Comparison of Volume Measurements and Bioimpedance Spectroscopy Using A Stand-on Device for Assessment of Unilateral Breast Cancer-Related Lymphedema.

Objective: Breast cancer related lymphedema (BCRL) may be assessed through objective measurement of limb swelling with common techniques including volumetric measurement using a tape measure or perometry, and measurement of extracellular water using bioimpedance spectroscopy (BIS). This study aimed to evaluate the performance of a stand-on BIS device for detection of BCRL, introduce a novel graphical method to compare volumetric and BIS methods alongside traditional specificity and sensitivity analysis, and determine and compare BIS thresholds with those published previously. Materials and Methods: Female participants with indocyanine green lymphography confirmed unilateral arm lymphedema (n = 197) and healthy controls (n = 267) were assessed using a cross-sectional study design. BIS and volumetric measures were obtained in a single session. Results: The BIS lymphedema index (L-Dex) method had a significantly higher sensitivity than the excess volume approach (area under the curve = 0.832 vs. 0.649, p = 0.0001). A threshold of L-Dex 6.5 had a higher true positive rate (70.6%) than L-Dex 10 (68.5%) although false positive rate increased from 0.4% to 2.6%. A threshold of 5% excess volume improved the true positive rate (68.5%) compared with 10% excess volume (49.7%) however the false positive rate increased to an unacceptable 47%. The L-Dex ranges in this study were not significantly different from previously published ranges. Conclusion: BIS was superior for identifying BCRL compared with volume measurements, reaffirming the value of this technique. However, it is recommended that BIS be used in conjunction with comprehensive evaluation of symptoms and clinical presentation. The proposed graphical method provides a simple and easily interpretable approach to compare and define concordance between the two commonly used methods for BCRL assessment namely limb volume and BIS L-Dex indices. The existing BIS (L-Dex) thresholds for presence of BCRL were also validated.

Determination of resistance at zero and infinite frequencies in bioimpedance spectroscopy for assessment of body composition in babies.

Objective. Bioimpedance spectroscopy (BIS) is a popular technique for the assessment of body composition in children and adults but has not found extensive use in babies and infants. This due primarily to technical difficulties of measurement in these groups. Although improvements in data modelling have, in part, mitigated this issue, the problem continues to yield unacceptably high rates of poor quality data. This study investigated an alternative data modelling procedure obviating issues associated with BIS measurements in babies and infants.Approach.BIS data are conventionally analysed according to the Cole model describing the impedance response of body tissues to an appliedACcurrent. This approach is susceptible to errors due to capacitive leakage errors of measurement at high frequency. The alternative is to model BIS data based on the resistance-frequency spectrum rather than the reactance-resistance Cole model thereby avoiding capacitive error impacts upon reactance measurements.Main results.The resistance-frequency approach allowed analysis of 100% of data files obtained from BIS measurements in 72 babies compared to 87% successful analyses with the Cole model. Resistance-frequency modelling error (percentage standard error of the estimate) was half that of the Cole method. Estimated resistances at zero and infinite frequency were used to predict body composition. Resistance-based prediction of fat-free mass (FFM) exhibited a 30% improvement in the two-standard deviation limits of agreement with reference FFM measured by air displacement plethysmography when compared to Cole model-based predictions.Significance.This study has demonstrated improvement in the analysis of BIS data based on the resistance frequency response rather than conventional Cole modelling. This approach is recommended for use where BIS data are compromised by high frequency capacitive leakage errors such as those obtained in babies and infants.

Development and validation of age-specific predictive equations for total energy expenditure and physical activity levels for older adults.

