182 Chapter 7 Items are disease-specific and ask about complaints due to hemophilia (eg, the past 4 weeks I was sad due to my hemophilia). The Haemo-QoL uses a 4-week recall period and items are scored on a 5-point Likert Scale ranging from “never” to “always”. Positively formulated items were inversely recoded and sum scores were calculated for each domain. Sum scores were transferred to transformed domain and total scores ranging from 0-100. Lower scores indicating better HRQoL. The PedHAL is a validated disease-specific instrument that assesses the self-reported limitations in activities and participation for children (4-18 years) with hemophilia [43]. The PedHAL consists of 53 items, distributed over 7 domains (sitting/kneeling/ standing, functions of the legs, functions of the arms, use of transportation, self-care, household tasks, and leisure activities and sports). The PedHAL uses a recall period of a month (eg, in the previous month, did you have any difficulty, due to hemophilia with walking short distances). Items are scored on a 6-point Likert Scale ranging from “impossible” to “never a problem”, and a response option “not applicable”. Domain scores and a summary score were calculated and converted to normalized scores ranging from 0 to 100, were higher scores represent better functioning. No scores were calculated if >50% of the items on a domain were scored as “not applicable”. 2.3. Statistical analyses The Statistical Package for Social Sciences version 26.0 was used for all statistical analyses. Descriptive analyses (means and percentages) were performed to characterize the patients. 2.3.1. Reliability & feasibility Reliability was assessed for the PROMIS instruments under IRT and for the legacy instruments under CTT. In IRT modeling, each response pattern results in a T-score and an associated reliability (SE of measurement). An SE of ≤ 4.5 corresponds to a reliability of 80%, which has been considered the minimum acceptable level of reliability for group comparisons with the PROMIS pediatric measures [40]. To assess the reliability of the PROMIS pediatric measures, the percentage of T-scores with an SE ≤ 4.5 was calculated. Internal consistency estimates (Cronbach α) were calculated to assess the reliability of the legacy instruments through CTT. To assess the feasibility of the instruments for use in clinical practice the number of items (for CAT: mean, minimum, maximum) that patients completed were described. In addition, floor and ceiling effects for all instruments were calculated. Floor and ceiling effects were presented as the percentage of the participants
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