Baby Observational Selective Control AppRaisal (BabyOSCAR): Convergent and discriminant validity and reliability in infants with and without spastic cerebral palsy.

AIM: To describe the development of an observational measure of spontaneous independent joint motion in infants with spastic cerebral palsy (CP), the Baby Observational Selective Control AppRaisal (BabyOSCAR), and to test its convergent validity and reliability.

METHOD: A retrospective sample of 75 infants (45 with spastic CP and 30 without CP) at 3 months of age were scored with the BabyOSCAR and compared with diagnosis of spastic CP, limbs affected, and Gross Motor Function Classification level at 2 years of age or later for convergent validity using t-tests, Kruskal-Wallis tests, and Spearman's rank correlation coefficients. BabyOSCAR interrater and test-retest reliability was also evaluated using intraclass correlation coefficients.

RESULTS: Infants with spastic CP had significantly lower BabyOSCAR scores than children without CP (p < 0.001) and scores were significantly correlated with Gross Motor Function Classification System levels (p < 0.001). Children with unilateral CP had significantly higher asymmetry scores than children with bilateral CP or no CP (p < 0.01). Interrater and test-retest reliabilities were good to excellent.

INTERPRETATION: Reductions in independent joint control measured in infancy are a hallmark of eventual diagnosis of spastic CP, and influence gross motor function later in childhood (with or without a diagnosis of CP).