In vivo neutron activation analysis. Clinical potential in body composition studies

Comparison of body composition assessment methods in pediatric intestinal failure

OBJECTIVES

The aim of the study was to examine the agreement of multifrequency bioelectric impedance analysis (BIA) and anthropometry with reference methods for body composition assessment in children with intestinal failure (IF).

METHODS

We conducted a prospective pilot study in children 14 years or younger with IF resulting from either short bowel syndrome or motility disorders. Bland-Altman analysis was used to examine the agreement between BIA and deuterium dilution in measuring total body water (TBW) and lean body mass (LBM), and between BIA and dual-energy x-ray absorptiometry (DXA) techniques in measuring LBM and fat mass (FM). FM and percent body fat (%BF) measurements by BIA and anthropometry were also compared in relation to those measured by deuterium dilution.

RESULTS

Fifteen children with IF, median (interquartile range) age 7.2 (5.0, 10.0) years, and 10 (67%) boys, were studied. BIA and deuterium dilution were in good agreement with a mean bias (limits of agreement) of 0.9 (-3.2 to 5.0) for TBW (L) and 0.1 (-5.4 to 5.6) for LBM (kg) measurements. The mean bias (limits) for FM (kg) and %BF measurements were 0.4 (-3.8 to 4.6) kg and 1.7 (-16.9 to 20.3)%, respectively. The limits of agreement were within 1 standard deviation of the mean bias in 12 of 14 (86%) subjects for TBW and LBM, and in 11 of 14 (79%) for FM and %BF measurements. Mean bias (limits) for LBM (kg) and FM (kg) between BIA and DXA were 1.6 (-3.0 to 6.3) kg and -0.1 (-3.2 to 3.1) kg, respectively. Mean bias (limits) for FM (kg) and %BF between anthropometry and deuterium dilution were 0.2 (-4.2 to 4.6) and -0.2 (-19.5 to 19.1), respectively. The limits of agreement were within 1 standard deviation of the mean bias in 10 of 14 (71%) subjects.

CONCLUSIONS

In children with IF, TBW and LBM measurements by multifrequency BIA method were in agreement with isotope dilution and DXA methods, with small mean bias and clinically acceptable limits of agreement. In comparison with deuterium dilution, BIA was comparable to anthropometry for FM and %BF assessments with small mean bias, but the limits of agreement were large. BIA is a reliable method for TBW and LBM assessments in population studies; however, its reliability in individual patients, especially for FM assessments, cannot be guaranteed.

Sarcopenia: an undiagnosed condition in older adults. Current consensus definition: prevalence, etiology, and consequences. International working group on sarcopenia

Sarcopenia, the age-associated loss of skeletal muscle mass and function, has considerable societal consequences for the development of frailty, disability, and health care planning. A group of geriatricians and scientists from academia and industry met in Rome, Italy, on November 18, 2009, to arrive at a consensus definition of sarcopenia. The current consensus definition was approved unanimously by the meeting participants and is as follows: Sarcopenia is defined as the age-associated loss of skeletal muscle mass and function. The causes of sarcopenia are multifactorial and can include disuse, altered endocrine function, chronic diseases, inflammation, insulin resistance, and nutritional deficiencies. Although cachexia may be a component of sarcopenia, the 2 conditions are not the same. The diagnosis of sarcopenia should be considered in all older patients who present with observed declines in physical function, strength, or overall health. Sarcopenia should specifically be considered in patients who are bedridden, cannot independently rise from a chair, or who have a measured gait speed less that 1 m/s(-1). Patients who meet these criteria should further undergo body composition assessment using dual energy x-ray absorptiometry with sarcopenia being defined using currently validated definitions. A diagnosis of sarcopenia is consistent with a gait speed of less than 1 m·s(-1) and an objectively measured low muscle mass (eg, appendicular mass relative to ht(2) that is ≤ 7.23 kg/m(2) in men and ≤ 5.67 kg/m(2) in women). Sarcopenia is a highly prevalent condition in older persons that leads to disability, hospitalization, and death.

