Sonja Mensch

65 Design and content validity purpose of the instrument (item 1, 2, 3 and 4) were positively assessed using the expert focus group, by formulating the clinical suitability criteria and by using the results of the pilot study on applicability in which experts, others than the expert focus group, participated. Extraordinary care was taken to follow a comprehensive step-by-step procedure to insure good content (item 5). Movakic’s content validity was thus scored as adequate. DISCUSSION Strengths of our approach to instrument development include highly experienced therapists, structuring the instrument and using a repeated consensus procedure, participated in the development of Movakic. By using this approach, it is highly likely that all relevant items of all relevant measurement properties are included, contributing to the content validity of the new instrument (Mokkink et al., 2012). However, since content validity is a subjective judgment, the developers cannot perform a completely unbiased judgment. Evaluation of content validity by a separate expert panel would contribute to the quality of the validity (Lynn., 1986) (Beck & Gable., 2001) (Mastaglia, Toye, & Kristjanson., 2003) of Movakic. Therefore other experts, who were not involved in the development of Movakic, participated in a pilot study and were asked to evaluate the relevance and comprehensiveness of the items of the new instrument. The design of Movakic takes group-specific characteristics into account, which positively impacts the construction of the test. In addition the clinical criteria are formulated by clinical experts and based on the activity level (ICF-CY) (World Health Organization., 2008). Completion of a questionnaire by the therapist based on the child’s performance during a longer time frame has the advantage of no extra burden of separately testing the child. It might be argued that flaws in caregiver recall, on whichmuch of the judgments in this study are based, may lead to inaccuracies in caregiver judgments. However, the contact between caregiver and child is very intensive, and anecdotal evidence suggests that in the care for this target group, caregivers are able to recall many (often minute) details about the care for and the condition of their clients. Experience of the physical therapist with this specific group of children and longer familiarity with the child play an essential role in effective application of Movakic. We do not expect that recall bias played an important role. This studymade an important step in the availability of an applicable, relevant and complete instrument. Movakic can be applied in a clinical setting because the construct is based on consensus of experts working in the field. In the Netherlands, most of these children visit day-care centers, where specialized on-site treatment is offered on a more