A sensitivity comparison of clinical tests for postural instability in patients with Huntington's disease

Falls are a common complication in Huntington's disease (HD) and detection of postural instability (PI) may be useful for identifying patients who are at risk of falls. The aim of our study was to find the most sensitive clinical test for PI in patients with HD and to correlate PI with the other symptoms. 20 HD patients were examined using: (1) The Unified Huntington's Disease Rating Scale (UHDRS), (2) The Mini Mental State Examination (MMSE) and (3) six clinical tests for PI. Inter-scale and test correlations were inspected and uni-dimensionality, validity, and measurement precision were analyzed using a factor analysis model/latent PI score. PI was compared with information obtained from surveys completed independently by patients and caregivers, and both reports were evaluated for absolute agreement using intraclass correlations (ICCs). PI was found in 16 patients; the tests correlated better with caregivers' reports (r=0.78) than patients' responses. The validity of the patients' answers decreased with the level of MMSE scores. PI correlated with MMSE (r=0.64, p<0.01), the subscale score for voluntary movements (r=0.86, p<0.01), the overall motor subscore (r=0.73, p<0.01), and the Luria test subscore (r=0.87, p<0.01). The stance with feet close together and tandem gait correlated best with the latent PI score, and factor loadings confirmed they were the most sensitive tests for PI detection in HD.