What's this test for?

This test is ideal if you're taking or considering TYSABRI (natalizumab) therapy for multiple sclerosis and need to understand your risk for a rare brain infection called PML. It checks whether you've been exposed to the JC virus, a common virus that usually stays dormant but can become dangerous in people on certain immune-suppressing treatments. Knowing your antibody status helps you and your care team weigh the benefits and risks of continuing this therapy.

What's included in this test?

This test looks for antibodies against the JC virus in your blood, which tells you whether your immune system has ever encountered this common virus. If the initial screen comes back positive, the test automatically runs a second step (an inhibition or index confirmation) to help clarify how strong that antibody response is. Together, these results give a more complete picture for risk-stratification purposes than a simple yes/no answer alone.

What happens after I get my results?

Your results will show up in your account along with a clear explanation of what a positive or negative antibody result means. If your result is positive, the report also includes an index value that reflects antibody levels, which is one piece of information used to estimate PML risk alongside other factors like treatment duration and past immunosuppressant use. You can download a standard lab report anytime, and if you get retested in the future, the trends feature lets you track how your antibody status changes over time. Because this test relates to an ongoing therapy decision, retesting on a regular schedule is a common next step.

How can I naturally support a healthy immune system while on MS therapy?

While antibody status to JC virus can't be changed through lifestyle, keeping your overall immune system resilient is still worthwhile. Prioritize consistent sleep, regular moderate exercise, a balanced diet with enough protein and vitamin D, and stress management, since chronic stress can affect immune function. Avoid unnecessary use of other immune-suppressing substances or supplements without checking how they might interact with your MS treatment plan.

When will I get my results?

Results are typically ready within about 7 days of your blood draw. You'll be notified as soon as your report is available in your account, where you can view the antibody status and, if applicable, the index value. If you need results sooner for a treatment decision, plan your blood draw with that turnaround time in mind.

Who should consider this test?

This test is meant for people with multiple sclerosis who are currently taking, or thinking about starting, TYSABRI (natalizumab) therapy. It's also relevant if you've previously used other immune-suppressing treatments, since that history factors into overall PML risk. It is not designed for general population screening or for diagnosing an active infection.

What does a positive JC virus antibody result mean?

A positive result means your immune system has been exposed to the JC virus at some point, which is very common and does not mean you have or will develop PML. It does, however, factor into your overall risk profile if you're on or considering natalizumab therapy, especially combined with the antibody index level, prior immunosuppressant use, and treatment duration. This information is best used alongside your full treatment history to weigh ongoing therapy decisions.

What does a negative JC virus antibody result mean?

A negative result means no antibodies to JC virus were detected at the time of testing, suggesting a lower estimated risk of PML while on natalizumab. However, antibody status can change over time, so a negative result today doesn't rule out future exposure. Because of this, periodic retesting is often recommended for people who remain on long-term therapy.

How often should I retest?

Many people on ongoing natalizumab therapy retest every 6 months, since JC virus antibody status can change over time and risk estimates rely on current information. If you've recently tested negative but continue treatment long-term, regular retesting helps keep your risk profile up to date. Your treatment plan and history may call for a different schedule, so use this as a general guideline.

What should I do if my results raise concerns?

If your results show a positive antibody status with a high index value, don't panic — this is one input among several used to estimate risk, not a diagnosis of PML. Keep track of any new or unusual neurological symptoms, such as vision changes, weakness, or confusion, and seek medical care urgently if these appear, since early recognition of PML symptoms matters. Otherwise, use your result, along with your treatment history, to inform ongoing conversations about your MS therapy plan.