BACKGROUND: Predicting energy requirements for older adults is compromised by the underpinning data being extrapolated from younger adults. OBJECTIVES: To generate and validate new total energy expenditure (TEE) predictive equations specifically for older adults using readily available measures (age, weight, height) and to generate and test new physical activity level (PAL) values derived from 1) reference method of indirect calorimetry and 2) predictive equations in adults aged ≥65 y. METHODS: TEE derived from "gold standard" methods from n = 1657 (n = 1019 females, age range 65-90 y), was used to generate PAL values. PAL ranged 1.28-2.05 for males and 1.26-2.06 for females. Physical activity (PA) coefficients were also estimated and categorized (inactive to very active) from population means. Nonlinear regression was used to develop prediction equations for estimating TEE. Double cross-validation in a randomized, sex-stratified, age-matched 50:50 split, and leave one out cross-validation were performed. Comparisons were made with existing equations. RESULTS: Equations predicting TEE using the Institute of Medicine method are as follows: For males, TEE = -5680.17 - 17.50 × age (years) + PA coefficient × (6.96 × weight [kilograms] + 44.21 × height [centimeters]) + 1.13 × resting metabolic rate (RMR) (kilojoule/day). For females, TEE = -5290.72 - 8.38 × age (years) + PA coefficient × (9.77 × weight [kilograms] + 41.51 × height [centimeters]) + 1.05 × RMR (kilojoule/day), where PA coefficient values range from 1 (inactive) to 1.51 (highly active) in males and 1 to 1.44 in females respectively. Predictive performance for TEE from anthropometric variables and population mean PA was moderate with limits of agreement approximately ±30%. This improved to ±20% if PA was adjusted for activity category (inactive, low active, active, and very active). Where RMR was included as a predictor variable, the performance improved further to ±10% with a median absolute prediction error of approximately 4%. CONCLUSIONS: These new TEE prediction equations require only simple anthropometric data and are accurate and reproducible at a group level while performing better than existing equations. Substantial individual variability in PAL in older adults is the major source of variation when applied at an individual level.

A longitudinal analysis of resting energy expenditure and body composition in people with spinal cord injury undergoing surgical repair of pressure injuries: a pilot study.

BACKGROUND: Data informing energy needs of people with spinal cord injury (SCI) and pressure injuries are scarce, the impact of surgical repair unknown, and the role of body composition in healing unexplored. The study aims were to investigate resting energy expenditure (REE) over the course of pressure injury surgical repair, compare with available energy prediction equations, and explore associations between body composition and wound healing. METHODS: Indirect calorimetry measured REE pre-surgery, post-surgery, at suture removal and hospital discharge. A clinically significant change was defined as +/-10% difference from pre-surgery. Eight SCI-specific energy prediction equations were compared to pre-surgery REE. Wound breakdown (Yes/No), weight, waist circumference (WC), and body composition (fat mass [FM], fat-free mass [FFM], bioimpedance spectroscopy) were measured. RESULTS: Twenty people underwent pressure injury surgical repair (95% male, mean age 56 ± 12 years, 70% paraplegia). Between pre-surgery and discharge, mean REE increased (+118 kcal/d, p = 0.005), but with <10% change at any timepoint. An energy prediction equation incorporating FFM showed greatest agreement (rc = 0.779, 95% CI: 0.437, 0.924). Those with wound breakdown (65%) had a higher weight (12.7 kg, 95% CI: -4.0, 29.3), WC (17.8 cm, 95% CI: -5.1, 40.7), and FM % (36.0% [IQR 31.8, 40.2] vs 26.0% [IQR 15.6, 41.3]) than those without wound breakdown, although statistical significance was not reached. CONCLUSION: The presence of pressure injuries and subsequent surgical repair did not impact REE and energy prediction equations incorporating FFM performed best. While not statistically significant, clinically important differences in body composition were observed in those with wound breakdown.

Bioelectrical impedance analysis for assessment of body composition in infants and young children-A systematic literature review.

Bioelectrical impedance analysis (BIA) is an easy to use, portable tool, but the accuracy of the technique in infants and young children (<24 months) remains unclear. A systematic literature review was conducted to identify studies that have developed and validated BIA equations in this age group. MEDLINE, Scopus, EMBASE, and CENTRAL were searched for relevant literature published up until June 30, 2020, using terms related to bioelectrical impedance, body composition, and paediatrics. Two reviewers independently screened studies for eligibility, resulting in 15 studies that had developed and/or validated equations. Forty-six equations were developed and 34 validations were conducted. Most equations were developed in young infants (≤6 months), whereas only seven were developed among older infants and children (6-24 months). Most studies were identified as having a high risk of bias, and only a few included predominantly healthy children born at term. Using the best available evidence, BIA appears to predict body composition at least as well as other body composition tools; however, among younger infants BIA may provide little benefit over anthropometry-based prediction equations. Currently, none of the available equations can be recommended for use in research or in clinical practice.

Utility of specific bioelectrical impedance vector analysis for the assessment of body composition in children.

BACKGROUND & AIMS: Bioelectrical impedance analysis (BIA) is widely considered a body composition technique suitable for routine application. However, its utility in sick or malnourished children is complicated by variability in hydration. A BIA variant termed vector analysis (BIVA) aims to resolve this, by differentiating hydration from cell mass. However, the model was only partially supported by children's data. To improve accuracy, further adjustment for body shape variability has been proposed, known as specific BIVA (BIVAspecific). METHODS: We re-analysed body composition data from 281 children and adolescents (46% male) aged 4-20 years of European ancestry. Measurements included anthropometry, conventional BIA, BIVA outcomes adjusted either for height (BIVAconventional), or for height and body cross-sectional area (BIVAspecific), and fat-free mass (FFM) and fat mass (FM) by the criterion 4-component model. Graphic analysis and regression analysis were used to evaluate different BIA models for predicting FFM and FM. RESULTS: Age was strongly correlated with BIVAconventional parameters, but weakly with BIVAspecific parameters. FFM correlated more strongly with BIVAconventional than with BIVAspecific parameters, whereas the opposite pattern was found for FM. In multiple regression analyses, the best prediction models combined conventional BIA with BIVAspecific parameters, explaining 97.0% and 89.8% of the variance in FFM and FM respectively. These models could be further improved by incorporating body weight. CONCLUSIONS: The prediction of body composition can be improved by combining two different theoretical models, each of which appears to provide different information about the two components FFM and FM. Further work should test the utility of this approach in pediatric patients.

Three Decades of Bioelectrical Impedance Spectroscopy in Lymphedema Assessment: An Historical Perspective.

Bioelectrical impedance spectroscopy (BIS) is a technology that is widely used for the assessment of body composition. The method is based on the measurement of the electrical resistance of the body or a body region that can be quantitatively related to the amount of water in the tissues. Lymphedema is characterized, at least in its early stages, as an accumulation of lymph, an extracellular fluid. In the late 1980s, it was recognized that it might be possible to adapt BIS protocols to measure this increase in lymph volume. Subsequently, the use of BIS for the early detection of breast cancer-related lymphedema was demonstrated in the early 1990s, with BIS reference values indicative of lymphedema published in 2001. The subsequent two decades have seen BIS become a widely accepted method for lymphedema assessment. This review traces the evolution of the BIS technique since its inception and presents the current state of the art, with particular emphasis on utility in clinical practice.

Body Positional Effects on Bioimpedance Spectroscopy Measurements for Lymphedema Assessment of the Arm.

Background: Bioimpedance spectroscopy (BIS) measurements have conventionally been performed using a device that uses gel-backed electrodes with the patient in a supine position. More recently, impedance devices that use stainless steel electrodes with the patient in a standing position have become available. The aim of this study was to assess and compare BIS measurements made in three different body positions using two different impedance devices (lead device and stand-on device) in women with and without arm lymphedema. Methods: A cross-sectional study design was used to recruit two cohorts of women, healthy controls (n = 47) and those who had been diagnosed with breast cancer (n = 53) and were either at risk of (n = 14) or with unilateral arm lymphedema (n = 39). BIS measurements were taken three times in each position for each device. Results: Impedance measurements were reliably made using either a lead or stand-on device with a coefficient of variation being 0.6% or lower. Absolute impedance measurements for the stand-on device were larger than the comparable lead device values due to the difference in electrode position, but were highly correlated (r = 0.92, p < 0.0001). Interarm impedance ratios and L-Dex scores were slightly (3.1% equivalence), but significantly different. Conclusion: The findings support impedance measurements being made reliably using either the lead or stand-on device, representing supine and upright measurement positions, respectively. Data between devices were, however, not directly interchangeable.

