Carrier screening vs. Orchid: what’s the difference? Genetic testing before pregnancy explained by a genetic counselor

Orchid offers advanced genetic testing for couples who want their child to have the best shot of a healthy life. “Ask a Genetic Counselor” is where we unpack how genetics impacts our everyday lives and the latest tools to help you build a healthier family.

What information does carrier screening and Orchid each offer me?

The first thing you might be wondering is, “what exactly is carrier screening?” The purpose of carrier screening is to determine if a couple has an increased risk of having a child affected with a specific rare genetic disorder. So, carrier screening helps answer questions like, “am I at risk for having a baby with cystic fibrosis or Tay Sachs?

Now you might not think this is necessary because you don’t have a genetic disorder, but the odd thing about genetics is that sometimes you can “carry” a gene that doesn’t work properly but not have any health symptoms. The point of carrier screening is to see if you and your partner are both carriers for the same genetic disorder. (Most genetic disorders screened for are autosomal recessive. There are also some X-linked genetic disorders in which only the female partner needs to be identified as a carrier for the child to be at risk.)

Carrier screening is often offered by OB-GYNs or fertility doctors. There are various genetic testing labs that offer carrier screening such as Natera, Invitae, and Sema4. It’s not to be mixed up with “prenatal screening,” which often refers to screening your baby for chromosomal abnormalities like Down syndrome during pregnancy. Chromosomal abnormalities often occur randomly during conception, which means it’s often not a genetic condition that’s inherited from you. The terms used are confusing, I know.

On the other hand, Orchid focuses on informing you on how your genetics can influence your future child’s genetic predisposition for common diseases like heart disease. These are diseases that we all likely know of someone whose health has been significantly impacted by. We’re able to assess your future child’s genetic risk by looking at many genes and genetic markers across the entire genome for both you and your partner.

Orchid reports help answer questions like, “how likely is my future child going to develop common diseases such as heart disease, diabetes, and cancer, based on my partner and I’s combined genetics?” and, “what can I do to reduce my future child’s health risks?”

For a quick overview of the differences, here’s a comparison chart. I’ll do a deeper take below.

Difference #1 - rare vs. common diseases screened

When comparing tests, it’s important to understand what is and isn’t screened for.

Carrier screening focuses on rare autosomal recessive and X-linked genetic disorders. These include conditions such as cystic fibrosis, Tay Sachs, or Fragile X syndrome — as well as many disorders you’ve likely never even heard of.

For the vast majority of couples (~99% of couples), carrier screening won’t change anything that you do before pregnancy. That’s because the chance of being an “at-risk couple” — meaning, you’re both carriers for the same recessive genetic disorder, or the female partner is a carrier of an X-linked genetic disorder — is about 1%.

The key difference between carrier screening and Orchid's Couple Report is that with Orchid, you’re much more likely to get meaningful information that can impact you and your future children down the road. Data from large-scale studies suggest that about 20% of the general population — which includes people like you and me — are three times more likely to develop at least one of the common conditions tested compared to the average.

Conditions Orchid offers screening for include:

Breast Cancer
Prostate Cancer
Heart Disease
Atrial Fibrillation
Stroke
Type 2 Diabetes
Type 1 Diabetes
Inflammatory Bowel Disease
Schizophrenia
Alzheimer’s

So, it’s much more likely to have a meaningful result with Orchid than with traditional carrier screening. With carrier screening, while it’s very valuable information for couples who are at risk, most couples don’t change any of their family building plans based on their carrier screening results. That’s because while almost all of us are recessive carriers of something, it’s rare for couples to be carriers of the same recessive genetic disorder.

Both carrier screening and Orchid, however, are screening tests, meaning they cannot give you a definitive medical diagnosis. For carrier screening, even if you are not found to be a carrier for certain rare genetic disorders, there is always a small chance that the screening test missed something. This is known as “residual risk.” For Orchid, measuring genetic predisposition tells you whether you or your future child are more or less likely to develop common health conditions than the average person (for example, being 3 times more likely to develop heart disease based on your genetics).

