Red cell distribution width: A novel biomarker for the prediction of one-year excess body-mass index loss following laparoscopic Roux-en-Y gastric bypass

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

Introduction:

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).

Methods:

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.

Results:

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).

Conclusions:

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.