CLINICAL APPLICABILITY AND TEST-RETEST RELIABILITY OF AN EXTERNAL PERTURBATION TEST OF BALANCE IN STROKE SUBJECTS

We address the test-retest reliability and clinical applicability of an adapted external perturbation balance assessment, ie, the Postural Stress Test (PST). Repeated-measures were designed to assess the clinical features of a component of balance disorder in stroke. Twenty ambulatory stroke patients and 20 age-, gender-, height-, and weight-matched healthy control subjects participated in this study. Stroke patients were tested (using the adapted PST) on 4 separate days; matched control subjects were tested on one occasion. With the subject standing, backward perturbation forces were applied at the level of the center of gravity. Postural reactions to the test were scored in real-time and from videotape, from two different viewing angles, ie, 45 degrees and 90 degrees to the saggital plane. Scores (out of a maximal of 81) were ascertained using a 10-point subjective-observational scale. None of the control subjects fell during testing; four of the hemiplegic subjects fell. Subjects were protected from potential injury by a custom-designed safety harness system. For the hemiplegic subjects, intraclass correlation coefficients (ICCs), calculated as the reliability of any one occasion, ranged from 0.71 to 0.77, whereas those calculated as the reliability of the mean of the first two occasions ranged from 0.83 to 0.93. Although scores on the fourth occasion were significantly greater than those on the third occasion, both being significantly greater than those on the first and second test occasions (p < .05), differences were less than 5 points on the 81-point scale. Results suggested a learning effect over time, beginning on the third occasion, and indicated that data acquired over the first two occasions could provide a suitable baseline. Whether the 5-point difference might be clinically meaningful, is currently unclear. Data averaged over the four occasions for the stroke subjects were used to compare hemiplegic and control subjects. The two angles of viewing for the videotaped assessment produced similar scores for the stroke (t = 1.38; p > .05) and the healthy (t = 0.65; p > .05) subjects. Similarly, real-time and videotaped scores (at the 90 degrees observation angle) were similar for the stroke (t = 0.56; p > .05) and control subjects (t = 0.13; p >.05). However, videotaped (p < .01) and real-time scares (p < .01) (both at the 90 degrees observation angle) were significantly lower for the stroke in comparison with the control subjects. Left (n = 10) and right (n = 10) hemiplegic subjects did not exhibit a difference in adapted-PST scores (at 90 degrees observation angle and using videotaped data; p > .05). The adapted-PST was reliable when data were averaged for the stroke patients over at least two test occasions, It differentiated between a high-functioning stroke group and a healthy elderly group. Both angles of viewing produced similar results indicating that clinicians may choose their preferred patient observation angle. The assessment can be scored in real-time, eliminating the need for expensive videotaping equipment for assessment. (C) 1995 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation