Tandem standing duration is a rapid, sensitive and specific test of Parkinson's Disease subtype

BackgroundParkinsons Disease (PD) patients with postural instability and gait disorder (PIGD) subtype are at increased risk for falls compared to the tremor-dominant subtype. We aimed to establish an easy clinical balance tool to rapidly and reliably identify PIGD patients, potentially important for directing healthcare resources or research phenotyping. Methods45 consecutive patients with PD completed clinical testing including Romberg, tandem stance, single leg stance, 360{degrees} turning and 10-meter walking. MDS-UPDRS part II and III, collected as part of regular follow-up, was used to classify disease subtype. Multinominal logistic regression models were fitted to find optimal subtype predictors and compared using receiver operating characteristic (ROC) curves. ResultsUnassisted tandem stand duration and time to turn 360{degrees} were significantly different between PIGD and tremor dominant subtypes. Both tandem standing and 360{degrees} turning showed very high predictive accuracy to predict PD subtype with an area under the ROC curve (AUC) of 86.6% and 88% respectively, which increased to 91.4% by combining both measures. Optimal cut-off values for identifying PD subtypes were tandem standing less than 20s and 360{degrees} turning longer than 6.5s. ConclusionTandem stand duration and 360{degrees} turning are easy to apply clinical tests that rapidly identify PD patients with PIGD subtype with high sensitivity and specificity. These findings may be useful in the clinic to identify PD patients current falls risk or screening for research studies. Plain Language SummaryBalance problems and falls are common in late-stage Parkinsons Disease, affecting nearly 70% of patients 10 years post-diagnosis. In contrast, Parkinsons patients who complain mainly of shaking (tremor) are less liable to fall. We set out to find an easy and reliable bedside test to distinguish patients at risk of falls with early Parkinsons. This is important so that resources can be targeted to patients in need of support such as physiotherapy and fall prevention. 45 patients with Parkinsons disease participated in this study and completed a battery of balance tests completed within the time of their regular follow-up appointment. We found that tandem standing duration - a test where patient stand still in the heel-to-toe position - and time taken to complete a full circle, were highly reliable in detecting patients with balance and gait problems. Specifically, patients with balance and gait problems were unable to tandem stand for more than 20 seconds and took more than 6.5 seconds to turn a full circle. Together, these two tests that take a minute to complete in the clinic, and may help improve the care for patients with Parkinsons as a quick screening tool to identify Parkinsons disease at risk of falls.