Below is a sample of some of the best research on the generally high skills of high-volume doctors. You can find older studies in their end notes, and each entry gives the newer studies which cite them.
There is also a research study on the two causes of high volume: more referrals to the best doctors, and practice makes perfect. Companion articles address training of doctors and how to find high-volume doctors.
CANCER, HEART AND ANEURYSM SURGERY
"Surgeon volume and operative mortality in the United States." Birkmeyer JD, Stukel TA, Siewers AE, Goodney PP, Wennberg DE, Lucas FL, N Engl J Med. 2003 Nov 27;349(22):2117-27. with comments Cited by 101 articles.
"Patients can often improve their chances of survival substantially, even at high-volume hospitals, by selecting surgeons who perform the operations frequently...
"Increasing surgeons’ volumes would require that administrators and leaders in the field of surgery actively manage the way in which selected operations are distributed within their hospitals — that is, by restricting them to a smaller number of surgeons. Although such efforts would no doubt encounter resistance, they may be more practical and less controversial than policies focusing exclusively on redistributing patients among hospitals."
Low-volume surgeons had 1 to 10 more deaths per 100 patients than high-volume surgeons. See table above.
All types of surgeons had similarly risky patients: "there were no clinically important differences in predicted mortality rates [patient risk] according to surgeon volume."
The study counted deaths within 30 days of the operation (or during the same hospital stay, even if longer than 30 days), based on 470,000 Medicare patients in 1998-99. Surgeon volume includes estimates of non-Medicare patients. These estimates can be fractions.
"Is volume related to outcome in health care? A systematic review and methodologic critique of the literature." Halm EA, Lee C, Chassin MR, Ann Intern Med. 2002 Sep 17;137(6):511-20. Cited by 160 articles.
"69% of studies of physician volume reported a statistically significant association between higher volume and better health outcomes. No study documented a statistically significant association between higher volume and worse outcomes."
"[T]he most striking differences in mortality rates between high- and low-volume surgeons were seen for pancreatic cancer, ruptured abdominal aortic aneurysm, and pediatric cardiac surgery (median differences of 3 to 14 deaths per 100 cases for the three procedures). Surgeon volume seemed to be a more important determinant of outcomes than hospital volume in the case of CABG, carotid endarterectomy, surgery for ruptured abdominal aortic aneurysm, and surgery for colorectal cancer."
"Increasing evidence shows that high-volume providers may more consistently use proven effective therapies, such as aspirin or beta-blockers in [heart attacks] or adjuvant [followup chemo, radiation, or hormones] therapy in breast cancer...
"We found a positive association between physician volume and outcome in 62% of studies with no risk adjustment, 68% of those with risk adjustment using administrative data, and 73% of investigations using clinical risk-adjustment models."
A summary article in 2007 quotes a British specialist that death rates are lowest at hospitals which treat 43 or more abdominal aortic aneurysms per year.
Newer articles include:
Verma V, Allen PK, Simone CB 2nd, Gay HA, Lin SH. Association of Treatment at High-Volume Facilities With Survival in Patients Receiving Chemoradiotherapy for Nasopharyngeal Cancer.JAMA Otolaryngol Head Neck Surg. 2017 Nov 2. doi: 10.1001/jamaoto.2017.1874. [Epub ahead of print] PMID: 29098291 DOI:10.1001/jamaoto.2017.1874
Chen YW, Mahal BA, Muralidhar V, et al. Association between treatment at a high-volume facility and improved survival for radiation-treated men with high-risk prostate cancer. Int J Radiat Oncol Biol Phys. 2016;94(4):683-690.
Haque W, Verma V, Butler EB, Teh BS. Definitive chemoradiation at high volume facilities is associated with improved survival in glioblastoma. J Neurooncol. 2017. doi:10.1007/s11060-017-2563-0
"Relationship between annual volume of patients treated by admitting physician and mortality after acute myocardial infarction." Tu JV, Austin PC, Chan BT, JAMA. 2001 Jun 27;285(24):3116-22. Cited by 20 articles.
"Patients with AMI [heart attack] who are treated by high-volume admitting physicians are more likely to survive at 30 days and 1 year."
"The 30-day risk-adjusted mortality rate was 15.3% for physicians who treated 5 or fewer AMI cases per year (lowest quartile) compared with 11.8% for physicians who treated more than 24 AMI cases annually (highest quartile; P<.001). The 1-year risk-adjusted mortality rate was 24.2% for physicians who treated 5 or fewer AMI cases per year (lowest quartile) compared with 19.6% for physicians who treated more than 24 AMI cases annually (highest quartile; P<.001)...
