Clinical measurement of the static rear stability of occupied wheelchairs

Objective: To evaluate a new clinical test, platform testing of the static rear stability of wheelchairs occupied by their users (using methods adapte d from the International Organization for Standardization [ISO]), from the perspective of its measurement properties, safety, and comfort. Design: Within-subject comparisons. Setting: Rehabilitation center. Patients: Ninety-seven wheelchair users. Main Outcome Measures: Static stability (with the brakes locked and unlocke d, the occupant leaning forward and back, and with antitip devices in place ), dynamic stability (the criterion measure), reliability, validity, sensit ivity, specificity, predictive values, and likelihood ratios. Results: Test-retest reliabilities (n = 18 to 24) were all >.93. The test's construct Validity was demonstrated by the finding that static stability w as appropriately affected by locking the brakes, body position, and antitip devices (p <.0001). Spearman's rank correlations between static and dynami c stability ranged from .29 to .65. Sensitivity ranged from 46% to 85%, spe cificity from 59% to 78%, positive predictive values from 76% to 86%, negat ive predictive values from 42% to 69%, positive likelihood ratios from 1.56 to 2.95, and negative likelihood ratios from .22 to .71. There were no adv erse events, and the subjects tolerated the tests well. Conclusions: In the clinical setting, the ISO platform test of static rear stability has good to excellent measurement proper ties, is safe, and is we ll tolerated. Static-stability testing in this setting should be performed in the context of a comprehensive evaluation of wheelchair safety and perfo rmance. (C) 1999 by the American Congress of Rehabilitation Medicine and th e American Academy of Physical Medicine and Rehabilitation.