Bioelectrical impedance validation studies: alternative approaches to their interpretation

Ward, Leigh C.

doi:10.1038/ejcn.2012.159

Cited by 14 publications

(15 citation statements)

References 23 publications

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“…Validation studies in clinical populations have typically reported good mean‐level agreement between bioimpedance and reference methods based on correlation and paired t ‐test statistics, but poor accuracy at the individual level (ie, wide limits of agreement by Bland‐Altman analysis) raises doubts about the capacity of bioimpedance techniques to accurately quantify whole body compartments. Each reference method has a certain amount of inherent error, and it can be argued that the aforementioned statistical techniques used to prove validity do not effectively take into account the errors associated with the reference 20 . Furthermore, prediction equations are scaled to a particular reference method and can produce error when evaluated against a different reference method.…”

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confidence: 99%

Bioimpedance at the Bedside

et al. 2015

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The loss of muscle mass is a defining characteristic of malnutrition, and there is ongoing interest in the assessment of lean tissue at the bedside. Globally, bioimpedance techniques have been widely appreciated for their noninvasiveness, safety, ease of use, portability, and relatively low cost compared with other clinically available methods. In this brief update, we review the 3 primary types of commercially available bioimpedance devices (single- and multiple-frequency and spectroscopy) and differentiate the underlying theory and current applications of each. We also address limitations and potential opportunities for using these devices at the bedside for clinical assessment. Mixed reports in the validation literature for all bioimpedance approaches have raised questions about absolute accuracy to estimate whole body composition in clinical populations, particularly those with abnormal fluid status and/or body geometry in whom underlying method assumptions may be violated. Careful selection of equations can improve whole body estimates by single- and multiple-frequency techniques; however, not all devices will allow for this approach. Research is increasing on the use of bioimpedance variables including phase angle and impedance ratio as potential markers of nutrition status and/or clinical outcomes; consensus on reference cut-points for interpreting these markers has yet to be established. Novel developments in the bioimpedance spectroscopy approach are allowing for improved fluid management in individuals receiving dialysis; these developments have implications for the clinical management of other conditions associated with fluid overload and may also provide enhanced whole body estimates of lean tissue through new modeling procedures.

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confidence: 99%

Bioimpedance at the Bedside

et al. 2015

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“…Limitations associated with the bia technique for predicting body composition in patients with cancer include the assumption of constant hydration and ffm composition, which can be different in obesity, various diseases, various age groups, and various ethnic groups 21,22 . In our opinion, further research with a larger sample size could potentially support our results, providing an avenue for early nutrition intervention and corrective nutritive replacement, which, combined with oncology intervention, might ultimately lead to increased survival in this patient population.…”

Section: Discussionmentioning

confidence: 99%

Extracellular–to–Body Cell Mass Ratio and Subjective Global Assessment in Head-and-Neck Cancers

2014

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Background: The ratio of extracellular mass to body cell mass (ecm/bcm), determined by bioelectrical impedance analysis, has been found to be a potentially useful indicator of nutrition status. Subjective global assessment (sga) is a subjective method of evaluating nutrition status in head-and-neck cancer. The present study was conducted to investigate the association between ecm/bcm and sga in head-and-neck cancer. Methods: Patients were classified as either well-nourished or malnourished by sga. Bioelectrical impedance analysis was conducted on a population of 75 patients with histologically confirmed head-and-neck cancer, and the ecm/bcm was calculated. Receiver operating characteristic curves were estimated using the nonparametric method to determine an optimal cut-off value of the ecm/bcm. Results: Compared with malnourished patients, those who were well-nourished had a statistically significantly lower ecm/bcm (1.11 vs. 1.28, p = 0.005). An ecm/bcm cut-off of 1.194 was 76% sensitive and 63% specific in detecting malnutrition. Conclusions: The ecm/bcm can be an indicator that detects malnutrition in patients with head-and-neck cancer. Further observations are needed to validate the significance of the ecm/bcm and to monitor nutrition interventions.

