The Multiple Sclerosis Intimacy and Sexuality Questionnaire - re-validation and development of a 15-item version with a large US sample

Background: Sexual dysfunction is common in multiple sclerosis (MS) but reliable and valid measurement in this population is needed. Objective: The objective of this research is to re-validate the Multiple Sclerosis Intimacy and Sexuality Questionnaire-19 in a large US sample. Methods: A total of 6300 MS patients from the NARCOMS registry completed the MSISQ-19. Unforced principal component analysis utilizing oblique rotation with Kaiser Normalization validated its construct validity. Results: The scree plot supported a three-component solution, with 63% of total variance explained. The components mirrored the original validation study measuring primary, secondary, and tertiary sexual dysfunction. PCA suggested the scale could be shortened to 15 items, which were found to apply equally well to males and females (with one primary item specific for each sex). The components were moderately intercorrelated (Pearson rs ranged from 0.5 to 0.67). The secondary subscale correlated most highly with self-reported disability (r (6081) = 0.44, p < 0.001), whereas the tertiary subscale correlated most highly with psychological distress (r (5992) = -.37, p < 0.001). Cronbach's alpha for the total scale (0.92) and the subscales (primary, 0.87; secondary, 0.82; tertiary, 0.91) demonstrated good reliability. Conclusion: The revised 15-item MSISQ is a reliable and valid measure of sexual dysfunction in men and women with MS.