An evaluation of phase angle, bioelectrical impedance vector analysis and impedance ratio for the assessment of disease status in children with nephrotic syndrome.

BACKGROUND: Oedema, characterized by accumulation of extracellular water (ECW), is one of the major clinical manifestations in children suffering from nephrotic syndrome (NS). The lack of a simple, inexpensive and harmless method for assessing ECW may be solved by the use of the bioelectrical impedance analysis (BIA) technique. The aims of this study were to examine whether phase angle (PA), bioelectrical impedance vector analysis (BIVA) and the impedance ratio (IR) reflect change in disease status in children with NS. METHODS: Eight children (age range: 2-10 years) with active NS (ANS group) were enrolled. In five of these (ANS* subgroup), impedance was also measured at remission (NSR group). Thirty-eight healthy children (age range: 2-10 years) were included as healthy controls (HC group). Whole-body impedance was measured with a bioimpedance spectroscopy device (Xitron 4200) with surface electrodes placed on the wrist and ankle. RESULTS: Values of PA, BIVA and IR were found to be significantly lower (p-value range < 0.001 to < 0.01) in the ANS patients compared to the HC and NSR groups. No significant differences were observed between the NSR and HC groups. CONCLUSION: The studied parameters can be used to assess change in disease status in NS patients. Data were consistent with NS being associated with expansion of ECW.

Comparison of estimated energy requirements using predictive equations with total energy expenditure measured by the doubly labelled water method in acute spinal cord injury.

STUDY DESIGN: Prospective, observational OBJECTIVES: To evaluate agreement between a reference method (doubly labelled water, DLW) of total energy expenditure (TEE) and published equations for estimating energy requirements in acute spinal cord injury (SCI). SETTING: Victoria, Australia METHODS: Twenty participants (18 male) within 8 weeks of traumatic SCI completed DLW, anthropometric and dietary intake assessments. Energy requirements were predicted using Harris-Benedict, Schofield, Henry, Nelson, Buchholz and Chun equations, multiplied by a combined activity and stress factor of 1.3, and the ratio method (kJ/kg body weight). Fat-free mass (FFM) and fat mass (FM) were calculated from TBW-derived DLW and from bioelectrical impedance spectroscopy (BIS). RESULTS: Median time since injury was 41 days. Median TEE was 9.1 MJ. Fair agreement was found between TEE and predicted energy requirements for the Chun (rc = 0.39), the Harris-Benedict equation (rc = 0.30), the ratio method (rc = 0.23) and the Buchholz (rc = 0.31) and Nelson equations (rc = 0.35), which incorporate measures of FFM and/or FM. Other equations showed weak concordance with DLW. When two hypermetabolic patients were removed, agreement between TEE and predicted energy requirements using the Buchholz equation increased to substantial (rc = 0.72) and using the Nelson (rc = 0.53) and Chun equations (rc = 0.53) increased to moderate. The Buchholz equation had the smallest limits of agreement (-2.4-2.3 MJ/d). CONCLUSION: The population-specific Buchholz equation that incorporates FFM, predicted from either BIS or DLW, demonstrated the best agreement in patients with acute SCI. SPONSORSHIP: The study was funded by grants from the Institute for Safety, Compensation and Recovery Research (ISCRR Project # NGE-E-13-078) and Austin Medical Research Foundation. M Panisset was supported by an Australian Postgraduate Award.

Electrode Equivalence for Use in Bioimpedance Spectroscopy Assessment of Lymphedema.

