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

Abstract

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

Method: 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.

Results: 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.

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