Individualized Metabolic Surgery Score: A New Nomogram for Procedure Selection Based on Diabetes Severity

An Interview with:

Ali Aminian, MD Ali Aminian, MD

Associate Professor of Surgery, Cleveland Clinic, Cleveland, Ohio

Developed from the largest reported cohort (n=900) with long-term postoperative glycemic follow-up, the Individualized Metabolic Surgery (IMS) Score is a new nomogram that classifies patients into three categories of diabetes severity—mild, moderate, and severe—and suggests which surgery type will provide the best balance between diabetes remission and procedure risk. The study included 650 patients from a single center in Cleveland, Ohio, and was then validated in a cohort of 250 patients at another single center in Barcelona, Spain. Study researchers concluded that in mild T2DM (IMS Score≤25), both Roux-en-y gastric bypass (RYGB) and sleeve gastrectomy (SG) significantly improve diabetes, and in severe T2DM (IMS Score>95), when there is limited beta-cell reserve/function, both procedures have similarly low efficacy in achieving diabetes remission. They also reported findings of an intermediate group in which RYGB is significantly more effective than SG, which they postulated was likely related to its more pronounced neurohormonal effects.

This month, we present an interview with Individualized Metabolic Surgery (IMS) Score study lead author Ali Aminian, MD, Associate Professor of Surgery at the Cleveland Clinic, Ohio, who presented these findings during the 137th meeting of the American Surgical Association, April 20 to 22, 2017, in Philadelphia, Pennsylvania.

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How did you determine the need to develop the Individualized Metabolic Surgery Score for patients with obesity and diabetes?

Dr. Aminian: One of the unanswered questions in the field of bariatric surgery was how to choose the appropriate procedure in an individual with type 2 diabetes mellitus (T2DM). Long-term response to bariatric surgery differs according to diabetes severity; a patient with mild disease (e.g., diabetes for one year, good glycemic control with metformin) is considerably different than a patient with severe disease (e.g., diabetes for 15 years, poor glycemic control while taking 3 medications including insulin). This study aimed to construct and externally validate an individualized scoring system for evidence-based selection of metabolic surgery for T2DM based on disease severity.

Would this score also be valid for patients with obesity without diabetes?

Dr. Aminian: No. The Individualized Metabolic Surgery (IMS) score guides bariatric procedure selection in patients with T2DM.

Does age play a role in your algorithm?

Dr. Aminian: No. Age at the time of surgery was not an independent predictor of long-term diabetes remission after gastric bypass and sleeve gastrectomy. Our model was developed to stage the severity of diabetes preoperatively based on four independent predictors of long-term diabetes remission, including Hemoglobin A1c (HbA1c), preoperative duration of diabetes, number of diabetes medications, and insulin use before surgery (Figure 1). These factors are readily available in clinical practice and can serve as a proxy to the functional pancreatic ß-cell reserve.

Were the surgical techniques used in Roux-en-y gastric bypass and sleeve gastrectomy the same when comparing the procedures performed in the United States and Spain?

Dr. Aminian: There are minor variations in surgical techniques around the world. However, these minor changes would not have significant effects on long-term diabetes response. Findings on diabetes remission in each subgroup were relatively comparable in the cohorts from Cleveland and Barcelona.

The number of patients who underwent SG is significantly lower than those who underwent RYGB. Please comment on whether this is relevant to the study’s conclusions.

Dr. Aminian: That is correct—the number of patients who underwent SG was significantly lower than those who underwent RYGB. While this study is the largest reported series of SG in diabetic patients with long-term glycemic outcome, the sample size is not as good as RYGB cases. Only a quarter of the Cleveland cohort underwent SG, which may impact the outcomes in these patients. However, similar findings were observed from the validation cohort (Barcelona’s cohort) where nearly half of the patients underwent SG.

In patients with mild diabetes (classification based on HbA1C, preoperative duration of T2DM, number of diabetes medications, and insulin use before surgery), would you still recommend RYGB over SG despite the outcomes being similar?

Dr. Aminian: According to our nomogram, diabetes is considered mild if the IMS score is ≤25 points. In these patients, both RYGB and SG were highly effective in the treatment of diabetes with significantly high long-term remission rates of 92 percent and 74 percent, respectively. This finding is not surprising as a mild disease is likely an indirect reflection of a less advanced diabetes associated with higher functional pancreatic ß-cell reserve. Thus, both metabolic procedures are highly effective and good options for patients with mild diabetes. Since RYGB resulted in better long-term diabetes remission rates and reduction in medications, we suggest it as the metabolic procedure of choice in those with mild diabetes if there is no other reason to favor SG.

Does this score also consider the potential for complications when making recommendations for surgery?

Dr. Aminian: Our model has been generated based on the long-term efficacy of surgical procedures and we did not analyze the complications on this study. Our recommendation for surgery in each subgroup is based on the assumption that SG is a less complicated procedure than RYGB. This has been shown in multiple studies.2 For patients with severe diabetes (IMS Score>95), both procedures have similarly low efficacy for diabetes remission. Thus, we suggest sleeve gastrectomy as the bariatric procedure of choice given better risk-benefit ratio. In mild diabetes (IMS Score≤25), both procedures significantly improve diabetes, yet if risk-benefit ratio permits, we suggest gastric bypass since it leads to higher long-term remission. There is an intermediate group, for whom Roux-en-Y gastric bypass is significantly more effective than sleeve gastrectomy in achieving long-term diabetes remission.

Where can readers access the IMS Score nomogram?

Dr. Aminian: The IMS online calculator (Figure 2) is accessible at http://riskcalc.org/Metabolic_Surgery_Score

References

1. Aminian A, Brethauer S, Andalib A, et al. Individualized Metabolic Surgery Score: Procedure Selection Based on Diabetes Severity. Presented at: 137th Annual Meeting of the American Surgical Association, Philadelphia, PA; April 20-22, 2017.

2. Hutter MM, Schirmer BD, Jones DB, et al. First report from the American College of Surgeons Bariatric Surgery Center Network: laparoscopic sleeve gastrectomy has morbidity and effectiveness positioned between the band and the bypass. Ann Surg. 2011;254(3):410–420.

Funding: No funding was provided in the preparation of this manuscript.

Financial disclosures: The authors report no conflicts of interest relevant to the content of this article. 

Tags: Metabolic surgery

Category: Interviews, Past Articles