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Background: The bioelectrical impedance (BI) phase angle (PA), analyzed directly through BI analysis (BIA), is determined by tissue cellularity, representing a direct measure of cellular stability and, for this reason, has been studied and considered as an indicator of prognosis and nutrition status in adults and children. Objective: We aimed to determine if PA can be an indicator of mortality and prognosis in newborns admitted to the neonatal intensive care unit (NICU). Methods: Transversal study conducted at a public NICU in Curitiba, Paraná, Brazil. All newborns, preterm and term, were considered eligible for the study if admission to the NICU occurred by the first hour of life. The Score for Neonatal Acute Physiology II, as well as the Perinatal Extension version, were developed to assess the risk of mortality for all newborns, measured within 12 hours of admission. BIA measurements were conducted using the tetrapolar BioScan Maltron 916, with single‐frequency (50 kHz) tetrapolar BI. PA was calculated as the arc tangent: (Xc/R) x 180°/π. Results: BIA was measured during the first 24 hours of admission for all newborns (n = 93), repeated between 24 and 48 hours (n = 79) and again after 7 days (n = 55), always when possible. PA measurements decreased in the first 48 hours in premature newborns, particularly among those who died. The premature newborns also showed a significant decrease from the first to the last PA measurement (P =.001). In addition, whereas full‐term newborns showed an increase of PA at 1 week of life, preterm infants continued to have a decrease in values. For preterm newborns, PA measurements decreased and more sharply so for those who died. This result should be viewed with caution given the small number of deaths, but it should be investigated to understand the role of PA in the prognosis of NICU newborns. Conclusions: The absolute value of PA during the first 24 hours of life was not a good marker for severity or mortality. However, the decrease of PA between different moments of evaluation was a good marker of severity. The decrease of PA in the first 48 hours in premature newborns, and that when the decrease is more pronounced, may be indicative of mortality. The difference in PA values between these newborns is probably a significant variable for mortality and prognosis and not a cutoff value. [ABSTRACT FROM AUTHOR]

Background and purpose: There is a growing body of evidence indicating that phase angle (PhA) can be used as an indicator of nutritional status, disease prognosis, and mortality risk; however, it is still unknown whether PhA can be used as an explanator of functional capacity and muscle quality in older women. The main purpose of this cross-sectional study was to explore whether PhA is associated with muscle quality and functional capacity in older women, regardless of total and regional body composition. Methods: A total of 125 older women-66.7 (4.7) years; 65.6 (10.9) kg body mass; 156.1 (5.2) cm height; 26.9 (4.0) kg/m body mass index-participated in this study. Anthropometric, PhA, body composition (whole-body dual-energy x-ray absorptiometry) and muscle quality (defined as total muscular strength per kilogram of appendicular lean soft tissue) were measured. The functional capacity was assessed by 4 tests: 10-m walk test, rising from sitting position, rising from ventral decubitus position, and rising from a chair and walking around the house. The summing z-scores for the 4 tests was used as a continuous functional capacity score. Linear regression analysis was conducted to test whether PhA is related to the dependent variables (muscle quality and functional capacity), after adjusting for potential covariates. Results: The PhA presented a small-to-moderate relationship with muscle quality (r = 0.27; P < .01) and functional capacity (r = 0.31; P < .01), respectively. These relationships remained significant after adjustment for age, lower limb lean soft tissue, and total fat mass for muscle quality (β= 0.55; P < .01) and functional capacity (β= 1.38; P < .01). Conclusion: Our findings suggest that healthy elderly women with higher values of PhA have a better muscle quality and functionality, regardless of age and body composition. [ABSTRACT FROM AUTHOR]

Background: The potential effect of bariatric surgery on weight reduction and improvement of associated comorbidities is known, but the ratio obtained between the components of body weight, including lean body mass, body fat mass, and bone mass, is still not determined. This study aims to verify the changes in body composition during the first year after bariatric surgery. Methods: We conducted a prospective observational cohort study. Fifty patients who underwent bariatric surgery and maintained follow-ups were selected. Patients were assessed preoperatively and postoperatively for periods of 1, 3, 6, and 12 months using tetrapolar bioelectrical impedance analysis and laboratory testing of lipids and serum albumin levels. Data were statistically analyzed. Results: Statistically significant differences (p < 0.001) were obtained between the preoperative and 12-month evaluation respectively, for body mass index (BMI) (45.8 ± 7.5 to 30.0 ± 4.8 kg/m2), FM (64.7 ± 15.5 to 30.6 ± 9.8 kg), PFM (51.6 ± 4.17 to 37.3 ± 7.6%), and total cholesterol levels (197.1 ± 49.8 to 169.8 ± 31.0 mg/dL). The decrease in PFM shows a better proportion between the body components. PFM showed significantly higher decrease in males than in females (p = 0.012). Lean body mass (p = 0.000) reduction was highest for patients operated by the Unified Health System (SUS, Government of Brazil) probably because of its few financial resources to maintain postoperative care. Conclusion: The change in body composition of patients who underwent Roux-en-Y gastric bypass was statistically significant for all variables examined during the first year postoperatively. This shows the effectiveness of the surgical procedure and clinical protocol set, which tends to favor a better health prognosis and weight maintenance in the long term. [ABSTRACT FROM AUTHOR]

