Here at Counsyl, we know the decisions couples face in preparation for and during pregnancy can be confusing, if not downright overwhelming. Each test is a little bit different, but it’s not always obvious how they’re different — from when you should get the test to what the results mean, to what you can actually do about the results once you receive them.
Because we can test for over 100 diseases, many people who take the Counsyl test ask if this is the only test they need before and during pregnancy. When we get this question, it makes us realize that we need to do a better job of explaining what, exactly, carrier screening tests for. No single test can catch every possible disease a baby could have. Why? Because, well, there are many types of diseases with different underlying causes. Carrier screening tests for diseases where a healthy parent unknowingly passes a genetic mutation to their child. These mutations, while rarely a problem for the parent, cause a disease in their child. Diseases like this that you may have heard of include Tay-Sachs, Sickle Cell Disease and Cystic Fibrosis. For most of the diseases on the Counsyl test, both parents must be carriers for the same disease in order for there to be a risk to their children.
Counsyl feels strongly that our test should only screen for mutations that cause diseases serious enough that parents may want to make reproductive decisions based on their carrier status. We’ve put a lot of care into deciding which genes meet this requirement, and wanted to share some of our selection criteria with you, so you can understand the Counsyl test a little bit better:

1. Most are considered serious. Some of the diseases are life-threatening, like MCAD, which causes SIDS and Factor XI Deficiency, the cause of Hemophilia C. Some cause significant physical disability or significant intellectual disability. And some of the more severe diseases are all of the above, like Smith-Lemli-Opitz Syndrome.
2. A couple can do something about their carrier status. One option is pre-implantation genetic diagnosis (PGD), which can be done if a couple finds out their carrier status before pregnancy. PGD allows them to screen embryos for the disease before implantation.
3. Some have treatment that allow affected individuals to live typical or near-typical lives. In many cases, these treatments are only 100% effective if begun at birth.
4. Knowing allows parents to prepare. While some parents may choose to take no action based on positive results, for many of these diseases it can be helpful both emotionally and practically to have a number of months to prepare for a child who will need special accommodations. For example, couples who find out they are carriers of fragile X, the leading known cause of Autism, may be able to connect with community resources, educate themselves and emotionally prepare before the birth of their child.

On the flip side, here are some criteria we do NOT use to choose which genes to test for:

1. The disease is common. Many of the genetic mutations on the panel are ones that do occur frequently in a population. Cumulatively, one in four people will test positive for at least one disease on the Counsyl test. However, we do not consider frequency to be the only reason to include a disease on our test. Just think – if your baby were suffering from an ear infection, would it matter to you when she was up all night crying if 1 in 5 babies got ear infections, or if 1 in a million did? Probably not. Because our technology allows us to screen for a nearly endless number of diseases for one low price, we feel it is important to screen for known mutations even when they are rare.
2. We can catch all carriers. Counsyl is a risk-reducing, not risk-eliminating test. No carrier screen can detect 100% of carriers for all diseases. Some of the diseases we screen for can only catch a fraction of carriers, but we believe that the carriers we can detect will want to know.

At Counsyl, we don’t believe genetic testing should be confusing or expensive. We believe genetic testing should be simple, accessible and affordable. That’s why we have board certified genetic counselors to speak with you about your results and why we’re committed to keeping our prices low. If you have questions about the diseases we test for, please leave a comment below or email us at [email protected].