Are bioelectric impedance measurements valid in patients with cystic fibrosis?

Evidence on nutritional assessment techniques and parameters used to determine the nutritional status of children and adolescents: systematic review

This article aims to review systematically the evidence on nutritional assessment techniques and parameters used to determine the nutritional status of children and adolescents. The literature review and the selection of publications were performed using the Medline, Lilacs, SciELO, Embase, personal files. 17 studies were identified, 7 addressed the anthropometric indices as the main outcome, 7 analyzed the growth and development of children and adolescents through growth curves, and the remainder surveyed body composition. In general, all met the quality criteria, unless 6 of the articles who did not discuss the limitations. The literature review suggests several techniques and parameters that can be applied to determine the nutritional status of children and adolescents from different countries. Growth graphs are essential to assess the health of children, but depend greatly of the growth tables used. Although BMI can be practical, it does not distinguish body fat from lean mass. The best interpretation of anthropometry will depend of valid reference values for age range of the study population. BIA is a quick feasible method, but the measurement has some various nationalities.

Nutritional assessment

Hospital-based malnutrition continues to be an important comorbidity affecting clinical outcomes. Knowledge of performing an appropriate nutrition assessment and implementing a rational nutrition therapy should be part of any patient's hospital plan of care. Familiarity with nutrition assessment scoring systems and nutrition assessment tools should be part of any gastroenterologist's expertise. Assessment of a patient's caloric and protein needs should be part of any hospital patient's clinical evaluation.

Body composition assessment in adults with cystic fibrosis: comparison of dual-energy X-ray absorptiometry with skinfolds and bioelectrical impedance analysis

OBJECTIVE

We compared body composition measurement in adults with cystic fibrosis (CF) by using non-invasive methods (skinfold thicknesses and bioelectrical impedance analysis [BIA]) with dual-energy X-ray absorptiometry (DXA).

METHODS

Seventy-six adults with CF (mean age 29.9 +/- 7.9 y, mean body mass index 21.5 +/- 2.5 kg/m(2)) were studied. Body composition was measured to calculate fat-free mass (FFM) using DXA, the sum of four skinfold thicknesses, and BIA (predictive equations of Lukaski and of Segal).

RESULTS

Mean FFM values +/- standard deviation measured using DXA were 54.8 +/- 7.3 kg in men and 41.2 +/- 3.9 kg in women. Mean FFM values measured using BIA/Lukaski were 51.5 +/- 7.8 kg in men and 40.4 +/- 4.9 kg in women (P < 0.0005 for men, not significant for women for comparison with DXA). Mean FFM values measured using BIA/Segal were 54.2 +/- 7.5 kg for men and 44.1 +/- 5.9 kg for women (not significant for men, P < 0.0005 for women for comparison with DXA). Mean FFM values measured using skinfolds were significantly higher than those for FFM with DXA (57.2 +/- 7.2 kg in men, 43.3 +/- 4.3 kg in women, P < 0.0005 for comparison with DXA). The 95% limits of agreement with FFM using DXA were, for men and women, respectively, -8.3 to 1.7 kg and -6.4 to 4.8 kg for BIA/Lukaski, -4.8 to 3.6 kg and -3.1 to 8.9 kg for BIA/Segal, and -2.8 to 7.3 kg and -1.5 to 5.7 kg for skinfolds.

CONCLUSION

This study suggests that skinfold thickness measurements and BIA will incorrectly estimate FFM in many adults with CF compared with DXA measurements of FFM. These methods have limited application in the assessment of body composition in individual adult patients with CF.