Nutritional deficiencies during critical illness

A significant proportion of critically ill children admitted to the pediatric intensive care unit (PICU) present with nutritional deficiencies. Malnourished hospitalized patients have a higher rate of complications, increased mortality, longer length of hospital stay, and increased hospital costs. Critical illness may further contribute to nutritional deteriorate with poor outcomes. Younger age, longer duration of PICU stay, congenital heart disease, burn injury, and need for mechanical ventilation support are some of the factors that are associated with worse nutritional deficiencies. Failure to estimate energy requirements accurately, barriers to bedside delivery of nutrients, and reluctance to perform regular nutritional assessments are responsible for the persistence and delayed detection of malnutrition in this cohort.

Benefits of exercise and dietary measures to optimize shifts in body composition with age

Ageing is associated with changes in body composition, including an increase and redistribution of adipose tissue and a decrease in muscle and bone mass, beginning as early as the fourth decade of life. These changes have significant implications for the health and functioning of the individual because of their associations with chronic disease expression and severity, as well as geriatric syndromes such as mobility impairment, falls, frailty and functional decline. Therefore, understanding the preventive and therapeutic options for optimizing body composition in old age is central to the care of patients in mid-life and beyond. Pharmacological interventions are currently available for maintaining or improving bone mass, and much current interest is focused on anabolic agents that will preserve or restore muscle mass, as well as those that can potentially limit adipose tissue deposition. However, in this brief review, non-pharmacological modulation of body composition through appropriate dietary intake and physical activity patterns, will be discussed. There is sufficient evidence currently to suggest that a substantial portion of what have been considered 'age-related' changes in muscle, fat and bone are in fact related either to excess energy consumption, decreased energy expenditure in physical activity, or both factors in combination. In addition, selective underconsumption of certain macro- or micronutrients contributes to losses of muscle and bone mass. Each of the three compartments will be considered in turn, with recommendations for optimizing the size of these body tissue stores in early adulthood, and minimizing undesirable changes typically seen in middle and old age.

In vivo elemental partition analysis using fast neutrons. A tool for testing the efficacy of new clinical interventions

The nutritional status of patients can be evaluated by monitoring changes in body composition, including depletion of protein and muscle; distribution of adipose tissue; and changes in hydration status, and bone or cell mass. Fast neutron activation (for N and P) and neutron inelastic scattering (for C and O) are used to assess in vivo elements characteristic of specific body compartments. Nonbone phosphorus for muscle is measured by the 31P(n,alpha)28Al reaction, and nitrogen for protein via the (n,2n) fast neutron reaction. The carbon-to-oxygen (C/O) ratio is used to measure distribution of fat and lean tissue in the body and to monitor small changes in lean mass and its quality. In addition to evaluating the efficacy of new treatments, the method is used to study the mechanisms of depletion of lean tissue with aging.

Neutron activation analysis determination of body composition

The nutritional status of patients can be evaluated by monitoring changes in body composition, including the depletion of protein and muscle, adipose tissue distribution and changes in hydration status, bone or cell mass. Neutron activation analysis is a unique reference tool for the in-vivo determination of body composition. In this review we describe the recent changes in the field that followed the advent of new portable generators of fast neutrons, capable of performing elemental analysis in the clinical environment. New models were developed based on the partition of the measurable elements of the body. The recent developments help evaluate new treatments for wasting and obesity, in which change in body composition is the main outcome.

Hyperalimentation in autologous bone marrow transplantation for solid tumors. Comparison of total parenteral versus partial parenteral plus enteral nutrition

Recipients of autologous bone marrow transplantation (ABMT) for solid tumors need nutritional support to maintain their body weight (BW). Severe BW-reduction (9.9%) was noticed retrospectively in ten ABMT patients fed orally, despite intensive counseling or occasional tube feeding. A prospective, randomized study of hyperalimentation (25 g nitrogen (N) and 3400 nonprotein kilocalories) with total parenteral nutrition (TPN) or partial parenteral plus enteral nutrition by tube feeding (PPN/EN) was done in 22 patients. Nutritional assessment included balance measurements of N, Na, K, Cl, P, Ca, Mg, Cu, and Zn, and serial measurements of BW, serum albumin, prealbumin, and transferrin. Both regimens were effective in maintaining BW (maximum percent of change, 2.5) and N-balance. Blood products accounted for an additional N-intake of 13% in both groups. The TPN group had a higher dietary N-intake versus PPN/EN, a positive K balance but negative Ca, Mg, Cu, and Zn balances. More mineral supplementation was given in the PPN/EN group where positive K, Mg, and Zn balances were seen. Visceral proteins and IgG, IgA, and IgM levels were decreased on days 7, 14, and 21. Creatinine clearance increased significantly in both groups. Compared with TPN, the PPN/EN group showed a twofold number of patients with a positive blood culture, although this observation did not reach statistical significance and patients had fewer days of diarrhea (31.1% versus 54.3%, P less than 0.01). Hyperalimentation with PPN/EN is an acceptable alternative to TPN in the nutritional support of ABMT recipients.

