New evidence for content validity of the German version of the Acute Cystitis Symptom Score: cognitive interview study among patients and experts

Abstract Purpose: The Acute Cystitis Symptom Score (ACSS) is a well-established and clinically validated instrument to assess symptoms and quality of life in women with uncomplicated urinary tract infections (uUTIs). A previous study examining the content validity of the German version of the ACSS has shown some methodological limitations when rated against the criteria for content validity of the COnsensus-based Standards for the Selection of Health Measurement INstruments (COSMIN) initiative. Extending the existing evidence, the present study aimed to assess the content validity of the German version of the ACSS according to the criteria of the COSMIN methodology. Methods: In individual cognitive interviews following a structured, standardized interview guide, women with a history of uUTI and experts from different medical fields rated the instructions, items, response options and recall period of the ACSS in terms of relevance, comprehensiveness and comprehensibility. Results: A total of 14 patients and 14 experts participated in two rounds of interviews. Both patients and experts rated the overall relevance and comprehensiveness of the instrument as appropriate. Modifications were primarily made to improve comprehensibility. Ten items underwent minor modifications or were given examples to enhance comprehensibility, and the scales of five items were linguistically revised. Conclusions Based on comprehensive qualitative assessments, the findings of the present study show that the ACSS is valid for the assessment of symptoms and quality of life in women with uUTIs. Modifications of the instrument concerned comprehensibility issues. Psychometric validation of the modified version of the ACSS is indicated.