Eric S Wise, MD1, Kyle M Hocking, PhD2, Adam Weltz, MD3, Anna Uebele, MD3, Jose J Diaz, MD, CNS, FACS, FCCM3, Stephen M Kavic, MD3, Mark D Kligman, MD3. 1Vanderbilt University Dept of Surgery; University of Maryland Dept of Surgery, 2Vanderbilt University Dept of Surgery, 3University of Maryland Dept of Surgery
Bariatric surgery is the most effective method for producing sustained weight loss and improving weight-associated comorbidities in the morbidly obese population. The Roux-en-Y gastric bypass is among the most common and effective operations available, and is routinely performed laparoscopically. The red cell distribution width (RDW), a marker of size dispersion of circulating erythrocytes, is an emerging marker of inflammation usually reported as part of the routinely obtained pre-operative complete blood count. In this study, we tested our hypothesis that RDW represents a biomarker independently predictive of excess body-mass index loss (EBMIL) following laparoscopic Roux-en-Y gastric bypass (LRYGB).
Five hundred and forty-seven included LRYGB patients from a single institution were individually reviewed, noting both pre-operative RDW and percent excess BMI loss at six months and one year post-LRYGB (%EBMIL180 and %EBMIL365, respectively). Bivariate and multivariate linear regression analysis was conducted between age, gender, initial body-mass index (BMI0) and RDW and each of the two endpoints, to assess the independence of RDW as a predictor of post-operative success.
The median RDW was 13.9 (13.3 – 14.6)%, and median EBMIL180 and EBMIL365 were 55.4 (45.2 – 66.7)% and 71.3 (58.9 – 87.8)%, respectively. Upon bivariate linear regression analysis, both BMI0 (B = -1.1 [-1.2 – -1.0]%, P < .001) and RDW (B = -3.4 [-4.6 – -2.2]%, P < .001) were significantly associated with %EBMIL180, while male gender (B = -8.9 [-13.2 – -4.6]%, P < .001), BMI0 (B = -1.4 [-1.5 – -1.2]%, P < .001) and RDW (B = -4.6 [-6.2 – -3.0]%, P < .001) were significantly associated with %EBMIL365. After controlling for age, gender and BMI0, RDW was independently associated with EBMIL365 (B = -1.4 [-2.8 – -0.002]%, P = .05), but not EBMIL180 (B = -0.6 [-1.6 – 0.5]%, P = .30. Upon Kruskal-Wallis analysis, patients with a pre-operative RDW > 15.0% had significantly lower %EBMIL than those in the <13.0% (***P < .001) and 13.0-15.0% (**P < .01) strata (Figure 1).
RDW is independently predictive of EBMIL at one year following LRYGB. This represents a novel, inexpensive and readily available pre-operative biomarker that may provide clinically useful prognostic information for the patient and bariatric care team.