AHAAssisting Hand Assessment AIM The aim of this study was to scrutinize the Assisting Hand Assessment (AHA) version 4.4for possible improvements and to evaluate the psychometric properties regarding internal scale validity and aspects of reliability of a revised version of the AHA.METHOD In collaboration with experts, scoring criteria were changed for four items, and one fully new item was constructed. Twenty-two original, one new, and four revised items were scored for 164 assessments of children with unilateral cerebral palsy aged 18 months to 12 years. Rasch measurement analysis was used to evaluate internal scale validity by exploring rating-scale functioning, item and person goodness-of-fit, and principal component analysis. Targeting and scale reliability were also evaluated. For people with a congenital unilateral disability, it is natural and functional to use the well-functioning hand for unimanual tasks. However, most tasks in everyday life typically involve the use of both hands together. How efficiently the affected hand can be used as an assist, collaboratively with the preferred hand, is perhaps the most relevant aspect of hand function for people with a unilateral disability. The Assisting Hand Assessment (AHA) measures and describes how effectively children with unilateral disability, in particular children with congenital unilateral cerebral palsy (CP) or obstetric brachial plexus palsy, use their affected hand when performing bimanual tasks. In the AHA, scoring is conducted from observation of the child's spontaneous way of handling play objects that require bimanual hand use, not their best capacity to grasp, release, or manipulate objects when specifically asked to use their affected hand. This makes the AHA a measure of typical performance of the child and places it in the activity and performance domain of the International Classification of Functioning, Disability and Health. [1][2][3] Since its first publication in 2003, the AHA has had a large uptake both for clinical use, with users in 35 countries, and for research. In paediatric literature, the AHA has been described as 'setting the criterion standard in quantifying activity limitation'. 4 The AHA has been applied as a primary outcome measure to evaluate various upper limb interventions like constraint-induced movement therapy, [5][6][7] effectively and which items are not yet performed effectively but are the next in difficulty order. These items are considered to be on a level of difficulty that is a slight challenge but most likely for the child to achieve next, which makes them suitable targets for interventions. The first version of the AHA containing 22 items was developed for children aged 18 months to 6 years; 15 this was revised in 2007 to cover the age range 18 months to 12 years. 16 The AHA scale covering this age range is called the Kids-AHA and consists of the Small Kids-AHA for children 18 months to 6 years and the School Kids-AHA for children 6 to 12 years. Even though the AHA has sound psychometric properties and has...