Phase angle of bioelectrical impedance analysis as an indicator for diabetic polyneuropathy in type 2 diabetes mellitus.

CONTEXT:Due to the heterogenous clinical symptoms and deficits, the diagnosis of diabetic polyneuropathy (DPN) is still difficult in clinical routine leading to increased morbidity and mortality. OBJECTIVE:We studied the correlation of phase angle (PhA) of bioelectrical impedance analysis (BIA) with clinical, laboratory and physical markers of DPN to evaluate PhA as possible diagnostic method for DPN. MATERIALS AND METHODS:In this cross-sectional observational study as part of the Heidelberg Study on Diabetes and Complications we examined 104 healthy individuals and 205 patients with type 2 diabetes mellitus (T2D), amongst which 63 had DPN. The PhA was calculated from multi-frequency BIA. Nerve conduction studies (NCS), quantitative sensory testing (QST) and diffusion-weighted magnetic resonance neurography (MRN) to determine fractional anisotropy (FA) reflecting peripheral nerve integrity were performed. RESULTS:T2D patients with DPN had lower PhA values (5.71 ± 0.10) compared to T2D patients without DPN (6.07 ± 0.08, p = 0.007,  + 6.1%) and healthy controls (6.18 ± 0.08, p < 0.001,  + 7.9%). Confounder-adjusted analyses showed correlations of the PhA with conduction velocities and amplitudes of the peroneal (β=0.28; β=0.31, p < 0.001) and tibial nerves (β=0.28; β=0.32, p < 0.001), Z-scores of QST (thermal detection β=0.30, p < 0.05) and the FA (β=0.60, p < 0.001). ROC analysis showed similar performance of PhA in comparison to mentioned diagnostic methods. CONCLUSION:The study shows that PhA is in comparison to other test systems used, at least an equally good and much easier to handle, investigator independent marker for detection of DPN.