Introduction: Bioelectrical impedance analysis (BIA) is a practical and rapid method for making a longitudinal analysis of changes in body composition. However, most BIA validation studies have been performed in a clinical population and only at one moment, or point in time (cross-sectional study). The aim of this study is to investigate the accuracy of predictive equations based on BIA with regard to the changes in fat-free mass (FFM) in Brazilian male army cadets after 7 mo of military training. The values used were determined using dual-energy X-ray absorptiometry (DXA) as a reference method.Materials and Methods: The study included 310 male Brazilian Army cadets (aged 17-24 yr). FFM was measured using eight general predictive BIA equations, with one equation specifically applied to this population sample, and the values were compared with results obtained using DXA. The student's t-test, adjusted coefficient of determination (R2), standard error of estimation (SEE), Lin's approach, and the Bland-Altman test were used to determine the accuracy of the predictive BIA equations used to estimate FFM in this population and between the two moments (pre- and post-moment).Results: The FFM measured using the nine predictive BIA equations, and determined using DXA at the post-moment, showed a significant increase when compared with the pre-moment (p < 0.05). All nine predictive BIA equations were able to detect FFM changes in the army cadets between the two moments in a very similar way to the reference method (DXA). However, only the one BIA equation specific to this population showed no significant differences in the FFM estimation between DXA at pre- and post-moment of military routine. All predictive BIA equations showed large limits of agreement using the Bland-Altman approach.Conclusion: The eight general predictive BIA equations used in this study were not found to be valid for analyzing the FFM changes in the Brazilian male army cadets, after a period of approximately 7 mo of military training. Although the BIA equation specific to this population is dependent on the amount of FFM, it appears to be a good alternative to DXA for assessing FFM in Brazilian male army cadets. [ABSTRACT FROM AUTHOR]

Background The body adiposity index ( BAI) comprises a simple method for estimating body fat ( BF) that needs to be validated in patients with severe obesity. The present study aimed to determine BAI accuracy with respect to the determination BF in patients with severe obesity. Methods A cross-sectional prospective study comparing two methods for BF estimation was conducted in 433 patients with severe obesity between August 2012 to December 2014. BF was estimated by bioelectrical impedance analysis ( BIA) with specific equations developed for BF estimation in patients with severe obesity and BAI. The BF estimation in 240 patients with severe obesity (Group 1: G1) was used to evaluate BAI limitations and to develop a specific equation in this population. The new equation proposed was validated in another 158 patients with severe obesity (Group 2: G2). Results There was a significant difference between BF determination by BIA and BAI ( P = 0.039). The mean ( SD) BF in G1 was 52.3% (6.1%) determined by BIA and 51.6% (8.1%) determined by BAI. Sex, waist-hip ratio ( WHR) and obesity grade determined significant errors on BF estimation by BAI. A new equation (modified body adiposity index; MBAI) was developed by linear regression to minimise these errors [ MBAI% = 23.6 + 0.5 × ( BAI); add 2.2 if body mass index ≥ 50 kg m-2 and 2.4 if WHR ≥ 1.05]. The new equation reduced the difference [1.2% (5.9%), P < 0.001 to 0.4% (4.12%), P = 0.315] and improved the correlation (0.6-0.7) between methods. Conclusions BAI present significant limitations in severe obesity and MBAI was effective for BF estimation in this population. [ABSTRACT FROM AUTHOR]

Abstract: Background: Nutritional risk and malnutrition are highly prevalent among hospitalized patients. As a result, several methods have been developed to produce an adequate nutritional diagnosis. Objective: We aimed to assess the relationship between nutritional risk tools and parameters derived from bioelectrical impedance analysis with a Subjective Global Assessment (SGA). Design: A cross-sectional study was conducted from April to September 2010. Participants/setting: The study included 124 patients admitted to the Surgical Clinic I, University Hospital, Federal University of Santa Catarina, Florianópolis, Brazil, to undergo elective surgery. Main outcome measures: We utilized SGA and Nutritional Risk Screening 2002 (NRS 2002), Nutritional Risk Index (NRI), Fat-Free Mass Index (FFMI), Fat Mass Index (FMI), body cell mass as a percentage of the total weight (%BCM), and standardized phase angle (SPA). Statistical analysis performed: The agreement was tested by κ coefficient, while bivariate associations were tested by Mann-Whitney U test. Results: Prevalence of nutritional risk by NRS 2002 and NRI or malnutrition by SGA, FFMI, FMI, %BCM, and SPA was 19.3%, 69.5%, 35.5%, 12.9%, 8.1%, 46.8%, and 4.8%, respectively. The best agreement was between SGA and NRS 2002 (κ=.490), possibly because they constitute similar instruments. Patients identified as malnourished by SGA (B+C) showed considerably lower values of FFMI, FMI, BCM, and SPA. Conclusions: The results suggest that the NRS 2002 and parameters derived from bioelectrical impedance analysis identify patients with impaired nutritional status. [Copyright &y& Elsevier]

