DiaRem score: external validation

Abstract

Christopher Still and colleagues1 have produced a novel scoring system (DiaRem score) to predict the probability of remission of type 2 diabetes after Roux-en-Y gastric bypass (RYGB) surgery. Determination of predictive factors of diabetes remission after weight-loss surgery has been of great scientific and clinical interest to bariatric and metabolic surgeons for the past decade. In 2003, Schauer and colleages2 noted that patients with a longer preoperative duration of type 2 diabetes, advanced disease (ie, use of insulin), and lower weight loss after surgery were least likely to achieve resolution of type 2 diabetes after RYGB.2 Although several studies confirmed these findings, until now the presence of a valid, simple, and reproducible model to predict the outcome of type 2 diabetes after bariatric surgery and help decision making had not been reported. The DiaRem score, which is based on a retrospective study of 690 patients with diabetes (most were followed up for ≤2 years), was created using a Cox regression model, and four preoperative clinical variables were identified in the final scoring model: insulin use, age, HbA1c, and type of antidiabetic drugs used. On the basis of the DiaRem score (ranging from 0 to 22), patients were classified into five groups (table).1 Table Prediction of diabetes remission according to DiaRem score in Still and colleagues’ study compared with the Cleveland Clinic cohort Our team at the Cleveland Clinic recently published data on the long-term metabolic effects of bariatric surgery in a cohort of diabetic patients.3 Definitions of complete remission (HbA1c 5 years) clinical outcomes in a subgroup of 136 patients with type 2 diabetes who underwent RYGB during 2004–07, and had complete data for the four main preoperative predictive factors, to establish the external validity of the DiaRem scoring system. At 1–2 years after surgery, 71% of the Cleveland Clinic cohort had complete or partial remission of type 2 diabetes, and 49% achieved complete remission. These findings are compatible with Still and colleagues’ data (63% complete or partial remission, 49% complete remission). However, at a median of 6 years (range 5–9) after gastric bypass, 58% of the Cleveland Clinic cohort had complete or partial remission, and only 28% complete remission. Overall, the original data reported by Still and colleagues agree with data from the long-term Cleveland Clinic cohort, especially data for patients with low DiaRem scores (table). Similar to the original cohort, the proportion of patients achieving long-term diabetes remission in the Cleveland Clinic cohort was greatest for those with the lowest DiaRem scores, and least for those with the highest scores. However, when DiaRem scores are extremely high—ie, in the subgroup of patients who were on insulin at the time of surgery—we did not see strong agreement. This difference might be because the scoring system does not work well when DiaRem scores are extremely high, because a different patient population had been used, or simply because the sample size was insufficient in both the Cleveland Clinic cohort and the cohort used by Still and colleagues. Predictors of type 2 diabetes remission and recurrence in the Cleveland Clinic cohort were duration of type 2 diabetes and excess weight loss. Based on our analysis, the cutoff point of 5 years or less of diabetes duration was the best timepoint to predict remission (sensitivity 76%, specificity 79%, area under the receiver operating characteristic curve of 0·82). Patients with type 2 diabetes duration of 5 years or less had a 76% long-term remission rate (complete or partial) compared with 21% for patients with duration of type 2 diabetes of greater than 5 years.3 Data for preoperative duration of diabetes was not available in Still and colleagues’ study and was not included in multivariate analyses,1 which might be a limitation of this scoring system. Although several weight-independent mechanisms have been proposed, the main mechanism in long-term remission of type 2 diabetes after bariatric surgery is most likely weight loss. Notably, the extent of surgical weight loss was a statistically significant predictive factor for type 2 diabetes remission in several studies, including ours.2,3 We acknowledge that the model developed by Still and colleagues is based only on preoperative clinical criteria; nevertheless, such a model might not be complete without consideration of the extent of weight loss or regain after surgery. In conclusion, the DiaRem score seems a valid system for prediction of diabetes remission after RYGB surgery, especially in patients not taking insulin. Other factors such as duration of type 2 diabetes and extent of surgical weight loss are important and should be considered in clinical and research settings.