Development of the Hypertonia Assessment Tool (HAT): a discriminative tool for hypertonia in children

The aim of this study was to develop a tool to identify paediatric hypertonia subtypes.

Items generated by experts were subscaled (spasticity, dystonia, rigidity). The tool was administered to 34 children (19 males, 15 females, mean age 8y 2mo, range 2y 5mo-18y 7mo) with hypertonia and cerebral palsy (CP) in Gross Motor Function Classification System (GMFCS) levels: I, n=7; II, n=5; III, n=7 level IV, n=7; and level V, n=8 level. Kuder-Richardson Formula 20 determined internal consistency. To assess reliability, two physicians administered the tool to 25 additional children with CP (15 males, 10 females; mean age 10y 8 mo; GMFCS levels I, n=4; II, n=3; III, n=7; IV, n=4; and V, n=7) on two occasions, 2 weeks apart. To evaluate validity, a third physician diagnosed the hypertonia by neurological examination.

The internal consistency of the spasticity items was moderate (alpha = 0.58), and dystonia was high (a=0.79). Item reduction eliminated seven of the 14 original items. The agreement of the spasticity and rigidity subscales was adequate (prevalence-adjusted bias-adjusted kappa [PABAK] ranging from moderate [0.57] to excellent [1.0]) for validity, test-retest reliability, and interrater reliability. For dystonia agreement was lower, with PABAK ranging from fair (0.30) to good (0.65). Eighty-seven per cent had spasticity and 78% had dystonia.

The Hypertonia Assessment Tool has good reliability and validity for identifying spasticity and the absence of rigidity, and moderate findings for dystonia.