Elsevier

The Lancet

Volume 382, Issue 9898, 28 September–4 October 2013, Pages 1121-1129
The Lancet

Series
Understanding of regional variation in the use of surgery

https://doi.org/10.1016/S0140-6736(13)61215-5Get rights and content

Summary

The use of common surgical procedures varies widely across regions. Differences in illness burden, diagnostic practices, and patient attitudes about medical intervention explain only a small degree of regional variation in surgery rates. Evidence suggests that surgical variation results mainly from differences in physician beliefs about the indications for surgery, and the extent to which patient preferences are incorporated into treatment decisions. These two components of clinical decision making help to explain the so-called surgical signatures of specific procedures, and why some consistently vary more than others. Variation in clinical decision making is, in turn, affected by broad environmental factors, including technology diffusion, supply of specialists, local training frameworks, financial incentives, and regulatory factors, which vary across countries. Better scientific evidence about the comparative effectiveness of surgical and non-surgical interventions could help to mitigate regional variation, but broader dissemination of shared decision aids will be essential to reduce variation in preference-sensitive disorders.

Introduction

A patient's odds of undergoing surgery often depend more on where he or she lives than on clinical circumstances. Almost 75 years ago, J Alison Glover1 noted that tonsillectomy rates in Britain varied substantially according to school district. In 1936, for example, a child in Enfield was 20 times more likely to undergo the operation than was a child in Hornsey, even though only 7 miles separated the two districts. 35 years later, Wennberg and Gittelsohn2 noted that rates of tonsillectomy varied almost 12-fold across counties in rural Vermont, USA, and other common procedures varied almost as much. This study and subsequent analyses based on data from New England served to usher in the specialty of small-area analysis.3, 4, 5

Despite substantial advances in medical science, there is little evidence that regional variation in the use of surgery is shrinking over time. Although investigators of some studies have documented small improvements in variations in medical practice,6, 7, 8 the relative degree of variation in population-based rates of ten common surgical procedures has been remarkably stable over the past 20 years.9 In 2008–10, rates of hip replacement, coronary bypass surgery, prostatectomy, and many other major procedures continued to vary at least four-fold to five-fold across hospital referral regions (figure 1). Data from the UK showed similar degrees of variation in the use of surgery in 152 primary care trusts in 2009–10.10, 12

In this Review, we examine the major determinants of regional variation in procedure rates. After considering the role of patient demand, we review the evidence that surgical variation shows differences in physicians' beliefs about the value of surgery in specific circumstances, and in the extent to which they incorporate patient preferences into surgical decisions. We consider how surgery rates—and regional variation—are affected by external factors, such as new technology, surgeon supply, and financial incentives. Finally, although we focus on regional variation within countries, we also consider the scientific literature on small-area analysis in the context of international differences in the use of surgery. Although others have suggested alternative models of variation in medical practice,13 in this Review we focus on the framework of clinical decision making, which we believe best fits present evidence about the root causes of regional variation in the use of surgery.

Key messages

  • Studies from many different countries show that the use of surgical procedures varies across regions

  • Chance, patient demand, and differences in diagnostic practices have a small role in explanation of regional variation in surgical rates

  • Different attitudes and beliefs about the indications for surgery are the most important reasons for surgical variation

  • Discretionary, preference-sensitive procedures, such as radical prostatectomy, tend to vary considerably more than do procedures for which clinical decisions are constrained to a narrow range of options—eg, colectomy for colon cancer

  • Tools to better incorporate the preferences of individual patients, such as decision aids, might help to reduce variation for preference-sensitive procedures

  • Broad factors that affect regional variation include technology diffusion, training, the regional supply of surgeons, and financial incentives and the regulatory environment

Section snippets

Variation in patient demand for surgery

Some regions might have higher rates of specific procedures because of greater demand for surgery there. We use the term demand in a broad sense, to describe patient-related factors affecting the real or perceived need for surgery upstream of decisions made by surgeons. Such factors include the true incidence of surgically treatable disease, the frequency in which subclinical disease is detected with medical testing, and the willingness of patients to undergo surgical intervention. Each of

Variation in physician beliefs about the clinical indications for surgery

The most obvious, and most important, reason for regional variation in surgery rates is that physicians have different attitudes and beliefs about the indications for surgery. In some instances, variation in procedure rates results from differences in decisions by physicians about whether to refer patients to surgeons in the first place. In seminal studies in the 1930s, Glover concluded that variation in tonsillectomy rates across English school districts resulted mainly from differences in the

Variation in incorporation of patient preferences into surgical decisions

For some surgically treatable disorders, the decision about whether to intervene should depend as much on patient preferences as on scientific evidence about clinical effectiveness. The value of any given surgical intervention depends on tradeoffs between its benefits and risks. When there are large imbalances between the two, surgical decisions are clear cut and procedure rates tend to vary little. Regional variation becomes more pronounced when such tradeoffs are a close call, or when they

Interpretation of geographical patterns of surgical variation

The importance of clinical uncertainty and patient preferences is shown in the variation profiles of different procedures. The relative degree to which surgical interventions vary is commonly measured with the systematic component of variation (SCV). An SCV is more robust than other measures of variation because it distinguishes variation between areas (systematic variation) from variation within areas (random variation), and as a result shows the true, non-random part of observed variation in

Broad effects on regional variation in surgery rates

Although in this Series paper we have focused on understanding of regional variation of surgery rates in a framework of clinical decision making, treatment decisions are affected by many broad environmental factors (figure 2). Diffusion of surgical innovations and new technologies can enhance regional variation in practice patterns. New procedures or new approaches to established procedures can contribute to variation simply by increasing the number of therapeutic alternatives available to

International comparisons

Rates of common surgical procedures also vary substantially across international boundaries. On the basis of data from the 1990s, rates of spine surgery were 164% higher in the USA than in Canada.57 In more recent comparisons, rates of carotid interventions (either endarterectomy or stenting) were substantially higher in the USA (300 per 100 000 Medicare beneficiaries in 2006) than across ten European countries (9·6 per 100 000 in 2008).58, 59 Such disparities no doubt result from international

Conclusions

Practice variation is, of course, not unique to surgical care. Similar regional disparities have been described for patterns of medication prescription,64, 65, 66 the use of radiological imaging,67 and admission rates to hospital.10, 68, 69 The consequences for a patient of an operation can be much more serious than those of a prescription or a radiograph; regional variation in surgery—and its implication that many patients are getting procedures they do not want or need—has therefore garnered

Search strategy and selection criteria

We searched Ovid Medline and Embase for articles between 1946 and May 1, 2013, and constructed our searches with the use of a combination of MeSH or EMTREE controlled terms (such as, “small-area analysis”, “physician's practice patterns”, and “clinical practice”) and title and abstract keywords. We used the following keywords, plus various derivatives: “regional”, “geographic”, “population”, “treatment”, “small area”, or “care”, adjacent to “variation” or “pattern”, in combination with

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