Background: To date, specific scales for the assessment of severity of somatoform disorders are still rare. Characteristic cognitive and behavioural domains, representing severity are not incorporated in the existing scales. Results with the novel quantification inventory for somatoform syndromes (QUISS) are presented in this paper.
Methods: The QUISS has been developed as a qualified severity scale for patients fulfilling diagnostic criteria according to DSM-IV or/and ICD-10. It was designed to be particularly suitable for application in clinical trials and for monitoring the efficacy of psychotherapy and pharmacotherapy. Not only number, severity and frequency of somatoform symptoms, but also common cognitive and behavioural domains of somatoform disorders have been included into this instrument. Both an 18-item patient- and observer-rated version are available taking about 20 min to complete. The questionnaire was applied to patients with somatoform disorder (N = 96), major depression (N = 24), and panic disorder (N = 16).
Results: The psychometric properties of the scale are satisfactory. The QUISS showed high objectivity (Cronbach's alpha = 0.90 for both versions; inter-scale correlations r = 0.64-0.88; p < 0.05), good test-retest- (r = 0.87; p < 0.05) and inter-rater-reliability (r = 0.89; p < 0.05). External validity (moderately high correlations of QUISS-T to SOMS 7T (r = 0.54), significant discrimination to major depression p < 0.05) was satisfactory. Factor structure revealed five relevant factors.
Conclusions: The QUISS could be a useful instrument in somatoform disorders for the assessment of syndrome severity and treatment outcome in scientific and clinical settings.