Psychometric validation of the German Cancer Worry Scale as a patient-reported outcome measure in individuals undergoing genetic testing for hereditary cancer risk

Abstract Background Cancer worry is a key psychosocial outcome among individuals undergoing genetic testing for hereditary cancer risk, yet validated patient-reported outcome measures (PROMs) in the German-speaking context are limited. We aimed to evaluate the psychometric properties of the German version of the 8-item Cancer Worry Scale (CWS) in a clinical registry-based cohort. Methods In this cross-sectional study, German-speaking adults undergoing genetic testing were recruited from the ATHENA hereditary cancer registry. Structural validity, internal consistency, test–retest reliability, construct validity, and floor and ceiling effects were assessed in accordance with COSMIN recommendations for PROM validation. Predefined hypotheses were used to evaluate construct validity. Results A total of 202 participants (median age 41 years, 93% female) were included. The CWS demonstrated high internal consistency (Cronbach’s α = 0.87) and a one-factor CFA supported its unidimensional structure (CFI = 0.986, TLI = 0.980, RMSEA = 0.048, SRMR = 0.033). Test–retest ICC was 0.86 (95% CI 0.73–0.93). CWS scores correlated positively with anxiety (τ=0.44) and depression (τ=0.27), and inversely with mental well-being (τ=−0.29), and showed a smaller correlation with physical health (τ=−0.10). Evidence for known-groups validity was inconclusive. Conclusion The German 8-item CWS demonstrated sufficient structural validity and internal consistency, with a good test-retest reliability point estimate and partial support for the predefined construct validity hypotheses. Evidence for known-groups validity remains inconclusive. Further studies are warranted to establish responsiveness and clinically meaningful thresholds before routine clinical implementation.