Validation of the Full and Short-Form Self-Help Involvement Scale Against the Rasch Measurement Model

Substance use disorders (SUDs) are one of the nation's most costly problems in terms of dollars, disability, and death. Self-help programs are among the varied recovery support options available to address SUD, and evaluation of these programs depends on good measurement. There exists an unmet need for a psychometrically sound, brief, efficient measure of self-help involvement for individuals with SUD that is valid across different substances and age-groups.

Using data from 2,101 persons presenting for SUD treatment, the full 21-item Global Appraisal of Individual Needs Self-Help Involvement Scale (SHIS) and a newly developed 11-item short-form version were validated against the Rasch measurement model and each other. Differential item functioning (DIF) was assessed by primary substance and age.

Both versions met Rasch psychometric criteria. The full scale had minor misfit with no DIF for alcohol, marijuana, or opioids but a few instances of DIF for amphetamine and cocaine users as well as for age, in that youth tended to endorse several easier items more frequently than did adults. The 11-item short form had neither misfit nor DIF by substance and only minor DIF by age was highly correlated with the full version and was relatively more efficient. Criterion-related validity was supported for both.

Both the long and short versions of SHIS are psychometrically sound measures of a more comprehensive conceptualization of self-help involvement for SUDs that can be used as part of an in-depth assessment or as a short measure that lessens respondent burden.