Validation of a new diagnostic ELISA to detect anti-JCV antibodies in serum of patients with multiple sclerosis considering or receiving treatment with natalizumab.

BACKGROUND

Anti-John Cunningham virus (JCV) antibody testing is integral to progressive multifocal leukoencephalopathy (PML) risk stratification in patients with multiple sclerosis (MS), considering or receiving natalizumab. We report on analytical and clinical validation of the two-step ImmunoWELL JCV enzyme-linked immunosorbent assay (ELISA) for anti-JCV antibody testing in this patient population.

METHOD: Assay cut-off points were established using MS patient sera (N = 329), with a combined test strategy incorporating a screening test with a percentage inhibition test for those screening in an 'equivocal zone'. Clinical performance was evaluated in sera from 888 patients with MS (blinded) against STRATIFY® JCV DxSelect™ (the 'reference test'), with primary endpoints of sensitivity and specificity.

RESULTS

Variability (imprecision) was low (total coefficient of variation 6.5-11.3%); samples were stable, and no relevant hook effect was observed. Cross-reactivity was also analyzed. The optimized cut-off strategy achieved 96.4% sensitivity and 80.9% specificity. In the clinical validation study, sensitivity was 97.2%, specificity 74.1%, positive predictive value 83.5%, and negative predictive value 95.3%. Polymerase chain reaction-based false-negative estimates were similar between the ImmunoWELL JCV test (1.6%) and the reference test (3.3%). Reported serostatus change (17.3% vs 15.8%, respectively) and seroconversion (6.7% vs 10.1%, respectively) were comparable between assays.

CONCLUSIONS

The ImmunoWELL JCV test is a reliable two-step ELISA with high sensitivity and clinically relevant specificity versus the reference test, supporting its use to inform PML risk management in patients with MS considering, or receiving, natalizumab.