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

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).

This study compared two tests, STRATIFY JCV™ DxSelect™, and IMMUNOWELL ™ JCV antibody tests, for assessing the risk of PML in patients diagnosed with relapsing- remitting 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 antibody 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.

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™ JCV antibody test 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 Cohen's Kappa coefficient, was substantial (κ=0.6222).

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.