Objective: To review the technical aspects of body composition assessment by dual-energy X-ray absorptiometry (DXA) and other methods based on the most recent scientific evidence., Materials and Methods: This Official Position is a result of efforts by the Scientific Committee of the Brazilian Association of Bone Assessment and Metabolism (Associação Brasileira de Avaliação Óssea e Osteometabolismo, ABRASSO) and health care professionals with expertise in body composition assessment who were invited to contribute to the preparation of this document. The authors searched current databases for relevant publications. In this first part of the Official Position, the authors discuss the different methods and parameters used for body composition assessment, general principles of DXA, and aspects of the acquisition and analysis of DXA scans., Conclusion: Considering aspects of accuracy, precision, cost, duration, and ability to evaluate all three compartments, DXA is considered the gold-standard method for body composition assessment, particularly for the evaluation of fat mass. In order to ensure reliable, adequate, and reproducible DXA reports, great attention is required regarding quality control procedures, preparation, removal of external artifacts, imaging acquisition, and data analysis and interpretation., (© 2022. The Author(s).)

Objectives: The aims of this study were to evaluate the effect of biological maturity on body composition in Brazilian adolescent athletes, to verify the accuracy of previous bioimpedance predictive equations for estimating fat-free mass (FFM), and to develop new predictive equations, considering sexual and skeletal maturity., Methods: There were 318 Brazilian adolescent athletes (52% male) involved in this study. FFM was determined using single-frequency (50 kHz) bioelectrical impedance analysis (BIA) and dual-energy x-ray absorptiometry (DXA), which was used as the reference method. The adolescents were classified into skeletally mature using bone age (both sexes), and sexually mature using menarche occurrence (female). The effect of maturity on bioelectrical values was tested using bioelectrical impedance vector analysis. Three predictive BIA equations to estimate FFM were selected from the reviewed literature. Lin's concordance correlation coefficient and Bland-Altman test were used to test the concordance and accuracy of BIA equations. Stepwise multiple regression was used to develop new predictive equations, considering BIA vectors, age, skeletal, and sexual maturity., Results: DXA and BIA results showed wide limits of disagreement for FFM for all the three equations. Two new equation models were developed, including age and skeletal maturity for both sexes and menarche status for females. Both models showed high R 2 (males = 0.92 and females = 0.84)., Conclusions: The assessment of body composition in adolescent athletes should consider sexual (female) or skeletal (male) maturity. The newly proposed equations showed promising results in Brazilian adolescent athletes. A test in different groups and populations is necessary to evaluate the general suitability of the equations in adolescents., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background & Aims: The state of hyperhydration in critically ill patients with acute kidney injury (AKI) is associated with increased mortality. Bioelectrical impedance vector analysis (BIVA) appears to be a viable method to access the fluid status of critical patients but has never been evaluated in critical patients with AKI. The objective of this study is to evaluate the hydration status measured using BIVA in critical patients under intensive care at the time of AKI diagnosis and to correlate this measurement with mortality., Methods: We assessed the fluid status measured using BIVA in 224 critical patients at the time of AKI diagnosis and correlated it with mortality. To interpret the results, BIVA Software 2002 was used to plot the data from the patients studied on the 95% confidence ellipses of the RX c plane for comparisons between groups (non-survivors, survivors). Variables such as mechanical ventilation, vasoactive drug, and sepsis, among others, were collected., Results: The impedance vector analysis conducted using BIVA Software 2002 indicated changes in the body compositions of patients according to the 95% confidence ellipse between the vectors R/H and X c /H of the group of survivors and the group of deceased patients. Hotelling's test (T 2  = 21.2) and the F test (F = 10.6) revealed significant differences (p < 0.001) between the two groups. These results demonstrate that patients who died presented with a greater hydration volume at the time of AKI diagnosis compared with those who survived. In addition to the hydration status measured using BIVA, the following were also correlated with death: diagnosis at hospitalization, APACHE II score, length of hospital stay, RIFLE score, maximum organ failure, sepsis type, hemoglobin, and AF., Conclusions: The fluid status assessment measured using BIVA significantly demonstrated the difference in hydration between survivors and non-survivors among critically ill patients with AKI., (Copyright © 2017 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.)