Bioimpedance phase angle is associated with serum transthyretin but not with prognostic inflammatory and nutritional index during follow-up of women submitted to bariatric surgery

Abstract

Background & aims: Phase angle (PhA) has been used as a prognostic indicator in several clinical situations. However, the use of PhA as a prognostic tool in bariatric patients is less known. The aim of this study was to evaluate PhA as a prognostic index and its correlation with the prognostic inflammatory and nutritional index (PINI) during follow-up of women subjected to bariatric surgery.

Methods: Twenty female volunteers were studied. Body weight, body mass index (BMI), PhA, and biochemical components of PINI [serum C-reactive protein, alpha-1-acid glycoprotein, albumin, and transthyretin (TTR) concentrations] were evaluated at three time points: before (T0) and approximately 2-3 (T1) and 6 (T2) months after surgery. One-way repeated measures ANOVA or the Friedman test with Tukey's post hoc test was used depending on data normality. The associations between PhA and the other parameters were evaluated using Spearman's (nonparametric data) or Pearson's (parametric data) correlation coefficient.

Results: Phase angle reduction was accompanied by a significant decrease in body weight and BMI at T1 (P < 0.05), but not at T2 (P > 0.05). PINI indicated low-risk complications during the preoperative period and no risk during the postoperative period (T1 and T2). No significant correlation was observed between PhA and PINI (P > 0.05). Regarding its association with the biochemical components of PINI, lower PhA values were significantly correlated with lower serum TTR concentrations (r = 0.633, P < 0.001).

Conclusions: Phase angle was not associated with PINI, although lower values were correlated with lower serum TTR, suggesting that PhA reduction is associated with an increased nutritional risk.

Keywords: Malnutrition; Obesity; Weight loss.