A Rasch analysis of the Harm Reduction Self-Efficacy Questionnaire in Portugal

Introduction: A high degree of self-efficacy is required from drug users if they are to adopt long-term abstinence-maintaining or harm-reducing behaviors. Our objective was to analyze the psychometric quality of the Harm Reduction Self-Efficacy Questionnaire (HRSEQ) with the Rating Scale Model (RSM), an extension of the Rasch Model for polytomous items. Methods: Participants were 419 drug dependents from both harm reduction low threshold methadone program and therapeutic community programs in Portugal (84.5% male). Results: Indicate that the original 11-category response system did not work adequately in any of the HRSEQ situations (Withdrawal, Negative emotions and Social pressure). There was no gender-related or group-related DIF and thus the findings of neither group nor gender-related difference in harm reduction self-efficacy cannot be plausibly attributed to that technical problem. Conclusions: After recoding the rating scales by collapsing the eleven categories into four, the HRSEQ scores show good model fit and psychometric adequacy. (C) 2014 Elsevier Ltd. All rights reserved.