Intra- and inter-rater reliability and validity of the Ottawa Sitting Scale: a new tool to characterise sitting balance in acute care patients

Purpose. We present the new Ottawa Sitting Scale (OSS) developed to characterise sitting balance in the acute care setting with slow to recover patients. We provide intra-and inter-rater reliability measures of the OSS as well as a factor analysis of scale items. Method. Seventy-one subjects aged 21-92 years participated in this study. Original scores were compared to scores from videotaped original sessions. Performance on the OSS was compared to performance on the Berg Balance Scale (BBS) and the Physiotherapy Functional Mobility Profile (PFMP). Results. The intra-class correlation coefficient (ICC) obtained for intra-rater reliability was excellent at 0.99 with individual item ICCs ranging from 0.746 to 0.997. Similarly, the ICCs for inter-rater reliability were also excellent at 0.96 to 0.98 with individual item ICCs ranging from 0.723 to 0.985. In the factor analysis, two main factors accounted for 77.8% of the total item variance and could be reasonably identified as movement within base of support (BOS) and movement outside BOS. The BBS and the PFMP had floor effects for the subjects with the lowest OSS scores while there was an OSS ceiling effect corresponding to those with BBS scores of approximately 10 or more. Conclusions. The OSS discriminates between those subjects with low levels of sitting balance. Further studies will determine responsiveness to change, and compare the OSS with other postural control measures to identify the unique application of the OSS through the stages of recovery and rehabilitation.