Difference #2 - less vs. more genetic data analyzed

Another big difference between carrier screening and Orchid is the method used to analyze your DNA. Not all carrier screening tests are created equal (I’ll go into that in a bit) but as a whole, they look at a small fraction (less than 2%) of your entire genome. Orchid uses whole genome sequencing which analyzes 100% of your genome — over three billion base pairs of DNA found in humans.

Why does Orchid sequence the entire genome?

You might wonder, “why is sequencing my partner and I’s entire genome even necessary? Isn’t that kind of overkill?”

The short answer is that for most people, there is no single “Heart Disease gene” that explains your genetic risk. Instead, in order to properly measure genetic predisposition to common conditions, you have to assess the whole landscape by looking at many genes and genetic markers combined for each condition. You can check out our post about what genetic risk means and what genetic predisposition screening can tell you.

Finding a needle in the haystack vs. assessing the whole landscape

Let’s talk about testing approach. Carrier screening works because the genetic disorders screened for are caused by a single gene not working properly.

One gene → one disorder

However, the reality of the genetic basis for the vast majority of diseases isn’t so simple. It’s not about finding a needle in the haystack. It’s about assessing the whole genetics landscape.

Many genes → risk for developing a condition

The fine print on carrier screening

If you’re interested in carrier screening, here are some things to keep in mind:

Carrier screening can either look for only a specific set of disorders (known as “targeted carrier screening”) or cast a wider net to screen for over 200 singe gene disorders (known as “expanded carrier screening.” Know what type of screening you’ve opted to do.
Carrier screening is typically carried out by one of two methodologies — “genotyping” or “sequencing.” The difference is that with genotyping, the test is looking for certain “hotspots” that are known to have disease-causing mutations. Genotyping fails to detect all carriers, especially among certain ancestry populations. In contrast with sequencing, the test looks at the entire DNA sequence of the specific gene. Sequencing can detect more carriers, but the potential caveat is that sometimes (very rarely) we don’t fully understand how specific mutations impact disease because it’s not seen very often. This detail may be relevant to you if you’re wondering, “what’s the most comprehensive type of carrier screening possible?” but also, “what’re the downsides and risks of a “bigger” test?”

Difference #3 one vs. both partners’ DNA sequenced

With carrier screening, the results are for one individual per test. So depending on your conception timeline and what your insurance covers, you need to decide whether a) you and your partner will do testing at the same time or b) just one partner will get screened first.

If you’re currently pregnant and would want to know your risk information in a time-sensitive manner, it’s recommended to screen for both partners at the same time.
If you’re not currently pregnant, you can consider carrier screening for the female partner first (since X-linked conditions are included). Nowadays though, many fertility clinics offer expanded carrier screening for both partners at the same time before fertility treatment.

So, with carrier screening, there’s more coordination and thinking involved about who to test and when. On the other hand, Orchid automatically incorporates both partner’s genetic information to see how your combined genetics can impact your future child’s health. Orchid does this by using sophisticated statistical modeling to forecast how your combined genetic background can influence your future child’s genetic predispositions for these conditions.

This means that the Orchid Couple report is 3 reports in one — 1) your future child 2) you and 3) your partner.

To sum things up

Carrier screening is designed to detect the risk of having a child with a rare genetic disorder. Most couples (~99%) aren’t at risk. However, for the ~1% of couples who are identified to be at risk, it can significantly reduce the possibility of serious childhood-onset diseases that can impact families in very unexpected, real ways. It may also especially benefit individuals with certain ancestry backgrounds such as those of Ashkenazi Jewish descent because they are more frequently carriers for disorders like Cystic Fibrosis, Gaucher, and Tay Sachs.

Orchid screening is the only preconception test able to measure genetic risk for common diseases for couples before pregnancy. A larger fraction of couples can discover risk and the disease screened for are more likely to impact your child’s long-term health. You can act on your results by electing to reduce your future child’s genetic risks through embryo screening or increasing awareness and screening for you and your future child. You have access to speak with a genetic counselor about your results and what to do next.