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Table 2 Description and psychometric properties of assessments used

From: Behavioural and psychological characteristics in Pitt-Hopkins syndrome: a comparison with Angelman and Cornelia de Lange syndromes

Assessment [authors] Description of assessment Scoring Psychometric properties
Wessex Questionnaire (WQ) [52] The questionnaire assesses ability in individuals with ID. The following subscales are assessed: continence, mobility, self-help skills, speech and literacy. Within the current study, “self-help” was used as a proxy measure to assess the degree of ability. On the self-help subscale, individuals are rated on their ability to feed, wash and dress themselves. For each task, they are scored on a 3-point scale. The total self-help score ranges from 3 to 9: total score of 3–5 (“not able”), 6–7 (“partly able”) and 8–9 (“able”). The scale has modest inter-rater reliability at subscale level for both children and adults ranging from 78% (self-help, literacy) to 92% (mobility) [52].
Social Communication Questionnaire Lifetime Version (SCQ) [57] The parent-report questionnaire is used to measure ASD symptomatology and is a screening tool for ASD based on the Autism Diagnostic Interview. It consists of 40 items grouped into three subscales: communication, social interaction and repetitive and stereotyped behaviours. The lifetime version is completed in regards to an individual’s full developmental history. The 40 items all require a yes/no response. Total scores range from 0 to 39. A cut-off score of > 15 indicates possible ASD and > 22 indicates possible autism. The cut-off point of > 15 was found to distinguish pervasive developmental disorder (PDD) individuals from other diagnoses with a specificity of .80 and a sensitivity of .96 (excluding individuals with ID) and distinguished individuals with autism from people with ID with a specificity of .67 and sensitivity of .96. The higher cut-off of > 22 was necessary to distinguish between autism individuals with PDD with a specificity of .60 and a sensitivity of .75. The scale has good concurrent validity with the Autism Diagnostic Interview and with the Autism Diagnostic Observation Schedule [57, 58]. Internal consistency is good [19, 57].
Sociability Questionnaire for people with Intellectual Disability (SQID) [31] The informant-based questionnaire assesses the sociability in children and adults and is appropriate for individuals with ID. The questionnaire contains 25 items including 13 categories and is to be completed regarding an individual’s typical behaviour across social situations with familiar and unfamiliar people and considers the possible indication of selective mutism. The SQID consists of 25 items, 21 are on a 7-point scale (e.g. items 1–17: range from “very shy” to “very sociable”) and four are yes/no responses. Total scores evaluate the effect of social context on an individual’s sociability with a familiar or unfamiliar person. A higher score indicates more sociability. The scale has a satisfactory inter-rater reliability for item level between .43 and .80 (Spearman’s coefficient > .60) for Q1-21. Kappa values for categorical items were .96, .44 and .51 (Q22, 24, 25). The scale also has good concurrent validity with the Child Sociability Rating Scale (CSRS [19]) (rs = .36 to .52; all p = .01).
Challenging Behaviour Questionnaire (CBQ) [36] Part one of the questionnaire assesses the presence of self-injury, physical aggression, verbal aggression, destruction of property and stereotyped behaviour over the course of the previous month. Part two assesses the severity of each type of challenging behaviour. Part one is based on a yes/no basis. Part two requires responses on a 4–5-point scale (14 items). Item scores are summed to provide an overall severity score. Lower scores indicate less severe behaviour. The scale has good inter-rater reliability (range of α = .62 to .72) [36]. Concurrent validity of the total scores of the CBQ and the Aberrant Behavior Checklist (ABC [59]) was good (0.56, p < .01) [60].
The Mood, Interest and Pleasure Questionnaire-Short Form (MIPQ) [32] The informant based questionnaire is appropriate for use for individuals with ID and assesses two main subscales of mood and interest and pleasure. The short form consists of 12 items (6 items for each subscale). Items are rated on a 5-point scale, and total scores range between 0 and 48. A higher score indicates positive affect and higher levels of interest and pleasure. The short form version of the MIPQ has good internal consistency (α total = .88; α Mood = .79; α Interest and Pleasure = .87), test-retest (.97) and inter-rater reliability (.85). Concurrent validity between the MIPQ and the ABC [59] ranged from medium to strong (0.36–0.73; p < .001).