BACKGROUND: Bioimpedance spectroscopy (BIS) is commonly used in the assessment and monitoring of lymphedema. This study investigated electrodes as a source of variability that could impact the accuracy of BIS in the clinic and determined if Ag/AgCl electrocardiograph (ECG) electrodes could be used as an alternative to instrument-specific electrodes. METHODS AND RESULTS: Two types of Ag/AgCl electrodes were studied: instrument-specific bioimpedance electrodes (bioimpedance) and single tab ECG electrodes (cardiac). Six areas of investigation were addressed: intrinsic electrode resistance; electrode age; drive electrode position; electrode width/surface area; concordance between cardiac and bioimpedance electrodes; and mixing electrode types and batches. Participants included women (n = 26) and men (n = 8), both with (n = 4) and without lymphedema (n = 30). Resistance (R0) of the limbs was measured and used to calculate interlimb BIS ratios. Intrinsic electrode resistance varied between batches (p ≤ 0.001), with cardiac electrodes recording higher resistance. Electrode age had no impact on limb resistance (p = 0.85). Drive electrode position biased limb resistance (0.1%-2.3%) and electrode size/surface area had a small (≤1%), but significant effect on limb resistance (p ≤ 0.001). However, calculation of interlimb BIS ratios negated the impact of these as well as any effect of mixing electrode batches and types (p = 0.15-0.96). Electrode type had no impact on arm and leg resistance, or interlimb BIS ratios (p = 0.173-0.289). CONCLUSION: Calculation of interlimb BIS ratios improves accuracy of clinical BIS. Ag/AgCl cardiac electrodes can be used as an alternative to device-specific electrodes to measure limb resistance.

Bioelectrical impedance analysis for body composition assessment: reflections on accuracy, clinical utility, and standardisation.

Bioelectrical impedance analysis is an extremely popular method for assessment of body composition. Despite its wide-spread use over the past thirty years, its accuracy and clinical value is still questioned. Most frequently, criticisms focus on its purported poor absolute accuracy and that different impedance analysers or prediction equations fail to measure body composition identically. This perspective review highlights that the magnitude of errors associated with impedance methods are not dissimilar to those observed for so-called gold standard methods. It is argued that the focus on statistically significant but small differences between methods can obscure operational equivalence and that such differences may be of minor clinical significance. Finally, the need for better standardization of protocols and the need for consensus on what is a minimal clinically important difference between methods is highlighted.

Human Milk Adiponectin and Leptin and Infant Body Composition over the First 12 Months of Lactation.

Human milk (HM) adipokines may influence infant feeding patterns, appetite regulation, and body composition (BC). The associations between concentrations/calculated daily intakes (CDI) of HM adipokines in the first 12 months postpartum and maternal/term infant BC, and infant breastfeeding parameters were investigated. BC of breastfeeding dyads (n = 20) was measured at 2, 5, 9, and/or 12 months postpartum with ultrasound skinfolds (infants) and bioimpedance spectroscopy (infants/mothers). 24-h milk intake and feeding frequency were measured along with whole milk adiponectin and skim and whole milk leptin (SML and WML) and CDI were calculated. Statistical analysis used linear regression/mixed effects models; results were adjusted for multiple comparisons. Adipokine concentrations did not associate with infant BC. Higher CDI of adiponectin were associated with lower infant fat-free mass (FFM; p = 0.005) and FFM index (FFMI; p = 0.009) and higher fat mass (FM; p < 0.001), FM index (FMI; p < 0.001), and %FM (p < 0.001). Higher CDI of SML were associated with higher infant FM (p < 0.001), FMI (p < 0.001), and %FM (p = 0.002). At 12 months, higher CDI of WML were associated with larger increases in infant adiposity (2⁻12 month: FM, p = 0.0006; %FM, p = 0.0004); higher CDI of SML were associated with a larger decrease in FFMI (5⁻12 months: p = 0.0004). Intakes of HM adipokines differentially influence development of infant BC in the first year of life, which is a critical window of infant programming and may potentially influence risk of later disease via modulation of BC.

Assessment of limb edema in pediatric post-thrombotic syndrome.

