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, announced Dr. Eric J. DeMaria of Duke University, Durham, N.C.
Use of the OS-MRS will provide for a more complete 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, he said.
Dr. DeMaria and coworkers developed the OS-MRS while he was at the Medical College of Virginia, Richmond, by analyzing prospectively collected data on 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, while 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 No. 1 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
Discussant Dr. Michael G. Sarr said bariatric surgery has been criticized in the press—“and potentially rightfully so”—because of its lack of accountability.
“The lack of a valid and predictive risk adjustment score has hampered the interpretation of outcomes in bariatric surgery tremendously over the last decade,” added Dr. Sarr, professor of surgery and chair of the division of general and GI surgery at the Mayo Clinic, Rochester, Minn.
Like others in the audience, he said the OS-MRS might have even greater predictive strength if it incorporated weighted scoring of the risk factors. Also, he continued, he'd like a scoring system that predicted major morbidity, not just mortality.
Dr. DeMaria said he deliberately steered clear of weighted scoring for the OS-MRS. “It's a clinically useful scoring system primarily due to its simplicity. It's so simple that it can allow bedside use and therefore may have utility along the lines of the Child-Pugh classification, which is still used by many surgeons when looking at liver disease today.”
A risk score that also predicts postop major morbidity is in the works, he added. Dr. DeMaria will soon gain access to the American College of Surgeons' National Surgical Quality Improvement Program database, which might identify new variables that completely redefine risk stratification in bariatric surgery.
All papers presented at the 127th annual meeting of the ASA are subsequently submitted to the Annals of Surgery for consideration.
'It's a clinically useful scoring system primarily due to its simplicity.' DR. DEMARIA