Comparing STRATIFY JCV™ DxSelect™ and IMMUNOWELL™ JCV IgG Tests in RRMS to Assess PML Risk

Background: The risk of developing progressive multifocal leukoencephalopathy (PML), a rare but potentially fatal opportunistic infection of the Central Nervous System caused by the J.C. virus (JCV), remains a primary concern associated with natalizumab therapy in the clinical management of patients diagnosed with multiple sclerosis (MS). Materials and methods: This study compared two tests, STRATIFY JCV™ DxSelect™, and IMMUNOWELL ™ JCV IgG, for assessing the risk of PML in patients diagnosed with relapsingremitting multiple sclerosis (RRMS) who had received disease-modifying therapy (DMT) with branded natalizumab (Tysabri®). The main objective was to determine the comparability of these tests in classifying PML risk. Eligible patients were selected from a database, and all specimens for the STRATIFY JCV™ DxSelect™ and IMMUNOWELL™ JCV IgG tests were collected on the same day. Patients were classified into three risk categories (low, intermediate, or high) based on threshold values for each test. Results: The analysis showed 85.5% agreement between the two tests for risk classification. Ten discordant cases were identified, mainly between intermediate- and high-risk categories. Compared to STRATIFY JCV™ DxSelect™, IMMUNOWELL™ tended to categorize more patients as higher risk. No significant association was found between discordance and prior use of immunosuppressant drugs and >24 doses of natalizumab. The agreement between tests, assessed with the weighted Kappa coefficient, was moderate (κ=0.6222). Conclusions: Compared to the STRATIFY JCV™ DxSelect™, the IMMUNOWELL™ JCV test tends to place more patients in higher risk categories. Further, longitudinal studies are needed to evaluate the clinical impact of these differences in PML risk assessment.