Long-term trial of cyproheptadine as an appetite stimulant in cystic fibrosis

Appetite stimulants have been used to help overcome decreased appetite and malnutrition in children and adults with various chronic illnesses, including cystic fibrosis (CF). Stimulants have included megestrol acetate (MA), cyproheptadine hydrochloride (CH), cannabinoids, hydrazine sulfate, anabolic hormones, and growth hormone. Many of these, including MA, have substantial side effects and may not be suitable for prolonged use. We previously studied the effects of CH on weight gain in a short-term (12 week) trial in CF with good results compared to placebo. Side effects were few, and weight gain was significant. In this study, we sought to determine the effects of CH over a longer term in order to assess its suitability for prolonged use. Sixteen CF children and adults enrolled in the original short-term study subsequently entered this study, and 12 completed the 9-month trial. All patients receiving placebo in the original short-term study received CH 4 mg up to four times a day in the long-term study continuation, and those receiving CH in the short-term study continued on the drug. No pill counts were done, and patients were queried at quarterly visits as to their CH use. Anthropometrics and spirometry were also done quarterly, and antibiotic use was quantified. Subjects who had changed from placebo (CH2 group) gained weight significantly over 3-6 months, and those continuing on CH (CH1 group) generally maintained previously gained weight over the duration of the study. Select spirometric measures improved in both groups but not significantly, and side effects were mild. CH appears to be an effective appetite stimulant in CF, and generally maintains its effect over time with an acceptable side-effect profile.

Assessment of nutritional status in adult patients with cystic fibrosis: Whole-body bioimpedance vs body mass index, skinfolds, and leg-to-leg bioimpedance

OBJECTIVE

To investigate whether body mass index (BMI) or body fat percentage estimated from BMI, skinfolds, or leg-to-leg bioimpedance are good indicators of nutritional status in adult patients with cystic fibrosis. Body fat percentage measured by whole-body bioimpedance was used as the reference method.

DESIGN

Cross-sectional study using four methods to estimate body fat percentage. All patients filled out a food frequency and a physical activity questionnaire for assessment of their habitual food intake and energy requirements, respectively.

SUBJECTS/SETTING

Thirty-five adult patients (23 men/12 women) with cystic fibrosis, age range 18 to 46 years, were measured during their yearly visit at the outpatient clinic of the Cystic Fibrosis Center in Utrecht, the Netherlands.

STATISTICAL ANALYSIS

Mean+/-standard deviation was calculated for all measurements and 95% confidence intervals for differences between methods. Bland-Altman plots were used to assess differences between the measures of body composition and Pearson correlation coefficients were calculated to determine the relationships between them, and between the energy requirements and the energy intakes.

RESULTS

For men the whole-body body fat percentage reference was 14.1%+/-3.0, body fat percentage estimated from BMI was 15.8%+/-4.3, body fat percentage estimated from skinfolds was 8.6%+/-4.8, and body fat percentage estimated from leg-to-leg bioimpedance was 13.1%+/-4.9. For women the whole-body body fat percentage reference was 24.0%+/-5.9, body fat percentage estimated from BMI was 25.1%+/-4.0, body fat percentage estimated from skinfolds was 17.0%+/-4.8, and body fat percentage estimated from leg-to-leg bioimpedance was 25.0%+/-6.9. Body fat percentage estimated from BMI and body fat percentage estimated from skinfolds were significantly different from the reference value for body fat percentage (P <.05). The correlation coefficients between the reference body fat percentage and body fat percentage estimated from BMI, from skinfolds, and from leg-to-leg bioimpedance were all more than 0.72. In all but one patient, nutritional status was correctly assessed by BMI: those with a BMI less than 18.5 had body fat percentage less than 10% (men) or less than 20% (women). The mean energy intake of the men was 141% of the Recommended Dietary Allowance as proposed in European and Dutch guidelines. The mean energy intake of the women was 94% of the Recommended Dietary Allowance.

CONCLUSIONS

A simple calculation of BMI is adequate to diagnose nutritional status in adult patients with cystic fibrosis. Bioimpedance measurements are only needed when nutritional therapy specifically focuses on lean body mass.

Assessment of nutritional status in children with cystic fibrosis: conventional anthropometry and bioelectrical impedance analysis. A cross-sectional study in Dutch patients

BACKGROUND

Assessment of nutritional status in children with cystic fibrosis (CF) is clinically relevant. Methods to measure nutritional status should be reliable and non-invasive, and reference values should be available.

AIM

To compare weight and height measurements and measurements of specific body compartments in children with CF.

