Calculator Predicts Events With or Without Weight Loss Surgery

Marlene Busko

November 06, 2019

LAS VEGAS — Researchers have developed a calculator to predict the 10-year risk of a major cardiovascular event (MACE) or death in those with type 2 diabetes and obesity, depending on whether or not the patient decides to undergo bariatric surgery.

The risk calculator is available on the Cleveland Clinic website and will soon be available as an app (BariatricCalc), Ali Aminian, MD, a bariatric surgeon at the clinic, explained here at Obesity Week 2019.

The calculator requires the input of 26 patient variables and quantifies outcomes for the two scenarios (with or without metabolic surgery).

"Now you have two numbers, two values, that you can compare to see which way you want to go," Aminian told Medscape Medical News.

The predictor shows, he said, that "weight loss, diabetes remission, improvement in blood pressure, cholesterol, and cardiometabolic risk factors" that are seen with metabolic surgery "are going to have a significant impact to lower the risk of heart attacks, stroke, heart failure, kidney failure, and mortality."

It also indicates the likelihood of complications from surgery for a given patient.

Aminian said the calculator "can provide a glimpse into the future for individuals with diabetes and obesity, and demonstrate the impact usual medical care versus metabolic surgery would have on their risk of death or major complications."

This will "better inform treatment decisions and doctor recommendations and hopefully lead to improved patient care and outcomes," he added. 

Invited to comment, Oliver A. Varban, MD, also a bariatric surgeon, told Medscape Medical News: "These calculators are very important."

Surgical practices have accumulated this type of risk data, noted Varban, of the University of Michigan, Ann Arbor, whereas this kind of knowledge, or data, isn't available from primary care physicians or endocrinologists who've been treating obesity medically, he said.

"In Michigan, we have a similar risk calculator that looks at both weight loss outcomes and complication rates, and it's specific to procedure [eg, gastric bypass, sleeve]," Varban noted.

Clinicians can use the risk calculator for every patient. "We say, 'based on people who are similar to you, we can compare these operations,'" and find out potential complications and weight loss.

Few Qualifying Patients Have Metabolic Surgery

Despite the reported benefits of metabolic surgery, less than 1% of eligible patients undergo surgery, Aminian told delegates at Obesity Week, possibly partly because of a lack of knowledge about potential outcomes.

To address this knowledge gap, Aminian and his research team developed their risk calculator for patients with type 2 diabetes and obesity.

They first identified 288,692 patients with type 2 diabetes seen in the Cleveland Clinic Health System in 2004-2017.

Of these, 2287 patients with obesity (BMI ≥ 30 kg/m2) who underwent bariatric surgery were each matched with five patients, resulting in 11 435 control patients who received usual care.

Aminian presented results from the case-control study at the recent European Society of Cardiology Congress 2019, World Congress of Cardiology, which were simultaneously published in JAMA, as previously reported by Medscape Medical News. The study was sponsored by Medtronic.

The calculator was developed from a predictive model based on the study results.

In the surgery group, 63% of patients had gastric bypass, 32% had sleeve gastrectomy, and 5% had gastric banding.

The team then explored 26 risk factors for the different outcomes, including risk of death, in this large group of patients. Machine learning and traditional statistical techniques were used to identify the most accurate prediction models for each outcome and these were built into the calculator.

The risk calculator therefore requires the following inputs.

  • Demographics: Age, sex, body mass index, race, smoking status.

  • Medical history: Hypertension, dyslipidemia, chronic obstructive pulmonary disease, heart failure, coronary artery disease, cerebrovascular disease, diabetic neuropathy, peripheral arterial disease, nephropathy (diabetic kidney disease), dialysis.

  • Clinical and lab data: A1c (%), systolic and diastolic blood pressure (mm Hg), creatinine (mg/dL), triglycerides (mg/dL).

  • Current medications: Insulin, other diabetes medication (noninsulin), lipid-lowering medication, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, other antihypertensive medications, aspirin, warfarin.

Personalized, Evidence-Based Risk Information for Patients

To illustrate how it works, Aminian entered values for a hypothetical patient into the online risk calculator.

It showed that if this patient continued along the same medical treatment path, they had a predicted 10-year risk of dying of 6.6%, but if they underwent metabolic surgery, this would drop to 3.7%.  

Study limitations included potential coding errors and a lack of data for relevant variables (such as duration of diabetes and family history of coronary artery disease).

Researchers also did not compare outcomes after the different types of bariatric surgery and the model was not validated in an external cohort.

And less than 10% of patients in the medical group were receiving GLP-1 agonists or SGLT2 inhibitors (which are cardioprotective) in the case-control study that was used to estimate risk, so if a clinician has a patient in front of them who is using these newer medications for type 2 diabetes, the calculator may overestimate their cardiovascular risk.

However, "the reality is" that those medications are still not available to everybody because of their cost, said Aminian.

Despite these limitations, the risk score "can provide personalized evidence-based risk information for patients with type 2 diabetes and obesity," he asserted.

The researchers now plan to test the risk calculator in a randomized controlled trial, to see if its use would change patient decisions and patient perceptions about the surgery.

Obesity Week 2019. Presented November 5, 2019.

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