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This case report describes the use of bioimpedance spectroscopy (BIS) to monitor changes in hydration status and cellular function in a 73-year-old male patient with non-small cell lung cancer (NSCLC) undergoing a 12-week immunotherapy course. The parameters monitored were phase angle (PA), impedance ratio (IR), and cell membrane capacitance (Cm). At week 1, the patient weighed 72.6 kg and with a PA of 4.2 degrees, an IR of 0.85 (no unit), and a Cm of 1.21 nanofarad (nF), all outside reference ranges. Throughout treatment, biompedance parameters were measured weekly. By week 12, body-weight had increased to 75.3 kg, PA to 4.8 degrees, IR to 0.82, and Cm to 2.01 nF, within or close to the mean ± SD ranges seen in healthy controls. BIS can non-invasively provide measurements of changes in hydration status and cellular function on a routine basis in the clinical setting. Continuous monitoring of these parameters may be useful as an adjunct to assess response to immunotherapy treatment of cancer patients. However, to assess the full clinical potential of these parameters in patients with NSCLC and generally, in patients with cancer, a study with a larger number of participants is required.

Figure S1. Raw impedance data in the impedance plane. Figure S2. Relationship between phase angle and participants’ age and weight. Table S1. Characteristics of the study subjects. Table S2. Clinical data for the ANS patients. (PDF 201 kb)

Bioelectrical impedance analysis (BIA) is a commonly used technique for assessing body composition in adults and children due to its simplicity, speed, and non-invasive nature. In diseases with body water disorders, there is a lack of a reliable and simple method that can provide clinicians with essential information about volume status, and it was speculated if BIA could be a suitable method. However, BIA basically faces two challenges regarding the function and use of the method, especially in relation to children. Firstly, most BIA applications use so-called prediction equations, which are typically derived from adult populations and may not be applicable for paediatric patients. Secondly, BIA requires a high degree of standardisation to ensure correctly performed measurements, which is a challenge specifically in children as a consequence of the lack of a BIA standardisation guideline.As a consequence of these challenges, we examined whether BIA parameters based on raw impedance data (rather than prediction equations) could be used as indicators of volume status in healthy children and in children with nephrotic syndrome (NS) (Paper I to III), where oedema is one of the complications of NS. In addition, we examined whether cell membrane capacitance reflects disease status (Paper II), since the parameter has been linked to cell membrane functionality, which may be altered in NS. All impedance measurements were performed with surface electrodes placed on the hand and foot. Lastly, we identified factors critical to successful impedance measurements (Paper IV) and used these to study the degree of BIA standardisation in healthy paediatric populations (Paper V).Overall, a comparison between our results and those obtained in healthy children (controls) demonstrated that the parameters studied can be used to assess changes in volume status and cell membrane capacitance in children with NS. Regarding BIA standardisation, a number of critical factors for performing valid BIA measurements in children were identified, although it was not possible to provide definitive BIA standardisation guidelines due to the scarcity of methodological studies in this research field. Furthermore, BIA studies in healthy children demonstrated a general lack of BIA standardisation, or its reporting, which hinders comparison of data between studies and could potentially lead to erroneous measurements.The overall conclusion of the dissertation is that parameters based on raw impedance data are promising, and these findings should be confirmed in other paediatric patient groups suffering from body water disturbances. The use of cell membrane capacitance resulted in very interesting information, but further studies are required to confirm its clinical relevance. Finally, an increased awareness of the importance of standardisation may hopefully provide more information on how the BIA technique ought to be applied in practice to increase the validity of measurement results and the transparency of the studies research design. It is hoped that the present findings can act as well-founded stepping-stones for an actual guideline for paediatric BIA measurements in the future.