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“…The Bland‐Altman method has recently been criticized, and suggestions have been made on how to optimize its application and interpretation 74 . ‐ 77 Ludbrook 74 proposed that after plotting the differences against the averages, the next step is to evaluate if the differences are correlated with the averages and, if the P value is not statistically significant for r , then proceed with calculating the standard 95% limits of agreement.…”

Section: Validation Of Bedside Techniques To Assess Lean Tissue In CLmentioning

confidence: 99%

“…They described the repeatability coefficient as the “difference that will be exceeded by only 5% of pairs of measurements on the same subject.” 57 This would allow for evaluating not only the limits of agreement between the 2 methods but also the repeatability (ie, precision) for each method separately. Repeated measures are not always obtained in studies; Ward 75 recently provided a thought‐provoking illustration of how a modified version of that approach might be used when repeated measures are not available to better define the validity of a method, building from a method described for techniques to measure cardiac output 76 , 77 . These authors advocated for the calculation of the percentage error (PE) of the limits of agreement compared with the mean of the measurements as a way of defining a cutoff for acceptability of a method.…”

Section: Validation Of Bedside Techniques To Assess Lean Tissue In CLmentioning

confidence: 99%

“…To do this, we will need to make an assumption that the precision of the DXA was actually determined from repeat measures to get a CV of 2%. We will also assume that we do not have repeat measures by our SF‐BIA method, and thus, we can follow the recommended steps to calculate the “precision” of the SF‐BIA equation as follows 75 :

\begin{matrix} left \\ {normalPrecision}_{DXA} {normal= 2CV}_{DXA}; this we know and \\ can calculate as 2 \times 2 = 4 . \end{matrix}

\begin{matrix} left \\ {“ Precision ”}_{SF‐BIA} = {2 CV}_{SF‐BIA}; this we do not know \\ and will try to estimate in a moment . \end{matrix}

\begin{matrix} left \\ {normalPE}_{DXA - SF‐BIA} {normal= 2CV}_{DXA - SF‐BIA} \times 100; this is the percent \\ error of the difference between methods, which \\ we can calculate from Figure 2B using the limits of \\ agreement of 5.8 / mean of FFM by DXA, which we \\ will assume was determined to be 32 kg . \\ {normalThis means our PE}_{DXA - SF‐BIA} = 5.8 / 32 \times 100 = 18 % . \end{matrix}

…”

Section: Validation Of Bedside Techniques To Assess Lean Tissue In CLmentioning

confidence: 99%

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Body Composition Tools for Assessment of Adult Malnutrition at the Bedside

Earthman

2015

J Parenter Enteral Nutr

185

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Because of the key role played by the body's lean tissue reserves (of which skeletal muscle is a major component) in the response to injury and illness, its maintenance is of central importance to nutrition status. With the recent development of the Academy of Nutrition and Dietetics/American Society for Parenteral and Enteral Nutrition diagnostic framework for malnutrition, the loss of muscle mass has been recognized as one of the defining criteria. Objective methods to evaluate muscle loss in individuals with acute and chronic illness are needed. Bioimpedance and ultrasound techniques are currently the best options for the clinical setting; however, additional research is needed to investigate how best to optimize measurements and minimize error and to establish if these techniques (and which specific approaches) can uniquely contribute to the assessment of malnutrition, beyond more subjective evaluation methods. In this tutorial, key concepts and statistical methods used in the validation of bedside methods to assess lean tissue compartments are discussed. Body composition assessment methods that are most widely available for practice and research in the clinical setting are presented, and clinical cases are used to illustrate how the clinician might use bioimpedance and/or ultrasound as a tool to assess nutrition status at the bedside. Future research needs regarding malnutrition assessment are identified.

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Bioelectrical impedance validation studies: alternative approaches to their interpretation

Abstract: Alternative ways of comparing analytical methods that are in use in other branches of biomedical research may prove useful when evaluating the utility of impedance-based methods and other methods for the assessment of body composition in cross-validation studies.

Cited by 14 publications

References 23 publications

Bioimpedance at the Bedside

Bioimpedance at the Bedside

Extracellular–to–Body Cell Mass Ratio and Subjective Global Assessment in Head-and-Neck Cancers

Body Composition Tools for Assessment of Adult Malnutrition at the Bedside

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