A brief version of the Subjects' Response to Antipsychotics questionnaire to evaluate treatment effects.

BACKGROUND Monitoring patients' experiences with antipsychotics may help to improve medication adherence and outcome. We aimed to develop a shorter version of a comprehensive 74-item self-report questionnaire suitable for routine monitoring of desired and undesired effects of antipsychotics. METHODS Included were patients with psychotic disorders from seven mental health care organizations in The Netherlands, using antipsychotic medication, who completed the Subjects' Response to Antipsychotics (SRA-74). Exploratory factor analysis (EFA) and similarity analysis based on mutual information were used to identify the latent factor structure of the SRA. Items were reduced according to their metric properties and clinical relevance upon consensus by an expert panel, using a Delphi procedure of three rounds. We determined the internal consistency of the shorter version using Cronbach's alpha. RESULTS SRA data of N=1478 patients (mean age of 40 years, 31% females) were eligible for analysis. EFA extracted thirteen factors from the SRA-74, including four factors for desired effects (e.g. recovery of psychosis, cognition and social functioning) and nine factors for undesired effects (e.g. weight gain, flattened affect and increased sleep). Based on this solution 12 items were eliminated for statistical reasons. The expert panel eliminated another 28 items with redundant content, resulting in a 34-item version. The SRA-34 includes 10 desired and 24 clinically relevant undesired effects. Both the subscales for desired and undesired effects have a Cronbach's alpha coefficient of 0.82. CONCLUSIONS The SRA-34 can be used to evaluate desired and undesired effects of antipsychotics in routine clinical practice and research.