Psychometric Validation of the KDQoL-36 in Dialysis Using Item Response Theory and Computer Adaptive Testing

Background Health-Related Quality of Life (HRQoL) is a critical outcome in end-stage kidney disease care. The Kidney Disease Quality of Life-36 (KDQoL-36) is widely used but presents limitations in length and personalization, which may reduce its clinical utility. We evaluated the psychometric performance of a multidimensional Item Response Theory (IRT) model for KDQoL-36 and simulated a Computerized Adaptive Testing (CAT) version in a large European dialysis cohort. Methods We included 8,325 KDQoL-36 responses from chronic dialysis patients in 170 NephroCare clinics across six countries. Psychometric properties were assessed using confirmatory factor analysis and bifactor IRT modeling. CAT simulations were conducted to evaluate reliability and burden reduction. Construct and criterion validity were assessed using hospitalization outcomes and known-group comparisons. Results Bifactor models demonstrated superior fit for both SF12 and disease-specific KDQoL-36 domains, with excellent reliability (ω > 0.90). IRT-based scores showed high agreement with classical test theory (R²: 0.75–0.98) and differentiated patient groups by hospitalization risk. CAT simulations showed strong agreement with full-length scores (R²: 0.93–0.99), reduced item count by 22–36% and saved up to 10 workdays per survey cycle. CCAT administered 7.67 ± 2.58 items per patient in SF12 domain and 18.75 ± 4.09 for KDQoL-36 diseases specific domain while preserving measurement precision. Conclusion Multidimensional IRT modeling supports the KDQoL-36 as a reliable, valid measure of HRQoL in dialysis care. CAT implementation offers substantial efficiency gains with minimal loss of information, reducing patient and staff burden while enhancing integration of HRQoL into routine clinical practice.