METHODS

In a cross-sectional survey of 58 children with CF (28 females), we compared height and weight (expressed as: weight-for-height, body mass index (BMI), height-for-age and weight-for-age) with fat mass (skinfold sum (SFS)), muscle mass (upper arm circumference (UAC)) and bioelectrical impedance analysis (BIA). Results were expressed as Z-scores, using Dutch reference values.

RESULTS

BMI and weight-for-height were within the normal range (mean Z-score (range): -0.13 (-1.5, 2.7) and -0.02 (-1.7, 2.8)). Weight and height corrected for age were below normal (mean Z-score (range): -0.79 (-2.4, -0.05) and -1.2 (-2.8, 1.4) (P<0.01)). Lean body mass by skinfold sum (LBM(sfs)), UAC and BIA were also significantly below reference values (mean Z-score (range): -0.9 (-2.2, 1.8), -0.95 (-2.4, 1.8) and -1.1 (-3.6, 1.0) (P<0.01)). Lean body mass (LBM) by BIA correlated with LBM(sfs). BIA systematically underestimated LBM in both CF patients and in control subjects.

CONCLUSION

Nutritional status of children with CF must be evaluated, using age-corrected weight and height expressed in Z-score. LBM estimated by SFS, UAC and by BIA appear to be useful, although longitudinal studies in CF children should be performed to evaluate their clinical significance in detecting changes in nutritional status.

Total body water in children with cystic fibrosis using bioelectrical impedance

BACKGROUND

The aim of this study was to assess the ability of commercially available single frequency bioelectrical impedance analysis (BIA) to predict total body water and hence body composition in a cohort of children with cystic fibrosis (CF).

METHODS

In 56 (31 girls, 25 boys) children aged 4 to 18 years, total body water was predicted using BIA and measured using a deuterium oxide dilution technique. Each child provided a urine sample before consuming 0.5 g/kg body weight 10% deuterium oxide. A further urine sample was collected between 4 and 6 h later.

RESULTS

There was a mean bias between predicted and measured total body water of 1.1 L. The bias was consistent across the range of total body water measured in this study. The relationship between height2/impedance and measured total body water was TBW=0.35+0.74*height2/impedance. This equation is similar to other equations found in healthy children.

CONCLUSION

We have shown that a commercially available bioelectrical device underestimates measured total body water. We have generated a prediction equation for the population studied, which we believe might enhance the accuracy of the method in children with cystic fibrosis.

Cyproheptadine is an effective appetite stimulant in cystic fibrosis

Chronic pulmonary infection and intestinal malabsorption often lead to malnutrition in children and adults with cystic fibrosis (CF). Appetite stimulants, along with provision of adequate calories, may aid in overcoming nutritional deficits, allowing a better prognosis. We undertook a trial of cyproheptadine hydrochloride (CH) to determine its effectiveness as an appetite stimulant in 18 adults and children with CF. This was a 12-week, randomized, double-blind, controlled trial of CH vs. placebo. Eighteen subjects with documented CF (sweat or genetics positive), minimum age of 5 years, and ideal body weight for height <100% were entered, and 16 completed the study. Subjects were seen at baseline and every 4 weeks. Measures included baseline demographics, Shwachman score, anthropometrics (weight, height, body mass index, skin folds, and body composition by bioelectric impedance analysis), spirometry, caloric intake, days of oral (PO) and intravenous (IV) antibiotics, and a symptom and satisfaction survey. Subjects in the CH group showed significant increases in weight (mean 3.45 kg vs. 1.1 kg in the placebo group), height, BMI percentiles, ideal body weight/height, weight for age z-scores, and fat and fat-free mass. There were no changes or differences in PO or IV antibiotic use or spirometric changes. No significant side effects except transient mild sedation occurred in the CH group. Patient acceptance was good. In conclusion, CH appears to be an effective appetite stimulant with minimal side effects in children and adults with CF.