"Physician volume is a well-established determinant of outcomes after invasive cardiac procedures. Previous studies have demonstrated an inverse relationship between annual surgeon volume of coronary artery bypass graft (CABG) procedures and in-hospital mortality and between annual cardiologist volume of percutaneous coronary interventions (PCIs) procedures and complication rates after the procedure. [notes 1- 3] These associations have led to development of American Heart Association/American College of Cardiology guidelines that recommend a minimum annual volume of procedures that should be performed by cardiac surgeons and invasive cardiologists...
"Physicians who treated the most patients on an annual basis had the lowest 30-day and 1-year patient mortality rates, even after adjusting for potential confounders. The impact of physician volume on outcomes of AMI [heart attack] patients was comparable with the impact of physician volume on outcomes of invasive cardiac procedures... The association between physician volume and mortality was robust and existed across physician specialties.
"The results of our study are consistent with a previous study conducted using Pennsylvania hospital discharge data from 1993 that demonstrated an inverse association between physician volume and in-hospital mortality after an AMI. That study demonstrated that patients of low-volume physicians who treated 1 to 6 AMI patients per year had a 43% higher in-hospital mortality rate than high-volume physicians, defined as those who treated 24 or more AMI patients per year... Physician volume was a stronger predictor of 30-day AMI mortality than was physician specialty in both our study and the Pennsylvania analysis...
"our results do suggest that significant reductions in AMI mortality could be achieved by shifting the primary responsibility for treating more AMI patients to a smaller number of high-volume physicians. Hospitals that have low-volume physicians could consider designating a few physicians to handle all of their AMI cases or they could mandate that low-volume physicians work with high-volume physicians when treating AMI patients."
The study counted deaths among 98,000 heart attack patients at Ontario hospitals from 1992-1998.
The graph below shows death rates decline steadily as the number of heart attack patients treated by a doctor rise from 1-2 to 34 or more per year:
"2011 ACCF/AHA Guideline for Coronary Artery Bypass Graft Surgery" American College of Cardiology Foundation/American Heart Association, pp. 35-36
" 5.1.1... Class I - 1. All cardiac surgery programs should participate in a state, regional, or national clinical data registry and should receive periodic reports of their risk-adjusted outcomes..." Patients can ask for these "periodic reports" cited in the American Heart Association guideline 5.1.1
"Class IIb - 1. Affiliation with a high-volume tertiary center might be considered by cardiac surgery programs that perform fewer than 125 CABG procedures annually...
"In general, the best results are achieved most consistently by high-volume surgeons in high-volume hospitals and the worst results by low-volume surgeons in low-volume hospitals. (notes 793,794) However, many low-volume programs achieve excellent results, perhaps related to appropriate case selection; effective teamwork among surgeons, nurses, anesthesiologists, perfusionists, and physician assistants; and adoption of best practices derived from larger programs. (notes 833,834)
"As a quality assessment strategy, participation in a state, regional, or national clinical data registry that provides regular performance feedback reports is highly recommended for all cardiac programs. Random sampling variation is greater at low volumes... Ultimately, state or national regulatory authorities must decide whether the lower average performance of very small programs and the added difficulty in accurately measuring their performance are outweighed by other considerations, such as the need to maintain cardiac surgery capabilities in rural areas with limited access to referral centers."
They cite many studies on supplemental pages 33-39. Most address hospital volume, not surgeon volume.
"The role of surgeon volume on patient outcome in total knee arthroplasty: a systematic review of the literature" Rick L Lau, Anthony V Perruccio, Rajiv Gandhi, and Nizar N Mahomed. BMC Musculoskelet Disord. 2012; 13: 250. Cited by 3 articles.
"Mortality rate, survivorship and thromboembolic events [clots] were not found to be associated with surgeon volume [of knee replacements]. We found a significant association between low surgeon volume and higher rate of infection (0.26% - 2.8% higher), procedure time (165 min versus 135 min), longer length of stay (0.4 - 2.13 days longer [in hospital]), transfusion rate (13% versus 4%), and worse patient reported outcomes...
"After reviewing the available studies, we would identify a high surgeon volume as > 50 TKA [Total Knee Replacements] per year. Three studies identified a statistically significant relationship between low surgeon volume and higher infection rates (0.26% - 2.8% higher)...
"Early to midterm (up to 8 years) implant survivorship did not appear to be influenced by surgeon volume [notes 18,25,32]. Whether similar findings hold over the longer-term (i.e. >8 years) is unknown...
"In the one study which examined patient-reported outcomes, Katz et al (2007) reported a positive association between LV [Low Volume] surgeons and poorer TKA outcomes [in US Medicare, study summary below]...
