Can The Edmonton Obesity Staging System Better Guide Indications for Bariatric Surgery?

Current recommendations for bariatric surgery are largely based on BMI levels, although the presence of comorbidities has been used to justify surgical interventions at lower BMIs.

While there is little doubt that current data suggest that bariatric surgery can alleviate and, in some cases, reverse the impact of excess weight on a wide range of comorbidities and improve quality of life, these benefits are less clear for individuals, who do not have these problems to begin with.

Indeed, we have previously noted that a significant number of patients currently undergoing bariatric surgery may have rather limited overall risk and that data on putative health benefits in terms of disease prevention remain rather sparse.

In out recent analysis of the Edmonton Obesity Staging System (EOSS) in the NHANES population, we therefore specifically examined the ability of EOSS to predict mortality risk in individuals, who meet current BMI, age, and comormiditiy criteria in surgical guidelines and expert consensus statements.

In this subgroup of participants, despite adjustment for metabolic syndrome or hypertriglyceridemic waistline, EOSS substantially outperformed BMI criteria.

In fact, while individuals with Class III obesity (after adjustment for metabolic syndrome or waist line) had virtually no increased mortality risk compared to Class II obese individuals (HR 0.9), individuals with EOSS 2 or 3 had a four to twelve-fold greater hazard ratio, respectively, compared to individuals with EOSS 0/1.

In light of these data, we discuss the potential role of EOSS in determining indications for bariatric surgery as follows:

“Currently, most patients are selected for surgery on the basis of BMI thresholds alone and have few obesity related comorbidities. The practice of selecting patients using BMI alone has been criticized as inaccurate and arbitrary and may result in the selection of patients who are least likely to benefit from weight reduction.9 Prioritizing patients with higher Edmonton obesity staging system scores — and thus greater comorbidity and risk of death — may help maximize the benefits of surgery.”

Obviously, this view may not be shared by some bariatric surgeons, who often highlight the ‘preventive’ nature of their intervention, their argument being that it may be better to operate early to preempt and hopefully prevent the development of relevant comorbidities.

Unfortunately, this argument does not wash.

Firstly, as shown in our studies, there are a substantial number of patients even with Class III obesity, who may have minimal mortality risk over the rather lengthy observation periods of the NHANES III and ACLS cohorts (almost 20 years); notably this observation period is substantially longer than all current bariatric surgical studies (perhaps with the exception of the Swedish Obesity Study).

Secondly, little is known about the ‘natural history’ of obesity in that we currently do not have good predictors of who will indeed progress to higher EOSS stages and who will remain weight stable and ‘healthy’. Thus the notion of ‘prevention’ will need to be looked at in prospective studies before assuming that such ‘preventive’ surgery is in fact both cost-effective and offers a reasonable risk/benefit ratio.

Thirdly, the need to preempt many of the obesity related comorbidities may be less ‘urgent’ than some surgeons suggest. This is because virtually all of the obesity related comorbidities are largely ‘reversible’, especially in patients defined as EOSS 2 (no clinically relevant target organ damage). Thus, there is ample time to still operate and expect reasonable outcomes when patients actually progress to EOSS 2.

The notion of ‘preventive’ surgery is therefore, perhaps not as convincing, as some surgeons may wish us to believe.

It is also very likely that a formal health economic analysis based on EOSS criteria will likely strongly support the cost-effectiveness of bariatric surgery for EOSS 2/3 patients, with minimal (if any) cost-effectiveness (even in the long-term) in EOSS 0/1 individuals.

Thus, we strongly feel, that EOSS may well serve as a tool in guiding indications for bariatric surgery and will likely attract considerable attention from payers. At least in a publicly funded health care system, it may be prudent to argue that patients with EOSS 2/3 should likely be prioritized to make best use of limited access and resources.

I certainly look forward to what I am sure will be a most lively debate, especially as I head out to present our findings at the forthcoming International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO) meeting in Hamburg early next month.

AMS
Toronto, Ontario

Padwal RS, Pajewski NM, Allison DB, & Sharma AM (2011). Using the Edmonton obesity staging system to predict mortality in a population-representative cohort of people with overweight and obesity. CMAJ : Canadian Medical Association journal = journal de l’Association medicale canadienne PMID: 21844111

Kuk JL, Ardern CI, Church TS, Sharma AM, Padwal R, Sui X, & Blair SN (2011). Edmonton Obesity Staging System: association with weight history and mortality risk. Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme PMID: 21838602