Analytical Validation of Cxbladder® Detect, Triage, and Monitor: Assays for Detection and Management of Urothelial Carcinoma

Background: Cxbladder® assays are reverse transcription-quantitative polymerase chain reaction (RT-qPCR) tests incorporating five genetic biomarkers (CDK1, MDK, IGFBP5, HOXA13, and CXCR2) to provide risk stratification for urothelial carcinoma (UC) in patients with hematuria or undergoing surveillance for recurrent disease. This study evaluated the analytical validity of the Cxbladder Detect, Triage, and Monitor assays. Methods: Pre-specified acceptance criteria, including the assays’ fundamental aspects (sample and reagent stability, RNA extraction quality, RT-qPCR linearity, and analytical sensitivity and specificity), accuracy and precision, and reproducibility between laboratories. Results: Cxbladder had an analytical sensitivity of 12.5–31.1 RNA copies/mL urine for the CDK1, MDK, IGFBP5, and HOXA13 UC biomarkers and 68.9 RNA copies/mL for the inflammatory biomarker CXCR2. All the pre-specified analytical criteria were met. Cxbladder had diagnostic sensitivity, specificity, positive predictive value, and negative predictive values of 77%, 94%, 68%, and 96%, respectively, for Detect; 95%, 46%, 20%, and 98% for Triage; and 91%, 39%, 21%, and 96% for Monitor. Cxbladder had high analytical accuracy (≤10.63% inaccuracy across all biomarkers) and good reproducibility (>85% concordance between laboratories). Conclusions: Cxbladder accurately and reproducibly detects UC biomarker expression and can aid clinicians in risk stratification of hematuria patients or those undergoing surveillance for recurrent UC.