BACKGROUND: Pediatric tools for diagnosis of post-thrombotic syndrome (PTS) include the assessment of limb edema as a symptom (patient/proxy-reported) and as a sign. However, it is unclear whether these two approaches refer to the same clinical aspect of PTS. This could result in overestimation of disease severity. We sought to evaluate the correlation among different techniques to assess limb edema as a sign and as a symptom in children who sustained upper extremity (UE) or lower extremity (LE) deep vein thrombosis (DVT) and were, therefore, at risk of PTS. METHODS: Limb edema was cross-sectionally measured as a symptom (ie, patient- or proxy-reported) and as a sign (ie, clinician-assessed limb circumference difference, limb volume ratio, bioimpedance spectroscopy ratio (BIS), and durometry ratio) in 140 children at risk of PTS (n = 70 UE-DVT, n = 70 LE-DVT). Item-item correlations were estimated using Pearson or Spearman correlation coefficients, as appropriate, and separately for the UE and LE groups. RESULTS: In the UE-DVT group, proxy-reported swelling correlated weakly to moderately with circumference difference and with volume ratio, but not with BIS ratio. In the LE-DVT group, proxy-reported swelling correlated moderately with thigh circumference difference and volume ratio, and patient-reported swelling correlated moderately with BIS ratio. CONCLUSION: Our findings suggest that patient/proxy-reported and clinician-assessed limb edema measure slightly different aspects of PTS, justifying their inclusion in pediatric PTS tools. In addition, proxy-reported swelling was in closer agreement with clinician-assessed total limb size (ie, observed edema), and patient-reported swelling in the LE seemed to reflect limb fluid content (ie, perceived edema).

Inter-Changeability of Impedance Devices for Lymphedema Assessment.

Impedance technology is a popular technique for the early detection of lymphedema. The preferred approach is to use bioimpedance spectroscopy (BIS), with measurements being made with the subject lying supine, although attempts have been made to use single or multiple frequency impedance measurements obtained while the subject is standing. The aim of the present study was to determine the equivalence of these different approaches. Impedance measurements of the individual limbs of 37 healthy individuals were determined using both a stand-on, multi-frequency impedance device and a supine impedance spectroscopy instrument. Significant differences were found between the instruments in both absolute impedance values and, importantly, inter-limb impedance ratios. Since impedance ratios in healthy individuals provide the reference standard for detection of lymphedema, these data indicate that the methods are not interchangeable. Consideration of the errors associated with each method indicates that the BIS remains the preferred method for lymphedema detection.

Assessment of breast cancer-related lymphedema: a comparison of moisture meter and spot bioimpedance measurement.

BACKGROUND: Tissue dielectric constant (TDC) and spot bioimpedance measurement (BIA) have a role in the assessment of tissue composition changes in breast cancer-related lymphedema (BCRL). Our aims were to determine whether TDC and spot BIA measures could detect inter-limb differences in BCRL, explore the relationship between methods, and establish the intra-rater reliability and technical error of measurement for TDC. METHODS AND RESULTS: Women with (n=20) and without (n=4) unilateral BCRL participated. Circumference, TDC, and spot BIA measures were completed on the most affected region of the arm for BCRL participants and at a standardized forearm point in women without lymphedema. All measures were compared to measurements from an identical location on the contralateral arm. The affected arm differed significantly to the unaffected arm of women with BCRL for TDC and spot BIA measures. The median (IQR) differences were: extra-small probe 5.75 (3.10-8.21), small probe 3.50 (1.16-6.89), medium probe 5.08 (0.88-10.91), and for spot BIA measurement (-35.20 Ω; -59.75 to -14.85 Ω). The small and medium TDC probe measures were moderately correlated to spot bioimpedance measurements (r=-0.54 and r=-0.43, respectively). Intra-rater reliability coefficients (ICC2,1) of TDC measures ranged from 0.50 (95% CI: 0.12-0.75) to 0.92 (0.82-0.96). TDC technical error of measurement for women with lymphedema varied from 10.5% to 13.3%. CONCLUSIONS: Both TDC and spot bioimpedance may have a role in clinical assessment of tissue compositional change in BCRL. Their relationship with tissue composition, assessed by imaging, is now required.

Assessment of segmental arm soft tissue composition in breast cancer-related lymphedema: a pilot study using dual energy X-ray absorptiometry and bioimpedance spectroscopy.