Repetitive Behaviour Questionnaire (RBQ) [33] The informant-based questionnaire is appropriate for use for children and adults with ID and examines the frequency of repetitive behaviours over the last month. The scale consists of 19 items including five subscales: stereotyped behaviour, compulsive behaviour, insistence on sameness, restricted preferences and repetitive speech. Informants rate the frequency of each behaviour over the last month. Scores are rated on a 5-point scale from “never” (0) to “more than once a day” (5). A verbal score ranges between 0 and 76 and a nonverbal score ranges between 0 and 60 (4 items are only applicable to verbal individuals). Behaviours occurring “once a day” or “more than once a day” are deemed to be of clinical importance. A clinical cut-off is obtained if an individual has a score of three or more on at least one item within a subscale. Item-level inter-rater and test-retest reliability and validity are good Spearman’s coefficients for inter-rater reliability range from .46 to .80 at item-level (73% > .60). Spearman’s coefficients for test-retest reliability range from .61 to .93 at item level (52.6% > .80). The scale has good concurrent validity and content validity between the RBQ and the repetitive subscale of the Autism Screening Questionnaire (ASQ [57]) (.6; p < .001). There is good Internal consistency at full-scale level (α > .80) and for the stereotyped behaviour and compulsive behaviour subscales (α > .70), this was lower for restricted preferences, repetitive speech and insistence on sameness subscales (α = .50, .54 and .65) [61].
The Activity Questionnaire (TAQ) [54] The information-based questionnaire assesses behaviours that indicate overactivity and impulsivity and is suitable for use for people with ID. The questionnaire consists of 18 items grouped into three subscales: over-activity, impulsive speech and impulsivity. The score range for over-activity is 0–36, impulsive speech 0–24 and impulsivity 0–24. Impulsive speech is not calculated for individuals who are non-verbal. Items are scored on a 5-point scale of “never/almost never” (0) to “always/almost all of the time” (5) to assess activity frequency. Scores of 32 for overactivity and 24 for impulsivity are identified as “abnormally high” (at or above the 95th percentile). The scale has a good item level inter-rater reliability (mean of .56, range = .31 to.75) and test-retest reliability (mean of .75, range = .60 to .90). Inter-rater and test-retest reliability for subscales and total score were above .70 [54].
Sensory Experience Questionnaire- Short form, Version 2.1 (SEQ) [56] The questionnaire examines the frequency of sensory behaviours across sensory response patterns (Hypo-Social, Hypo-Nonsocial, Hyper-Social and Hyper-Nonsocial), five sensory modalities (Tactile, Auditory, Visual, Gustatory, and Vestibular) and across social or non-social contexts. The scale consists of 41 items (counting sub-items) rated on a 5-point scale of “almost never” (1) to “almost always” (5). A total score is obtained and sub-scores for sensory patterns (Hypo-responsiveness, Hyper-Responsiveness and Sensory Seeking), a score for each modality and for social and non-social contexts. A higher score is indicative of more severe sensory symptoms. The overall internal consistency is α = .80 [62] and for subscales Hyper-Responsiveness α = .73, Hypo-Responsiveness α = .75, Sensory Seeking α = .80, Social α = .69, Non-Social α = .78. The test-retest reliability is .92 (intraclass correlation coefficient) [63]. Concurrent validity between the SEQ and the Sensory Processing Assessment (SPA) indicated significant correlations between Hypo-Responsiveness subscales and Hyper-Responsiveness scales [64].
Health Questionnaire (HQ) [55] The questionnaire looks at the presence and subsequently the severity of 15 different health difficulties, with subsections assessing health difficulties over the entire lifetime and over the course of the last month. The scale consists of 32 items. Severity of each reported health difficulty is rated on a 3-point scale of never (0) to severe (3). An overall health score is determined by summing the total for both time periods. A higher score indicates greater severity. Inter-rater reliability for health difficulties reported across the individuals lifetime was α = 0.72 and for those present within the last month were α = 0.76. Internal consistency is found to be good (α = 0.77) for the overall health score [55].