Multi-frequency bioelectrical impedance measurement in complex regional pain syndrome type I. Pilot study of 28 patients

Objectives: To evaluate the value of Multi-Frequency Bioelectrical Impedance Analysis (MFBIA) in patients suffering from Complex Regional Pain Syndrome Type I (CRPS 1). We hypothesised that patients with CRPS I have altered tissue properties in the affected limbs compared with the non-affected limbs and with limbs from unaffected individuals (control limbs). Participants: 28 patients suffering from CRPS I and in 18 healthy right-handed. Methods: Receiver operating characteristic (ROC) analyses and areas under the curve (AUC) were performed to analyse the sensitivity and specificity of the MFBIA to detect CRPS I. Results: Our data showed the phase angle (Φ), which is defined as the relation between the resistance (ability of an medium to conduct an alternating electrical current) and the reactance (resistive effect due to capacitance produced by tissue interface and cell membrane) was decreased in the CRPS I limbs compared with both the contralateral side (p = 0.004) and limbs (p = 0.02) from unaffected individuals. The MFBIA frequency (ω₀) at which the reactance and the phase angle are maximal was increased in CRPS I limbs compared with both the contralateral side (p = 0.02) and the control limbs (p = 0.01). The sensitivity and specificity of ω₀ for detecting CRPS I in the lower limb were 0.91 and 0.85 compared with lower limbs in unaffected individuals. In the upper limb, however, sensitivity and specificity were best when the right hand in unaffected individuals was used as the control. The sensitivity and specificity of ω₀ 0.75 and 0.82 compared with right arm controls. The Φ values were 0.82 and 0.70 compared with the right arm controls. Conclusion: The tissue properties are changed in the affected limb according the MFBIA.