BACKGROUND: Changes in arm soft tissue composition, especially increased adipose tissue, has been found in advanced, non-pitting breast cancer-related lymphedema (BCRL). The aim of this study was to examine whether these changes were localized to any particular region of the arm and whether they occurred in lymphedema which still pitted to pressure. Secondary aims were to explore relationships between arm segment volumes, bioimpedance spectroscopy (BIS) measurements of extracellular fluid (ECF), and dual-energy X-ray absorptiometry (DXA) measurements of tissue composition. METHODS AND RESULTS: Nine women with unilateral BCRL participated. The dominant arm was affected in 4 women, and all presented with lymphedema that pitted to pressure. Arm volume was calculated from circumferences by the truncated cone method, ECF was determined with BIS and fat and lean tissue content measured by DXA. BIS and DXA measurements for women with lymphedema were made of the whole arm and also of four 10 cm-segments measured from the ulnar styloid at the wrist. Whole arm DXA data were compared to those of 45 women of similar age and body mass index without lymphedema. All women with lymphedema had a significantly larger absolute fat mass in their affected arm compared to their unaffected arm, (median difference between arms 146.9 g). The forearm segment 10 - 20 cm proximal to the wrist had the highest median inter-limb fat difference of all four arm segments. CONCLUSIONS: The soft tissue composition changes associated with BCRL may occur in the presence of pitting and predominantly affect the proximal forearm.

Study Protocol--accurate assessment of kidney function in Indigenous Australians: aims and methods of the eGFR study.

BACKGROUND: There is an overwhelming burden of cardiovascular disease, type 2 diabetes and chronic kidney disease among Indigenous Australians. In this high risk population, it is vital that we are able to measure accurately kidney function. Glomerular filtration rate is the best overall marker of kidney function. However, differences in body build and body composition between Indigenous and non-Indigenous Australians suggest that creatinine-based estimates of glomerular filtration rate derived for European populations may not be appropriate for Indigenous Australians. The burden of kidney disease is borne disproportionately by Indigenous Australians in central and northern Australia, and there is significant heterogeneity in body build and composition within and amongst these groups. This heterogeneity might differentially affect the accuracy of estimation of glomerular filtration rate between different Indigenous groups. By assessing kidney function in Indigenous Australians from Northern Queensland, Northern Territory and Western Australia, we aim to determine a validated and practical measure of glomerular filtration rate suitable for use in all Indigenous Australians. METHODS/DESIGN: A cross-sectional study of Indigenous Australian adults (target n = 600, 50% male) across 4 sites: Top End, Northern Territory; Central Australia; Far North Queensland and Western Australia. The reference measure of glomerular filtration rate was the plasma disappearance rate of iohexol over 4 hours. We will compare the accuracy of the following glomerular filtration rate measures with the reference measure: Modification of Diet in Renal Disease 4-variable formula, Chronic Kidney Disease Epidemiology Collaboration equation, Cockcroft-Gault formula and cystatin C- derived estimates. Detailed assessment of body build and composition was performed using anthropometric measurements, skinfold thicknesses, bioelectrical impedance and a sub-study used dual-energy X-ray absorptiometry. A questionnaire was performed for socio-economic status and medical history. DISCUSSION: We have successfully managed several operational challenges within this multi-centre complex clinical research project performed across remote North, Western and Central Australia. It seems unlikely that a single correction factor (similar to that for African-Americans) to the equation for estimated glomerular filtration rate will prove appropriate or practical for Indigenous Australians. However, it may be that a modification of the equation in Indigenous Australians would be to include a measure of fat-free mass.

Operational equivalence of bioimpedance indices and perometry for the assessment of unilateral arm lymphedema.

BACKGROUND: The aim was to assess the agreement between bioimpedance indices and inter-limb volume differences, as assessed by perometry, for assessment of unilateral arm lymphedema. METHODS: Impedance was measured in the arms of 45 women with lymphedema and a separate control group without lymphedema (n = 21). Arm volume was measured at the same time by perometry. The impedance indices, (ratio of impedances between limbs and the L-dex scores) were compared to the inter-limb volume differences using concordance correlation analysis. RESULTS: Impedance indices were highly correlated (r = 0.926) with the difference in arm volume measured by perometry. CONCLUSIONS: Bioelectrical impedance analysis, although not providing a quantitative volume measurement of lymphedema, provides a measurement index that is highly correlated with quantitative measurements of the volume increase in limb size seen in lymphedema. The speed and ease of the impedance technique renders it a suitable alternative to perometry for the assessment of lymphedema.