Reliability and Criterion-Related Validity of the Seated Posture Scale

Earlier, we reported development and initial testing of a rapid, low burden measure of wheelchair seated posture (the Seated Posture Scale [SPS]) for research and clinical use. The purpose of this study was to test the intrarater reliability, interrater reliability, and criterion related validity of the SPS.

We used a descriptive design to test and develop the instrument.

We used the method described by Walter, Donner, and Eliasziw to determine 46 participants were needed, from two Veterans Administration nursing homes or CLCs (community living centers). Using a digital goniometer to score rapidly and with two trained raters, we scored individual participants simultaneously and again in succession. For criterion related concurrent validity, we also scored each participant with Section 2 of the Seated Postural Control Measure for Adults. Intrarater reliability, interrater reliability, and criterion related, concurrent validity were assessed using kappa statistics for individual instrument items (and corresponding 95% confidence intervals where appropriate) and intraclass correlation coefficients (ICC) for total scores.

The intrarater intraclass correlation coefficient (ICC) was .995; interrater ICC was .80; interrater reliability kappas ranged from -.03 to .80. Criterion-related, concurrent validity kappas ranged from .13 to .91. ICC for total scores was .85.

The SPS has sufficient preliminary validity and reliability to support measurement of wheelchair-seated posture in outcomes research and clinical use.

In the future, rehabilitation nurses may use the SPS to improve management of wheelchair seated posture, to improve clinical outcomes, particularly for those who do not reposition themselves.