Anaerobic exercise in pediatric cystic fibrosis

Anaerobic fitness is important for daily functioning of children with cystic fibrosis (CF). The aim of this study was to assess the determinants of anaerobic performance in CF. Anaerobic performance was measured in 39 children with CF (mean age, 13.2 +/- 1.8 (SD) years, forced expired volume in 1 sec (FEV(1)) 81.6 +/- 22.1% predicted), using a Wingate anaerobic test. Significant associations were found for peak power (PP) and mean power (MP) with fat-free mass (FFM) body weight, body mass index, maximal isometric muscle force, and aerobic capacity. Pulmonary function was correlated with anaerobic indices when controlled for FFM. Multiple regression analysis indicated that FFM and FEV(1) accounted for 82% and 86% of the variability in PP and MP, respectively. Patients with moderate CF (FEV(1) < 80%), as compared to mild CF (FEV(1) >/= 80%), had higher PP (difference = 85 W, 95% CI = 27-144 W) and MP (difference = 53 W, 95% CI = 42-63 W) at equivalent FFM. Our results indicate that FFM and pulmonary function are important determinants of anaerobic exercise performance in children with CF. With progression of pulmonary disease, anaerobic performance may be enhanced.

Normal volume of distribution of tobramycin in a mother and daughter with a CFTR splice mutation (1717 - 1G --> A)

A mother and daughter pair with CF who shared a splice mutation (1717 - 1G --> A) had a normal volume of distribution of tobramycin. The literature on tobramycin pharmacokinetics, which was published before the genetic defect was identified, is discussed. The authors speculate on the role of CFTR in the distribution of aminoglycosides and recommend that CFTR mutations should be clarified in all future studies of tobramycin pharmacokinetics in patients with CF.

The prediction of body composition in Chinese Australian females

OBJECTIVE

To determine the efficacy of applying specific body composition techniques to, and assess the relationship between body mass index (BMI) and body fat levels for Chinese Australian females.

DESIGN

Statistical comparative analysis of body composition techniques.

SUBJECTS

Australian resident females of Chinese extraction (n=40) (aged 18-45 y, mean 32.5+/-8.0; BMI range 15.7-30.9 kg/m2, mean 21.7+/-3.1 kg/m2, median 20.8 kg/m2).

MEASUREMENTS

Body composition determined using bio-electrical impedance analysis (BIA), the skin-fold equations of Durnin and Womersley (D&W) and a deuterium dilution technique. Body size was calculated as the body mass index (BMI) weight/height(2) (kg/m2).

RESULTS

With a median BMI of 20.8, range 15.7-30.9, an acceptable BMI existed for 87.5% of the subjects (mean (s.d.) 21.7+/-3.1 kg/m2). Percentage fat mass (%FM) from the deuterium dilution technique (mean (s.d.) 35.6+/-6.4) suggested 75% were overweight or obese. %FM from the D&W equation (mean (s.d.) 28.0+/-3.9) and BIA (mean (s.d.) 29.4+/-5.1) also indicated a tendency towards overweight or obese. The deuterium technique was significantly correlated and significantly different to the D&W eqn, r=0.71 P=0.001; and BIA, r=0.77, P=0.001. Bland and Altman analysis indicated that bias existed between the techniques (BIA mean (s.d.)-6.7+/-4.1) and D&W equation mean (s.d.)-6+/-4.5) when compared to the deuterium method.

CONCLUSIONS

Despite a low mean BMI, body fat levels determined by the three methods suggested that, overall, an unsatisfactory body composition existed. The levels of overweight and obesity (%FM>30) were higher than reported in previous research despite a mean BMI lower than the Australian national average. Comparative analysis suggested that the body fat prediction techniques used may be precise but not accurate. Comparative results obtained for the BIA and D&W equation techniques suggest an overestimation of body fat levels for leaner individuals and under estimation for overfat individuals. The results support the notion that accurate determination of body composition and the determination of appropriate body size may require equations developed for specific ethnic populations.

Problems of nutritional assessment in the acute setting

Surveys have shown that 20-50% of hospital admissions suffer from nutritional depletion and that there is failure to recognize its existence and significance. More emphasis must be placed in clinical medicine on identifying subjects who are at high risk of developing disease-related malnutrition. There is a need to screen patients on admission to hospital to identify those at risk of nutrition-related complications. More formal determination of nutritional status should be carried out to define the nutritional status of the patient and to monitor changes in nutritional status during nutritional support. The most frequently used tests of nutritional status include dietary, anthropometric, biochemical and functional indices of nutritional status. It is important, and indeed is the skill of the nutritional care team (particularly the dietitian) to be able to evaluate these measurements, as many of them are affected by non-nutritional factors. There is no consensus on the best method for the accurate assessment of nutritional status. Practical difficulties arise with individual measurements and in their interpretation in the acute setting. The aim of the present paper is to identify the most relevant variables to measure in clinical medicine, and to discuss the limitations of their use in the acute setting.

