A cerebellar degeneration‐related protein 2‐like cell‐based assay for anti‐Yo detection in patients with paraneoplastic cerebellar degeneration

Abstract

Background and purpose: Commercially available tests for Yo antibody detection have low specificity for paraneoplastic cerebellar degeneration (PCD) because these assays use cerebellar degeneration-related protein 2 (CDR2) as the antigen, not CDR2-like (CDR2L). We aimed to test the hypothesis that use of a CDR2L cell-based assay (CBA), as an additional screening technique, would increase the accuracy of Yo-PCD diagnosis.Methods: An in-house CBA to test for anti-CDR2L antibodies was developed and used to screen sera from 48 patients with confirmed anti-Yo-associated PCD. Fifteen non-Yo PCD patients, 22 patients with ovarian cancer without neurological syndromes, 50 healthy blood donors, 10 multiple sclerosis, 15 Parkinson's disease, and five non-paraneoplastic ataxic patients were included as controls. Sera were also tested by western blot analysis using recombinant CDR2 and CDR2L proteins developed in house, by the commercially available line immunoassays from Ravo Diagnostika and Euroimmun, and by the CDR2 CBA from Euroimmun. Results:The CDR2L CBA identified all 48 patients with Yo-PCD. No CDR2L CBA reaction was observed in any of the control sera. The western blot technique had lower sensitivity and specificity as sera from eight and six of the 48 Yo-PCD patients did not react with recombinant CDR2 or CDR2L, respectively. Conclusions:The CDR2L CBA is highly reliable for identification of Yo-PCD. Although our findings indicate that, currently, the combination of CDR2 and CDR2L yields the most reliable test results, it remains to be evaluated if a test for single anti-CDR2L positivity will serve as a sufficient biomarker for Yo-PCD diagnosis.

CDR2 and CDR2L line blot performance in PCA-1/anti-Yo paraneoplastic autoimmunity

“…Limitations of our study include missing clinical data for some subjects, and the focus on line blots currently used commonly in clinical practice. Future studies will need to examine promising CDR2L cell-based assays in a similarly high-throughput laboratory practice (10). In addition, our sensitivity assessment was undertaken using PCA-1/Yo IFA criteria as the gold standard rather than clinical cohorts.…”

“…CDR2-like (CDR2L) is now recognized as another major antigen in PCA-1/Yo autoimmunity and, perhaps, the main antigen (8,9). Testing utilizing CDR2L line blot or cell-based assay has been reported to have improved performance characteristics over CDR2 (6,10). Here, we compared the performance of CDR2 and CDR2L antigens in a line blot format among six patient and control groups (among over 3,000 tested).…”