The assessment compared 3 intervention devices with 1 comparator.
3.1 Multiple frequency bioimpedance devices send small, painless electrical signals through the body by way of electrodes. The electrodes also measure the opposition to the flow of the electric current from body tissues (bioimpedance). Each of the devices included in this assessment are portable and could be used by a healthcare professional in either a clinic or the patient's home. Built-in software uses bioimpedance values to calculate parameters relating to hydration, such as volumes of extracellular, intracellular and total body water. Based on these parameters, multiple frequency bioimpedance devices can also produce estimates of a person's target dialysis weight, using models or algorithms that differ between devices. These outputs should be used with clinical assessment to make decisions about the amount of fluid to be removed during dialysis.
3.2 The BCM – Body Composition Monitor uses bioimpedance spectroscopy and measures bioimpedance across 50 frequencies between 5 and 1,000 kilohertz (kHz). The technology includes a BCM – Body Composition Monitor unit with an output display screen. It is connected by cables to disposable electrodes which are attached to the body. A computer software application is provided for further analysis, and external data storage devices (PatientCards) can be used to transfer outputs from the device to a computer using a card reader.
3.3 The device calculates parameters relating to hydration, such as volumes of extracellular, intracellular and total body water, and the ratio of extracellular to intracellular water volumes. It also estimates fluid overload using 2 physiological models adapted from techniques published by Chamney et al. (2007) and Moissl et al. (2006). This is the estimated volume that a person is above, or below, their predicted normally hydrated volume.
3.4 The InBody S10 model is a multifrequency bioimpedance device that measures bioimpedance across 6 different frequencies (1, 5, 50, 250, 500 and 1,000 kHz). The device consists of an InBody S10 unit which contains a display monitor. The unit is connected by cables to electrodes which are attached to the body. Two types of electrode can be used with this device: disposable adhesive type electrodes and reusable touch type electrodes which can be clipped to a person's hand and foot. As well as whole body measurements, bioimpedance measurements can also be made in 5 areas of the body; right arm, left arm, trunk, right leg, left leg.
3.5 The device calculates hydration-related outputs including water volumes (extracellular water and intracellular water) and ratio of extracellular to total body water. A suggested standard range of values is given, to help identify people who may be overhydrated or underhydrated. Accompanying software can estimate several suggested dry weight values for use, depending on any complications which may alter extracellular fluid volumes, such as diabetes or hypoalbuminaemia.
3.6 The MultiScan 5000 uses bioimpedance spectroscopy and measures bioimpedance across 50 frequencies between 5 and 1,000 kHz. The system consists of a bioimpedance spectroscopy hardware unit which is connected by leads to disposable electrodes. Outputs are displayed on a colour touchscreen display. Results for up to 1,000 tests can be stored on the device, with additional data storage available through a Wi-Fi or Bluetooth connection to a computer. A calibrator unit and analytical software are also provided. As well as whole body measurements, bioimpedance can also be measured in different body areas by attaching electrodes in different positions on the body.
3.7 The device calculates hydration-related parameters such as the volumes of total body water and intracellular and extracellular water, as well as the ratio of total body to extracellular water volumes. The device also displays an estimate of the volume of fluid excess or deficit in a person, which is reported as the volume of overhydration in litres. This value is estimated using models based on methods set out in published literature (Chamney et al. 2007; Moissl et al. 2006). The device can also do a bioelectrical impedance vector analysis.
3.8 The comparator is clinical assessment to determine fluid status and set, or adjust, target weights for people with chronic kidney disease who are on dialysis. Clinical assessment may include blood pressure measurements, changes in weight, the presence of oedema, assessment of residual renal function, any pre-existing cardiovascular conditions and also any reported symptoms of overhydration or underhydration (such as dizziness or nausea). There is no generally accepted gold standard for identifying a person's target weight for assessing the accuracy of the comparator or interventions.