Assessing Psychiatric Symptomatology in Adults with Intellectual Disabilities: Psychometric Properties of German Versions of the PAS-ADD Checklist and the Mini PAS-ADD

ABSTRACT Introduction Adults with intellectual disabilities (ID) face a high risk of developing psychiatric disorders, yet there is a lack of valid instruments measuring psychopathology in this population. Two existing instruments are the PAS-ADD Checklist questionnaire and the Mini PAS-ADD interview, two third-party assessments that can be used for the purpose of screening. Methods German versions of the PAS-ADD Checklist and the Mini PAS-ADD were performed on 78 and 55 adults with ID, respectively. Internal consistency, sensitivity, and specificity were calculated for both instruments and the convergent validity of the two tools was tested. Results Cronbach’s alphas of the Checklist’s scales and the total score were questionable (alpha over 0.6), except for a very low alpha for Organic Condition (0.34). For the scales of the Mini PAS-ADD, Cronbach’s alpha varied between 0.34 (Unspecified Disorder) and 0.72 (Psychosis). Using current clinical diagnoses as a reference, sensitivity was rather poor in both instruments, with a case identification of 52% each. Specificity was 70% for the Checklist and 100% for the Mini PAS-ADD. The correlation between the tools was low to moderate (Spearman’s ρ = 0.32, Kendall’s τ = 0.22). Applying the available thresholds, the instruments resulted in the same conclusion about the possible occurrence of psychopathology in only 52.7% of the cases. Discussion The PAS-ADD Checklist and the Mini PAS-ADD are feasible third-party instruments for the assessment of psychiatric disorders in people with ID. Professionals must be aware of the low sensitivity of both tools, meaning that a referral to further assessment should not be based on the thresholds alone. More research is needed as to the adjustment of the thresholds, the suitability of the unusual scoring system and the additional development of self-report instruments.