Psychometric evaluation of the Medication Satisfaction Questionnaire (MSQ) to assess satisfaction with antipsychotic medication among schizophrenia patients.

The Medication Satisfaction Questionnaire (MSQ) is a single-item questionnaire which evaluates satisfaction with antipsychotic medication in schizophrenia patients. This study evaluated the reliability and validity for its use in research and clinical settings. Data pooled across treatment groups (control vs. Paliperidone ER) from a randomized 6-week study were used to conduct four psychometric assessments of the MSQ: (1) test-retest reliability, (2) convergent validity, (3) known-groups validity, and (4) minimally important difference (MID). This analysis included 191 randomized subjects. Test-retest reliability was evaluated for patients with no change in satisfaction from weeks 2 to 4 and weeks 4 to 6 (ICC=0.80; 0.83, respectively). Convergent validity was demonstrated through large correlations with Treatment Satisfaction Questionnaire for Medication (TSQM) global score (r=0.72-0.77), and through small correlations with variables measuring clinical symptoms and functioning (e.g., Positive and Negative Syndrome Scale (PANSS) total score [r=-0.30 to -0.17], CGI-S [r=-0.35 to -0.27], SF-36 Physical Functioning Score [r=0.18] and side effects and extrapiramidal measures (including UKU, ESRS-A, SAS). Mean MSQ scores were significantly different between those who completed and discontinued the study, and between different satisfaction groups based on TSQM, demonstrating good known-groups validity. MID estimates for the MSQ ranged from 0.47 (standard error of measurement) to 0.58 (anchor-based method). Results suggest that the MSQ has acceptable reliability and validity, making this single-item questionnaire appropriate and easy to use in clinical research and potentially in clinical practice. A 1-point change on the MSQ may be considered clinically meaningful.