Psychometric evaluation of the Posture and Postural Ability Scale for children with cerebral palsy

Objective: To evaluate construct validity, internal consistency and inter-rater reliability of the Posture and Postural Ability Scale for children with cerebral palsy. Design: Evaluation of psychometric properties. Setting: Five child rehabilitation centres in the south of Sweden, in November 2013 to March 2014. Subjects: A total of 29 children with cerebral palsy (15 boys, 14 girls), 6-16years old, classified at Gross Motor Function Classification System (GMFCS) levels II (n=10), III (n=7), IV (n=6) and V (n=6). Main measures: Three independent raters (two physiotherapists and one orthopaedic surgeon) assessed posture and postural ability of all children in supine, prone, sitting and standing positions, according to the Posture and Postural Ability Scale. Construct validity was evaluated based on averaged values for the raters relative to known-groups in terms of GMFCS levels. Internal consistency was analysed with Cronbach's alpha and corrected Item-Total correlation. Inter-rater reliability was calculated using weighted kappa scores. Results: The Posture and Postural Ability Scale showed construct validity and median values differed between GMFCS levels (p<0.01). There was a good internal consistency (alpha=0.95-0.96; item-total correlation=0.55-0.91), and an excellent inter-rater reliability (kappa score=0.77-0.99). Conclusion: The Posture and Postural Ability Scale shows high psychometric properties for children with cerebral palsy, as previously seen when evaluated for adults. It enables detection of postural deficits and asymmetries indicating potential need for support and where it needs to be applied.