Noninvasive techniques for measuring body elemental composition : State of the art and future prospects

In the past 20 yr, in vivo analysis of body elements by neutron activation has become an important tool in medical research. In particular, it provides a much needed means to make quantitative assessments of body composition of human beings in vivo. The data are useful both for basic physiological understanding and for diagnosis and management of a variety of diseases and disorders. This paper traces the development of the in vivo neutron activation technique from basic systems to the present state of the art facilities. A scan of some of the numerous clinical applications that have been made with this technique reveals the broad potentialities of in vivo neutron activation. The paper also considers alternative routes of future development and raises some of the questions now faced in making the technique more widely available to both medical practitioners and medical investigtors.In vivo neutron activation has opened a new era of both clinical diagnosis and therapy evaluation, and investigation into the modeling of body composition. The techniques are new, but it is already clear that considerable strides can be made in increasing accuracy and precision, increasing the number of elements susceptible to measurement, and reducing the dose required for the measurement.

Compartmental body composition based on total-body nitrogen, potassium, and calcium

The techniques of prompt gamma neutron-activation analysis for the measurement of total-body nitrogen and whole-body counting for the measurement of total-body potassium were used to determine the mass of muscle and nonmuscle lean tissue and their protein content in 135 normal male and female subjects, 20-80 yr of age. Age-related changes in the size of the muscle and nonmuscle compartments and their protein content provide basic data for the investigation of protein metabolism in aging subjects and in individuals with various metabolic disorders, particularly wasting diseases such as cancer. Significant age-related changes in the size of various body compartments were noted. The loss of muscle mass and its protein content contrasts with the relative constancy of the nonmuscle lean tissue and suggests that skeletal muscle is particularly vulnerable to the aging process.

Mammary carcinogenesis in Sprague--Dawley rats following 3 repeated exposures to 14.8 MeV neutrons and steroid receptor content of these tumor types

166 Sprague-Dawley Rats (148 males and 118 females) submitted to different hormonal conditions were exposed to 3 repeated whole-body irradiations of 14.8 MeV neutrons or sham-irradiated between 50 and 65 days of age (total absorbed doses: 3 x 2 rad and 3 x 8 rad). They were observed for 11 months. In the male group, a small number of tumors was obtained. In the female group, 75 breast neoplasms were scored in 41 of 78 irradiated animals (54 fibroadenomas, 20 adenocarcinomas and 1 fibrosarcoma). A second group of benign and malignant tumors was observed from 200 days on. The neoplastic response to fast neutron fractionated irradiations was increased by pregnancy with subsequent lactation. Estradiol and progesterone receptors were measured in 34 tumor samples. Fibroadenomas (1;5) and adenocarcinomas (1;3) bound labelled steroids. Like in human breast cancer metastases, steroid receptors are found in recurrences only if present in the primary tumor.

Total body sodium and chlorine in normal adults

Absolute levels of total body sodium (TBNa) and total body chlorine (TBCl) were determined in 81 normal adults (39 males, 42 females) by means of total body neutron activation analysis (TBNAA). The ages of the subjects ranged from 30 to 90 yr. The mean values for both TBNa and TBCl remained relatively constant throughout the age span studied for males, but decreased slightly for females over 60 yr of age. In order for the absolute measurements of Na and Cl to be of clinical value, the values must be compared to a predicted value based on the sex and body habitus of the individual. Normalization of TBNa values relative to body dimensions (weight, height, body surface area) were evaluated. In addition, TBNa was related to total body calcium (TBCa), which reflects skeletal mass, and TBK, which reflects muscle, or lean body mass. Normalization in terms of a linear combination of the TBCa and TBK was found to be the most satisfactory of all those studied. Sodium excess, NaES, defined as the amount of body sodium (mEq) in excess of body chlorine (mEq) was determined. Sodium excess correlated well with total body calcium. Values for total body sodium and chlorine obtained in the present study were compared with values previously reported in the literature.