Marcello M. Linhares, Emmanuel Huguet, Valérie Delvart, Denis Castaing, René Adam, Philippe Ichai, Faouzi Saliba, Antoinette Lemoine, Didier Samuel, Henri Bismuth. (2002) Decision for Retransplantation of the Liver. Annals of Surgery 236:6, 713-721
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Deborah Schrag, Katherine S. Panageas, Elyn Riedel, Laura D. Cramer, Jose G. Guillem, Peter B. Bach, Colin B. Begg. (2002) Hospital and Surgeon Procedure Volume as Predictors of Outcome Following Rectal Cancer Resection. Annals of Surgery 236:5, 583-592
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Mark D. McKee, Michael D. Cropp, Andrew Hyland, Nancy Watroba, Brian McKinley, Stephen B. Edge. (2002) Provider case volume and outcome in the evaluation and treatment of patients with mammogram-detected breast carcinoma. Cancer 95:4, 704-712
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Alois Gratwohl, Jakob Passweg, Helen Baldomero, Bruno Horisberger, Alvaro Urbano-Ispizua, . (2002) Economics, health care systems and utilization of haematopoietic stem cell transplants in Europe. British Journal of Haematology 117:2, 451-468
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F. Trevisani, P. Caraceni, M. Simoncini, M. Micati, M. Domenicali, F. Dazzani, A. Zambruni, C. Stefanelli, G. Grazi, B. Nardo, C. Guarnieri, M. Bernardi. (2002) Evidence of oxidative imbalance in long-term liver transplant patients. Digestive and Liver Disease 34:4, 279-284
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Bach , Peter B. , Cramer , Laura D. , Schrag , Deborah , Downey , Robert J. , Gelfand , Sarah E. , Begg , Colin B. , . (2001) The Influence of Hospital Volume on Survival after Resection for Lung Cancer. New England Journal of Medicine 345:3, 181-188
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Cronin , David C. II , Millis , J. Michael , Siegler , Mark , . (2001) Transplantation of Liver Grafts from Living Donors into Adults — Too Much, Too Soon. New England Journal of Medicine 344:21, 1633-1637
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Daniel Azoulay, Denis Castaing, René Adam, Eric Savier, Valérie Delvart, Vincent Karam, Bao Yan Ming, Monzer Dannaoui, Jinane Krissat, Henri Bismuth. (2001) Split-Liver Transplantation for Two Adult Recipients: Feasibility and Long-Term Outcomes. Annals of Surgery 233:4, 565-574
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Dirk J. Gouma, Rutger C. I. van Geenen, Thomas M. van Gulik, Rob J. de Haan, Laurens T. de Wit, Olivier R. C. Busch, Huug Obertop. (2000) Rates of Complications and Death After Pancreaticoduodenectomy: Risk Factors and the Impact of Hospital Volume. Annals of Surgery 232:6, 786-795
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Richard N Pierson, Aaron P Milstone, James E Loyd, Ben H Lewis, C.Wright Pinson, E.Wesley Ely. (2000) Lung allocation in the United States, 1995–1997: an analysis of equity and utility. The Journal of Heart and Lung Transplantation 19:9, 846-851
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James H. Sorrell, Michael F. Sorrell. (2000) Liver transplantation and organ procurement. Current Gastroenterology Reports 2:4, 265-267
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(2000) Volume of Procedures at Transplantation Centers and Mortality after Liver Transplantation. New England Journal of Medicine 342:20, 1527-1528
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