"Evidence suggests that some patients would refuse to have surgery in an unfamiliar setting, preferring to attend a local health provider with lower procedure volume [notes 35,52]. In the US, the poor, less educated, elderly, as well as racial/ethnic minorities are more likely to undergo TKA at low volume centers [notes 11,36,38]. Regionalization of TKA to high volume centres and surgeons may further exacerbate existing disparities in the utilization of TKA and restrict access to some patients who would otherwise use a low volume provider for TKA, increasing the number of patients who decline or defer their elective TKA surgery with resultant poorer health outcomes [notes 2,11,53]. A regionalization program involving referral to high volume surgeons and hospitals might decrease the already low rate of perioperative complications at the cost of increasing arthritis related disability [note 11]. Evidence suggests that having TKA in low volume hospitals costs more and produces worse outcomes than having TKA in high volume centers, but having TKA in low volume centers is still more cost effective than not having TKA at all [note 35]. While these studies were specific to examining the role of hospital volume on cost effectiveness of TKA, it is possible that the same may hold true for surgeon volume and TKA."
"Association of hospital and surgeon procedure volume with patient-centered outcomes of total knee replacement in a population-based cohort of patients age 65 years and older." Katz JN, Mahomed NN, Baron JA, Barrett JA, Fossel AH, Creel AH, Wright J, Wright EA, Losina E. Arthritis Rheum. 2007 Feb;56(2):568-74. Cited by 30 articles.
"The questionnaires assessed lower extremity functional status using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) [notes 17,18]. The WOMAC contains... a 17-item scale that assesses lower extremity functional status...
"Scores <60 indicated poor outcome. Sixty is a typical preoperative score... WOMAC functional status scores <60 increased from 10% among patients of surgeons who performed >50 cases per year in the Medicare population to 20% among surgeons who performed ≤12 per year...
"Patients operated upon in higher volume hospitals by higher volume surgeons had the lowest rates of worse functional outcomes (WOMAC functional status score <60, unable to flex the knee 90 degrees, unable to extend knee fully), while patients operated upon by lower volume surgeons in lower volume centers had the highest rates of these poor functional outcomes...
The risk of a poor WOMAC score ranged from 8.4% for patients in the high-volume centers operated upon by a high-volume surgeon to 22.6% for patients in low-volume centers operated upon by low-volume surgeons... The finding of a volume effect on function and range of knee motion, but not on pain or satisfaction, suggests possible mechanisms. In high- and low-volume settings, the pain generator, the arthritic knee, is removed during surgery in all patients. Thus, pain relief is generally excellent. However, low-volume surgeons in low-volume centers may be less skilled at soft tissue balancing required to achieve the normal motion necessary for full function."
The study used questionnaires from a random sample of 906 Medicare patients 2 years after their total knee replacements, which were in 2000. These provided a 58% response rate among those sampled and invited.
"Early failures of total hip replacement: effect of surgeon volume." Losina E, Barrett J, Mahomed NN, Baron JA, Katz JN. Arthritis Rheum. 2004 Apr;50(4):1338-43. Cited by 30 articles.
"Clinicians should consider surgeon volume among the factors influencing their referrals for elective THR." [Total Hip Replacement]
"Patients of low-volume surgeons have higher rates of revision THR than patients of high-volume surgeons, particularly within the first 18 months postoperatively."
15,000 elective Medicare hip replacements were done in 1995 by surgeons who did less than 12 Medicare hip replacements that year. 4.5% of these needed to be redone (revised) within 4 years, usually within 18 months. Among the 42,000 hip replacements done by surgeons who did 12 or more, 3.5% needed to be redone. This is a noticeable difference if you are in the 1% who avoided a second hip replacement. See graph below.
"Our definition of THR failure was simply the occurrence of a revision THR. Clearly, patients can have a poor outcome of THR yet not receive revision surgery, either because they prefer not to have surgery or because they are poor surgical candidates...
"Medicare population represent at least 67% of the total number of THRs performed in the US."
"Proficiency of surgeons in inguinal hernia repair: effect of experience and age." Neumayer LA, Gawande AA, Wang J, Giobbie-Hurder A, Itani KM, Fitzgibbons RJ Jr, Reda D, Jonasson O; CSP #456 Investigators. Ann Surg. 2005 Sep;242(3):344-8; discussion 348-52. Cited by 5 articles
"Surgeon's inexperience and older age were significant predictors of recurrence in laparoscopic herniorraphy [repair]... This analysis demonstrates that surgeon's age of 45 years and older, when combined with inexperience in laparoscopic inguinal herniorraphies, increases risk of recurrence... We found a significantly higher recurrence rate in the laparoscopic group (10%) than in the open group (5%). Surgeons reporting experience with more than 250 laparoscopic herniorraphies before the beginning of the study, however, had recurrence rates with laparoscopic repair equivalent to that with open repair (5%)." Both types of repairs in this study placed mesh in the patient.
