Screening for intellectual disabilities: a validation of the Hayes Ability Screening Index for in-patients with substance use disorder

Background: There is a reason to believe that many individuals with substance use disorder (SUD) in contact with services have an undiagnosed intellectual disability (ID). Assessing ID in persons with SUD can be challenging due to the influence of substances, time consumption, and specific requirements for the education of the assessor. On the other hand, an undiagnosed condition may lead to a lack of treatment adjustment and may result in drop-out from treatment or lack of treatment effect. There is a need for a time-saving, valid instrument to detect possible ID among people with SUD.

Aims: To validate the Hayes Ability Screening Index (HASI) as a screening instrument for identifying ID in a population of in-patients with SUD using all three ICD-10/DSM5 criteria in classifying ID as the validation criterion.

Methods: Eighty-four SUD in-patients aged 19–64 participated in this multicenter study. An ID was diagnosed according to the ICD-10 using WAIS-IV, Vineland II, and self-reported childhood learning difficulties.

Results: HASI correlated well with both the WAIS-IV and Vineland II. At the recommended cut-off score, the HASI had a sensitivity of 100% and a specificity of 65.4%. A large number of the false positives had IQ or both IQ and adaptive scores in the borderline range.

Conclusions: The HASI has good convergent, discriminant, and overall construct validity in detecting ID in in-patients with SUD.