Noninvasive diagnosis of bladder carcinoma by enzyme-linked immunosorbent assay detection of CD44 isoforms in exfoliated urothelia

The expression of variant isoforms of the adhesion molecule CD44 is correla ted with the onset of neoplasia in many carcinomas. We have previously show n that noninvasive detection of bladder carcinoma is possible by analysis o f anomalous CD44 expression in exfoliated urothelia, Although the sensitivi ty and specificity values obtained for the detection of bladder tumors usin g RT-PCR and Western blotting methods were superior to those obtained using urine cytology, the application of such techniques is inconvenient for rou tine diagnostic use. We now report the design and development of a sandwich -ELISA system for the reliable detection of CD44 protein extracted from sed imented urothelial cells in voided urine. Naturally micturated urine sample s were obtained from 53 patients with newly diagnosed bladder cancer and fr om 65 subjects with no evidence of disease; patients with gross hematuria w ere excluded because of interference with the assay. To demonstrate the dia gnostic potential of the system, a "gate" was imposed at N (max), i.e., the highest absorbance value obtained from a sample known to be tumor free. Al l values above this value were assumed to be indicative of the presence of a tumor. Using this parameter, 42 of 53 (81.1%) patients with histologicall y confirmed bladder tumors were correctly diagnosed. Correspondingly, under these conditions, the assay is 100% specific for tumor detection, with a s ensitivity of 81.1%, which equates to a positive predictive value of 100% a nd a negative predictive value of 81.1%. A further 54 patients who had prev iously received treatment for bladder cancer hut were currently clinically disease-free were also investigated. Of these, 47 of 54 (87%) were correctl y diagnosed to be tumor-free, which in this group equates to a positive pre dictive value of 87% and a negative predictive value of 100%. The data pres ented demonstrate that the rapid and accurate detection of elevated levels of CD44 protein isoforms in exfoliated urothelial cells is applicable to th e identification and monitoring of primary and recurrent bladder cancer.