Reliability of static balance test in faller and nonfaller parkinson disease patients

Little is known about the reliability of center of pressure (COP) variables during static balance test in patients with Parkinson's disease (PD). Furthermore, reliability studies on fallers and nonfallers PD patients have not been explored. Therefore, our study investigated the test-retest reliability of COP outcome measures in faller and nonfaller PD patients. Eighty-one PD patients (49 nonfallers and 32 fallers) were recruited for measurement of static balance test. The patients maintained double-leg stance with feet on a force plate as stably as possible. To analyze the test-retest reliability of each COP outcome measures, intraclass correlation coefficient (ICC) statistical method was performed. Among COP outcome measures, mean velocity had the highest ICC value in faller patients (ICC=0.881-0.915) and nonfaller patients (ICC=0.928-0.960). Mean distance had excellent reliability in medio-lateral (ML) direction in both faller patients (ICC=0.922) and nonfaller patients (ICC=0.921). Ellipse area had excellent reliability in nonfaller patients (ICC=0.862), but less reliability in faller patients (ICC=0.607). Our results demonstrate that objective and quantitative balance assessment method is reliable in PD patients with or without a history of falls. On the other hand, it was not appropriate to use ellipse area to assess postural balance for faller PD patients. Our findings could be useful to develop an optimal balance protocol and apply appropriate COP outcome measures for PD patients.