Bioelectrical impedance analysis instruments: how do they differ, what do we need for clinical assessment?

Abstract

Purpose of review: Bioelectrical impedance analysis (BIA) is a widely used, noninvasive method for assessing body composition. Recent technological advances have diversified BIA devices in terms of measurement frequency, electrode configuration, and portability. This review outlines key criteria for selecting a BIA system according to clinical or research needs.

Recent findings: Single-frequency BIA (SF-BIA) devices, typically consumer-grade with hand-to-hand or foot-to-foot configurations, are affordable and easy to use but often lack raw data access, clinical validation, and regulatory certification. In contrast, multifrequency BIA (MF-BIA) systems, especially octopolar models, enable segmental analysis and provide greater accuracy for evaluating fluid distribution and lean mass. However, they are costlier, depend on proprietary algorithms, and generally require standing measurements. In hospital settings, portable MF-BIA devices that allow supine, tetrapolar or octopolar assessments are preferable, particularly for use with bedridden patients. Across all contexts, standardized measurement protocols and access to raw parameters ( Z , R , Xc, PhA) are essential to apply accurate, population-specific predictive equations.

Summary: Reliable use of BIA requires careful consideration of device type, data accessibility, and methodological consistency. Portable, regulatory-certified MF-BIA systems with tetrapolar or octopolar configurations and access to raw data offer the most accurate and adaptable solutions for clinical and research applications.

Keywords: bioelectrical impedance analysis; body composition; electrode configuration; nutritional assessment.

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FIGURE 1

Bioelectrical impedance analysis devices vary in measurement configurations: (a) consumer-grade models typically use a bipolar foot-to-foot or hand-to-hand configuration with a single pair of current-injecting (signal) and voltage-sensing (detection) electrodes; (b) clinical-grade devices use a tetrapolar hand-to-foot configuration with two pairs of signal and detection electrodes, enhancing accuracy by reducing contact resistance between electrodes; (c) advanced systems feature an octopolar arrangement, with a pair of signal and detection electrodes on each hand and foot, allowing segmental assessment of fluid and lean mass distribution.

FIGURE 2

Schematic representation of adhesive electrode placement for tetrapolar and ipsilateral bioelectrical impedance analysis in the supine position: (a) upper limb: the current-injecting (signal) electrode is placed over the metacarpophalangeal joints of the second and third digits, while the voltage-sensing (detection) electrode is positioned proximally over the styloid processes of the radius and ulna; (b) lower limb: the signal electrode is applied over the metatarsophalangeal joints of the second and third toes, and the detection electrode is located midway between the medial and lateral malleoli (ankle bones), over the tibiotalar region.