How (and why) to get tested for CMV

As long-time readers of this blog will know, I’m not a fan of cytomegalovirus (CMV), a herpesvirus that is usually asymptomatic, but causes all sorts of bad things like immune aging and birth defects.

Over the last few months I’ve been following Moderna’s efforts at making a CMV vaccine. It seems like they’re having some success at inducing antibodies against CMV and hopefully these will provide protection from infection. The full Phase 3 trial is probably going to be completed sometime in the next few years. Initially it will likely be prescribed only to women of reproductive age,¹ but I’m hoping that I could eventually receive it myself. But if I already had CMV, there wouldn’t be much point in trying to avoid infection until I could get the vaccine.

So, I wanted to get tested for CMV. But how could I get tested, given that the test requires a prescription and I didn’t have one? The first thing I thought of was to see if the blood bank at Boston Children’s Hospital, where I regularly donate, would be able to test my blood. However, it turns out that they don’t perform CMV testing on their donations. I was a bit surprised by this, but apparently if they remove all the white blood cells from the blood sample they can nearly eliminate the risk of transmitting CMV even if the donor is positive.

I also thought of making my own PCR-based test, and I even designed PCR primers for this, but I realized the sensitivity wouldn’t be high enough, as CMV+ people tend to have a low viral load if the virus is latent and not actively replicating.

After a bit of searching, I found a website called Request a Test where you can directly get a test order with a diagnostic lab. After paying $65, I got an appointment at a local Quest Diagnostics site. At the site, a phlebotomist took a blood sample from my arm, and Quest tested it for anti-CMV antibodies.²

The day after my appointment, I got an email from Request a Test, which I nervously opened.

To my relief, it turns out I don’t have CMV. I was expecting to be CMV positive, given the amount of things I stuck in my mouth as a 3-year old in daycare.

So, why might you want to get tested for CMV? There are two main reasons: first, if you want to avoid infecting other people, and second, if you want to know whether you could benefit from a future vaccine. And at $65 for a test (and probably an hour of time traveling to the site and getting tested), it isn’t too much trouble to get tested.

1. If a pregnant woman is infected, CMV can cause birth defects in the fetus.

2. If you have antibodies against CMV, unless you’re a vaccine trial participant it means you are CMV positive.