What labs need to be obtained before administering Entyvio (Natalizumab) to a patient?

Required Laboratory Tests Before Starting Entyvio (Vedolizumab)

Before initiating Entyvio therapy, patients should undergo anti-JCV antibody index testing to assess their risk of developing progressive multifocal leukoencephalopathy (PML). 1

Anti-JCV Antibody Testing

• All new patients being assessed for Entyvio should be tested for anti-JCV antibody status before initiating treatment to aid in risk stratification 1
• If the initial test is positive for anti-JCV antibodies, index testing should be performed to further quantify risk 1
• The anti-JCV antibody index is a function of a patient's anti-JCV antibody level and provides more precise risk stratification than simple positive/negative status 1

Significance of Anti-JCV Testing

• The presence of anti-JCV antibodies increases the risk of developing PML by more than 40 times 1
• Patients who test positive for anti-JCV antibodies with an index >1.5 have a significantly higher risk of developing PML (1 in 855) compared to those with lower index values 1
• Studies have shown that all available pre-PML serum samples from patients who later developed PML tested positive for anti-JCV antibodies 2

Monitoring Schedule Based on JCV Status

For JCV-Negative Patients:

• Repeat anti-JCV antibody testing every 6 months 1
• The seroconversion rate is approximately 16.2% in the first year of treatment 3

For JCV-Positive Patients:

• For patients with index ≤1.5: Repeat anti-JCV antibody testing every 6 months 1
• For patients with index >1.5: Further anti-JCV antibody index testing is not mandatory, but increased MRI monitoring is recommended 1

Additional Recommended Testing

• Baseline MRI scan before initiating therapy to serve as a reference for future comparisons 1
• C-reactive protein (usCRP) levels may be useful as a marker of JCV reactivation, as higher levels correlate with JC viruria 4
• Consider JCV DNA PCR testing in urine, as JC viruria correlates significantly with high JCV antibody index 4

Risk Factors to Consider

• Prior immunosuppressant therapy increases PML risk 1
• Duration of therapy beyond two years significantly increases PML risk 1
• Age is correlated with JCV seropositivity and JC viruria 4

Important Considerations

• The false-negative rate of anti-JCV antibody testing is approximately 2.5% 2
• Patients may remain asymptomatic for several months after developing PML lesions 1
• Early diagnosis of PML is critical in limiting permanent brain damage and improving survival rates 1
• Asymptomatic patients at the time of PML diagnosis have better outcomes (96.7% survival) compared to symptomatic patients (75.4% survival) 1