Sensory Cutoff Value for Predicting Postural Instability in People with Peripheral Neuropathy Secondary to Diabetes

Abstract

People with peripheral neuropathy (PN) secondary to diabetes have higher risks of falls due to loss of the somatosensation of the feet. The purpose of this study was to investigate the cutoff values of the vibration threshold and the monofilament test to predict postural instability. Ten healthy younger adults, ten healthy older adults and ten people with PN secondary to diabetes were recruited in this study. A handheld bio-thesiometer and a set of monofilaments were used to measure the vibration threshold (VT) and tactile sensitivity (TS), respectively. VT and TS were measured at six different sites on the plantar surface, including big toe, 1st metatarsus, little toe, 5th metatarsus, middle arch, and calcaneus (heel), plus the lateral and medial malleoli. Subjects also underwent a Sensory Organization Test (SOT) to identify postural instability, defined as equilibrium scores less than age matched norms. Linear regression was used to determine which site(s) was able to predict the balance test performance. Receiver operating characteristic curves were used to compute the VT and TS cutoff values associated with postural instability. A cutoff value of 10V for lateral malleolus VT was able to predict postural abnormality with 100% Sensitivity and 54.5% Specificity. A cutoff value of 3.61 for middle arch TS was able to predict postural abnormality with 100% Sensitivity and 86.4% Specificity. Postural instability appears earlier than the current recommended clinical cutoff values for peripheral neuropathy (25V for VT and 5.07 for TS). Although current cutoff values of the vibration threshold and the monofilament test are useful for detecting a propensity for neuropathic foot ulcer, they may not be adequate for detecting early postural instability. Fall prevention strategies may be needed early in the progression of PN. Disclosure N. Aung: None. S.A. Meardon: None. C. Lin: None. R.J. Tanenberg: None.