COLORADO SPRINGS — Development of the first validated risk scoring system in bariatric surgery is anticipated to bring some much-needed accountability to the field, according to speakers at the annual meeting of the American Surgical Association.
The Obesity Surgery Mortality Risk Score (OS-MRS) is an easy-to-use system that effectively stratified risk in its validation study of 4,431 consecutive bariatric surgery patients at four university medical centers, said Dr. Eric J. DeMaria of Duke University, Durham, N.C.: Use of the OS-MRS will provide for a more comprehensive and individualized informed consent process; assist insurance companies and centers-of-excellence programs in their surgeon credentialing efforts; and encourage development of testable surgical risk reduction strategies.
Dr. DeMaria and coworkers developed the OS-MRS while he was at the Medical College of Virginia, Richmond, by analyzing prospectively collected data from 2,075 consecutive patients undergoing gastric bypass surgery. Using multivariate analysis, they identified five independent predictors of 90-day mortality: a body mass index of 50 kg/m
The investigators assigned one point to each of the five preoperative risk factors. Patients with a score of 0–1 were rated class A, lowest risk. A score of 2–3 earned a class B ranking, and 4–5 points conferred class C, high risk.
Ninety-day mortality in the validation study was 0.7%. A total of 25 of the deaths occurred within 30 days after surgery. Pulmonary embolism was the main cause of mortality, accounting for 10 of the 33 postoperative deaths.
Mortality in the 2,166 patients who were class A by the OS-MRS was 0.2%, compared with 1.2% in the 2,140 class B patients and 2.4% in the 125 class C patients. Each of these differences was statistically significant.
A preoperative BMI of at least 50 kg/m
“The lack of a valid and predictive risk adjustment score has hampered the interpretation of outcomes in bariatric surgery tremendously over the last decade,” said discussant Dr. Michael G. Sarr, professor of surgery and chair of the division of general and GI surgery at the Mayo Clinic, Rochester, Minn. The OS-MRS might have even greater predictive strength if it incorporated weighted scoring of the risk factors, he commented, noting that a scoring system that predicted major morbidity, not just mortality, would also be useful.
Dr. DeMaria said he deliberately avoided using weighted scoring. “It's a clinically useful scoring system primarily due to its simplicity, 'he said, adding that a risk score that also predicts postop major morbidity is in the works.