Smartphone Apps Provide a Simple, Accurate Bedside Screening Tool for Orthostatic Tremor (I8.011)

Abstract

Objective: Evaluate diagnostic properties of smartphone applications (Apps) as screening tools for Orthostatic Tremor (OT). Background: OT is characterized by the presence of sensation of instability while standing, associated with high frequency tremor in legs. Diagnosis is confirmed with surface EMG, but most patients go undiagnosed for many years. A simple bedside screening tool would be useful. Discrimination ability and accuracy studies of the use of accelerometers in OT diagnosis are needed. Methods: We obtained recordings (60 secs or less) using iPhones (Model 5, 5s and 6) free Apps ("LiftPulse" by LiftLabs, California, USA [App1] and "iSeismometer" by ObjectGraph LLC, New York, USA [App2]) at default settings. (Anupam Pathak, LiftLab, Google, Apple and ObjectGraph LLC were not involved in the research). iPhone was secured vertically, just above the patella using a phlebotomy tourniquet. A positive test meant: For App1, the presence of any tremor frequency peak between 12-19 Hz; and for App2, the presence of a tremor frequency in any axis between 12-19Hz. Results: 24 EMG-confirmed OT patients and 15 age-matched spousal controls were evaluated. App2 provides frequencies in all three axes individually. OT range tremor was seen in all three axes in only 2/24 patients while majority had it in 2 axes. App1 detected OT range tremor (12-19Hz) in 22/24 patients and none of the controls. (Sensitivity = 92[percnt], Specificity =100[percnt], Negative Predictive Value (NPV) =88[percnt], Negative Likelihood Ratio (NLR) <0.1). App2 detected OT range tremor in 21/24 patients and in 1/13 controls (Sensitivity=88[percnt], Specificity=92[percnt], NPV=80[percnt], NLR=0.14). When combined, 24/24 patients and 1/13 controls had OT range tremor on at least one of the two Apps (Sensitivity =100[percnt], Specificity = 92[percnt], NPV=100[percnt], NLR = 0). Conclusions: Smartphone Apps that use built-in accelerometers provide a simple, accurate and inexpensive bedside screening diagnostic tool for patients with Orthostatic Tremor.

Disclosure: Dr. Bhatti has nothing to disclose. Dr. Thompson has nothing to disclose. Dr. Hellman has nothing to disclose. Dr. Penke has nothing to disclose. Dr. Bertoni received personal compensation from Pfizer, Boehringer-Ingelheim, Novartis, Medtronic, Glaxo SmithKline,Valeant, and Mylan-Bertek as a speaker. Dr. Torres-Russotto has received personal compensation for activities with Abbvie, Allergan, Inc., the American Parkinson Disease Foundation, Lundbeck Research USA, Inc., Teva Neuroscience, Huntington Disease Society of America, Parkinson Disease Foundati