Nutritional impact of antipseudomonas intravenous antibiotic courses in cystic fibrosis

OBJECTIVE

To evaluate the short term effects on nutritional status of home intravenous anti-pseudomonas antibiotic courses in cystic fibrosis (CF) patients chronically colonised with Pseudomonas aeruginosa.

DESIGN

A prospective study involving 38 CF patients, mean age 10.9 (SD 4.3) years (range 4.3 to 22.2 years), presenting with pulmonary exacerbations of P aeruginosa infection. The patients received a 14 day antibiotic course of intravenous ceftazidime (200 mg/kg/day) and either amikacin (35 mg/kg/day) or tobramycin (15 mg/kg/day). Nutritional evaluation on days 1 and 14 involved measurements of weight, weight/height ratio (per cent of predicted value), energy intake (per cent of recommended daily allowances), serum prealbumin, and body composition assessed by two methods: bioelectrical analysis (BIA) and skinfold anthropometry. The non-parametric Wilcoxon t test was used for statistical analysis, with a Bland-Altman plot to assess the degree of agreement between the two methods of evaluating body composition.

RESULTS

Weight increased by 1.0 (0.8) kg (p < 0.001); weight/height increased from 94.4(12.2)% to 98(12.7)% (p < 0.001), energy intake from 107(32)% to 119(41)% (p < 0.02), and prealbumin from 183 (63) to 276 (89) mg/l (p < 0.001). Fat mass increased by 0.8 (1.0) kg (p < 0.001), without any significant change in fat-free mass. The limits of agreement between BIA and anthropometry were -0.7 kg and +1.1 kg.

CONCLUSIONS

Antibiotic courses allow an improvement in nutritional status in CF patients, with a gain in fat mass.

Evaluation of bioelectrical impedance for prospective nutritional assessment in cystic fibrosis

We have compared the use of bioelectrical impedance analysis (BIA) with anthropometry for the prediction of changes in total body potassium (TBK) in a group (n = 31) of children with cystic fibrosis. Linear regression analysis showed that TBK was highly correlated (r > 0.93) with height2/impedance, weight, height, and fat-free mass (FFM) estimated from skin-fold measurements. Changes in TBK were also correlated, but less well, with changes in height2/impedance, weight, height, and FFM (r = 0.69, 0.59, 0.44, and 0.40, respectively). The children were divided into two groups: those who had normal accretion of TBK (> 5%/y) and those who had suboptimal accretion of TBK (< 5%/y). Analysis of variance showed that the significant difference in the change in TBK between the groups was detectable by concomitant changes in impedance and weight but not by changes in height, FFM, or weight and height Z scores. The results of this study suggest that serial BIA measures may be useful as a predictor of progressive undernutrition and poor growth in children with cystic fibrosis.

International Federation of Clinical Chemistry. Laboratory assessment of protein-energy status

Laboratory and non-laboratory methods for assessing protein-energy nutritional status are reviewed. These are classified into methods for assessing adequacy of recent nutritional intake, methods for assessing whole body status, and tests which assist in the interpretation of these assessments. Each measurement is critically discussed in terms of the rationale for its use, the method of analysis, reference values, technical interference and limitations of methods, the effects of nutritional status and of other factors on the results, its overall usefulness in nutritional assessment, and its value relative to other methods. Non-laboratory tests such as dietary assessment, indirect calorimetry, functional tests and the many methods available for assessment of body composition, including anthropometry, bioelectrical impedance and isotope and imaging techniques, are compared with the clinical chemistry tests in common use, such as nitrogen balance, plasma protein measurements and urinary markers of muscle metabolism. This review provides comprehensive and practical advice on the use and limitations of these tests in the assessment of protein-energy nutritional status of a group, or of an individual patient.