Getting your blood test with us is easy, private & backed by the power of science.Long story short: In the test options, use the filters or search box to narrow your choices and find the test you want. If you need a hand navigating through options, text our super friendly support team at 754-799-7833, and we'll provide tailored suggestions to help you find the ideal test. Once your order is placed, we’ll create your doctor’s lab order remotely, without any need for you to make a trip to a doctor in person or to talk to the doctor. Expect to receive your doctor’s lab order right in your inbox. It will also be in your patient portal if you need to find it later. We’ll also include instructions regarding fasting and other requirements for your test. Your patient portal will be auto-created hassle-free during checkout. If this is your first time ordering, you'll be prompted to create a password for instant login access to your patient portal. It's a quick way to conveniently access your orders and results whenever you want. When you’re ready, visit one of our 4,000 locations. Just bring your ID – no printing or faxing of your lab order is needed, as your order and details will already be in the lab system. Note that most lab locations don’t accept walk-ins, so it’s best to book an appointment in advance. Don’t worry – we’ll provide detailed instructions along the way. You’ll get your results via email & SMS and dive into understanding your body better. Yup, that easy! If you have any questions, please text us at 754-799-7833 or email support@privatemdlabs.com and we'll gladly help you.

How do I know which test to get?

In the test options, find the test you want. If you’re not sure which test to get, we can lend a hand in finding the right option. Just text or call us at 754-799-7833, email us at support@privatemdlabs.com, and we'll gladly help you. We've got your back and reply quickly.

When will my lab results be available?

Most test results will be available within 1–3 business days. Once they're ready, we'll send an email and text message to let you know. After your blood draw, just hang tight and don't worry – we'll keep you updated and in the loop! If you have any further questions, please text us at 754-799-7833 or email support@privatemdlabs.com, and we'll gladly help you.

Is it possible to make changes to my lab order if I made a mistake with the name, date of birth, or any other details?

Absolutely! We totally understand that errors can happen. No worries, we're here to help you. Just reach out to us via text at 754-799-7833 or shoot us an email at support@privatemdlabs.com. Remember to include your order number and let us know the correct information you’d like to update. Our awesome team will jump right in and make sure everything is sorted out and accurate for you. There are no changes necessary if your address is wrong on the requisition though. We don’t mail anything out. Our lab requires an address to be listed to generate an order.

Do you accept health insurance?

Only HSA & FSA is accepted. Our services are strictly self-pay and cannot be submitted to your health insurance provider except for Health Savings Accounts or Flexible Savings Accounts. This policy applies to all insurance companies, including federal health insurance programs like Medicare. If you have any questions, please text us at 754-799-7833 or email support@privatemdlabs.com.

Can I cancel my order?

Yes. We get it – sometimes your needs change. As long as your samples haven’t been collected yet, we’re happy to help you cancel your order. If you have any further questions, please text us at 754-799-7833 or email support@privatemdlabs.com. You can read more about our cancellation policy here.

How can I find a lab location near me?

During the ordering process, you’ll be able to select a specific lab near you, with no strings attached! You can switch it up later easily and visit any of our authorized locations as long as it’s the same lab company you selected your test for (Quest Diagnostics or Labcorp). Before you proceed with your order, feel free to browse through all our lab locations here. This will give you the peace of mind of knowing that there's a lab nearby your home, office or your favorite gym. If you have any questions, please text us at 754-799-7833 or email support@privatemdlabs.com and we'll gladly help you.

JCV Antibody Test - Tysabri PML Risk Screening

Getting your blood test with us is easy, private & backed by the power of science.

Long story short:

In the test options, use the filters or search box to narrow your choices and find the test you want.
If you need a hand navigating through options, text our super friendly support team at 754-799-7833, and we'll provide tailored suggestions to help you find the ideal test.
Once your order is placed, we’ll create your doctor’s lab order remotely, without any need for you to make a trip to a doctor in person or to talk to the doctor. Expect to receive your doctor’s lab order right in your inbox. It will also be in your patient portal if you need to find it later. We’ll also include instructions regarding fasting and other requirements for your test. Your patient portal will be auto-created hassle-free during checkout.
If this is your first time ordering, you'll be prompted to create a password for instant login access to your patient portal. It's a quick way to conveniently access your orders and results whenever you want.
When you’re ready, visit one of our 4,000 locations. Just bring your ID – no printing or faxing of your lab order is needed, as your order and details will already be in the lab system.
Note that most lab locations don’t accept walk-ins, so it’s best to book an appointment in advance. Don’t worry – we’ll provide detailed instructions along the way.
You’ll get your results via email & SMS and dive into understanding your body better. Yup, that easy!

754-799-7833

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