This study reports the experience of the "attending" or teaching surgeon. 96% of the operations also had an intern or resident, as discussed in the Training section.
Attending "Surgeons 45 years and older at the beginning of our study would have learned these [laparoscopic] techniques after completion of a surgical residency through a variety of means, including short courses and formal or informal preceptorships... The inadequacy of effective learning programs was sharply evident when experience was lacking... The methods of teaching older surgeons new techniques may need to be modified."
This study reported higher recurrence for experienced young attending surgeons than for inexperienced; there were only 2 experienced young attending surgeons.
Much higher volumes of hernia repair are done at the specialist Shouldice Hospital in Ontario, where each surgeon repairs 600-800 hernias per year. Furthermore the assistant surgeons are not interns or residents. They have 1% recurrence (based on 65,000 cases in 1993-2007), compared to 5% in other Ontario hospitals (170,000 cases), and 5-10% in the US.
"If the operations had all been recorded, the situations where error occurred could be identified... This would lead to more specific courses of instruction, which should improve outcomes. It almost certainly would shorten the average learning curve from 250 cases to a more practical number... A commitment to making video records a routine aspect of future trials on surgical technique has much to recommend it...
"Hernias are traditionally one of the first operations that surgeons assist junior residents during surgery training... We believe in the majority of open repairs, that the resident was on the side of the hernia, and presumably was the person making the cut and putting the stitches in.
TWO CAUSES OF HIGH VOLUME
"The volume-outcome relationship: practice-makes-perfect or selective-referral patterns?" Luft HS, Hunt SS, Maerki SC. Health Serv Res. 1987 Jun;22(2):157-82. ncbi.nlm.nih.gov/pmc/articles/PMC1065430/ Cited by 50 articles.
A common explanation of good work with high volume is the, " 'practice-makes-perfect' hypothesis. An alternative explanation is that physicians and hospitals with better outcomes attract more patients - the "selective-referral pattern" hypothesis. Using data for 17 categories of patients from a sample of over 900 hospitals... both explanations are valid, and that the relative importance of the practice or referral explanation varies by diagnosis or procedure, in ways consistent with clinical aspects of the various patient categories."
Four "Procedures and diagnoses... exhibit high volumes resulting in lower death rates, but there is no measurable influence of outcomes on volume; that is, the practice-makes-perfect effect predominates. All four of these, acute myocardial infarction [heart attack], stomach operations, intestinal operations, and cholecystectomy [remove gallbladder], are usually managed by the family physician or a general surgeon, perhaps in consultation with local cardiologists or gastroenterologists. There is little reason to seek outside specialty consultations, so referrals to centers with particularly good outcomes are unlikely."
For four others "the selective-referral effect predominates. Volume has no effect on death rates, but hospitals with low death rates attract patients with abdominal aortic aneurysm, fracture of the femur... transurethral resection of the prostate, and coronary artery bypass graft...
"Insurers are developing preferred provider organizations with financial incentives for enrollees to use selected hospitals... if only the practice-makes-perfect hypothesis is applicable, then the selection criterion is irrelevant. Regionalization efforts will improve outcomes in the selected hospitals-and perhaps worsen them in those that lose patients.
"However, if selective-referral patterns are" important, outcomes "may worsen markedly if the higher-quality settings are excluded and if increased volume in the selected hospitals does not improve outcomes sufficiently to offset the loss of the better providers... the possibility that unmeasured, but nonetheless important, physician and hospital factors influence outcomes and that existing referral patterns may already reflect such factors. Policymakers and insurance companies must also be cautious, because the results suggest that the roles of practice, referral, and other factors vary across diagnoses and procedures."
"If primary physicians initially choose specialists at random, then switch referrals after one "bad outcome," patients eventually are directed away from providers with outcomes truly worse than average. Furthermore, even if the majority of patients go to the nearest hospital or otherwise make decisions independent of perceived outcomes, a minority seeking or referred to the "best provider in town" (or referred away from "poor-quality providers") will result in a selective referral pattern for specific diagnoses and procedures... The question, therefore, is whether some patients are influenced in their choice of physicians and hospitals by relative performance, not whether all patients are so influenced...
[H]igher-than-expected volumes for a specific procedure or diagnosis may, in fact, be the best single indicator of exceptionally good outcomes... As an analogy, consider the situation of a new visitor to a city... indication of relative quality might be the number of patrons in each [restaurant]. Our visitor would probably be wise to avoid places that are nearly empty and, if there is no hurry, a long line would be not only a measure of popularity but perhaps the best single indicator of good food within a given price range."
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