Reliability of the ISO wheelchair cushion test for loaded contour depth

Standardized test methods that report cushion characteristics and performance can simplify cushion selection by helping clinicians and users identify types of cushions that may meet a user's needs. The loaded contour depth (LCD) test is one of the test methods included in the International Organization for Standardization (ISO) standards for wheelchair cushions. LCD measures the depth of immersion into a cushion. The objective was to determine the reliability of LCD and overload deflection measurements. LCD and overload deflection tests were repeated on 17 cushions. Intraclass correlation coefficient (ICC) and repeatability coefficient (RC) were calculated. The reliability of LCD (ICC = 0.98; RC = 0.21) and overload depth (RC = 0.15) were very high. LCD measures can reliably be used to differentiate cushions that vary by at least 1 cm. The overload test can be used as a criterion-referenced measure, but it is not sensitive to variation.