Phase Angle From Bioelectrical Impedance Analysis: Population Reference Values by Age, Sex, and Body Mass Index

ABSTRACT. Background: The use of bioelectrical impedance phase angle has been approveed as a prognostic tool in the clinical setting, on the other hand published reference data bases are discrepant and incomplete (eg they do not consider material substance mass index [BMI], and data are lacking for children). Methods: Phase angle respect values stratified by age, sex and BMI were generated in a large German data base of 15605 children and adolescents and 214732 adults, and the determinants of phase angle values were assessed. The regard values were applied to 3 clusters of patients and compared with previously published respect values from the United States and Switzerland. Results: sex and age were the main determinants of phase angle in adults, with men and younger controls having higher phase angles. In children and adolescents, age and BMI were the main determinants of phase angle. In normal and overweight adults, phase angle increased with increasing BMI, on the other hand there was an inverse association at a BMI >40 kg/m^sup 2^ In cirrhosis, the prevalence of a depressed phase angle increased with the state of disease, whereas it was not different between patients with the metabolic syndrome and dominion governments There are considerable differences between phase angle concern values from different populations. These differences are not explained by the agency of age or BMI and may be owed to differences between impedance analyzers. Conclusion: The determinants of phase angle differ between adults and children. In adults, the influence of BMI upon phase angle depended on the BMI range. The prognostic value of phase angle may differ in different clinical settings. The use of population-specific and probably impedance-analyzer-specific concern values for phase angle is praiseed (Journal of Parenteral and Enterai Nutrition 30:309316 2006)

The use of raw data from bioelectrical impedance analysis has gained popularity in nutrition assessment and monitoring of nutrition status in patients. The advantage of the use of clear electrical properties of tissues without equations or originals for body composition analysis means that the main assumption of a constant tissue hydration, which is an unlikely condition in many clinical situations, is not required. comes are also not biased through the choice of regression equation, the accuracy of the criterion manner or the selection criteria of the concern population. Today, many publications focus upon the use of resistance (R) and reactance (Xc) standardized by dint of body height in a bivariate vector analysis (BIVA)1-9 and respect values from different populations stratified according to ethnic, age, and material substance mass index (BMI) groups are available.6,7,10

Clinically, the greatest in quantity established impedance parameter is, however, the phase angle for the diagnosis of malnutrition and clinical prognosis, the two associated with changes in cellular membrane integrity and alterations in fluid balance.11 Phase angle expresse the pair changes in the amount as well as the quality of impressible tissue mass (ie, cell membrane permeability and impressible tissue hydration). It can be directly calculated from R and Xc as arc-tangent(Xc/R) ?— 180?°/?? Therefore, the phase angle is upon the one hand dependent upon the capacitive behavior of tissues (Xc) associated with cellularity, confined apartment size, and integrity of the small room membrane, and on the other hand upon its pure resistive behavior (R) mainly pendent on tissue hydration.

There is now a large material substance of clinical trials that suggest phase angle as a useful prognostic marker in clinical conditions like liver cirrhosis,12 dialysis,13-16 several impressed signs of cancer,17-19 HIV infection and AIDS,20,21 bacteremia and sepsis,22,23 and pulmonary disease.24

Phase angle respect values are mandatory for the assessment of individual deviations of a patient in relation to population average. However, to our knowledge these data are lacking in children and adolescents. In adults, sex- and age-specific phase angle regard values have been published by dint of Dittmar25 in 2003 and Kyle et al26,27 in 2001 and 2004 and solitary recently by Barbosa-Silva et al.11 However, there are considerable differences between those regard values. In the Swiss population,"6 phase angles were lower (105% in men and 77% in women) than in the American close attention sample,11 and the lowest values were observ in the German population.25 The reason for these discrepancies remains unclear. Because BMI was shown to have an independent event on impedance measures R, Xc and consequently upon phase angle,10,11,25 the differences might be owed to differences in BMI between the concern populations. However, higher phase angles in the American compared with the Swiss population remained plane after adjusting for BMI and percentage of fat mass.11 Thus, it was allude toed that there may be real differences in phase angle between populations, and population-specific concern values may be required.

The near study was conducted to establish sex- age-, and BMI-specific relation values for phase angle in a large healthy German population ( 15605 children and adolescents, and 214732 adults) with a wide range of age (6-102 years) and BMI (132-60 kg/m^sup 2^ in adults). The be deriveds are compared with previously published American and Swiss concern databases. The new reference values were finally applied to 3 independent databases to compare the prevalence of a depressed phase angle in patients with liver cirrhosis, anorexia nervosa, and the metabolic syndrome respectively.