Remember, it’s just a screening test
Pregnant patients are offered blood tests to identify the chance of certain genetic conditions, such as Down syndrome, and the predicted sex of the pregnancy, if desired. These blood tests are considered screens. The purpose of a screen is to identify pregnancies that are more likely to have a genetic condition and then offer more robust diagnostic testing either while the person is still pregnant or after birth.
Screening is not limited to the pregnancy context; we experience screening in various situations. For instance, when you go to the airport, your carry-on luggage is screened by X-ray machines. Bags that appear to have suspicious items are flagged, and a TSA agent will physically search the bag.
Most of the time, the TSA agent finds a harmless item, and you continue on your way. Rarely, they find an item that is harmful and discard it (or worse). It's important to note that you may have had the same item as the person who was flagged, but you weren't flagged. The reason for this is that screening is not perfect; it can unnecessarily flag someone's bag and sometimes neglect to flag someone's bag. The point is to assess as many bags as possible and identify those most at risk for having a harmful item.
Similarly, in pregnancy screening, the goal is to screen many pregnancies and identify those most likely to have a genetic condition. Sometimes the screen doesn't identify the pregnancy as having an increased chance, when, in fact, it does, and sometimes it identifies the pregnancy at an increased chance when, in fact, the pregnancy does not.
This is why screening can increase or decrease chances but never eliminate them.
A recent story highlights the importance of recognizing the limitations of genetic testing, particularly screening. A technical error caused a lab to report the incorrect sex for about 40 cases. This means that a person received a result stating their pregnancy would be a genetic female, but in reality, the result should have said genetic male.
It's important to maintain a healthy perspective on screens. While they can provide some information, at the end of the day, they are not perfect. As with any test in healthcare, people are involved, and mistakes can be made. It can be challenging to remember this when the message from labs is consistently: "pregnant patients have access to safe, accurate, and accessible prenatal screening" and "highly accurate results," so stories like the one linked are important reminders of the reality of screening.
* This blog constitutes general information about genetic testing and medical screening. This blog does not offer or provide medical advice or diagnosis, and nothing in this blog should be construed as medical advice or diagnosis. Do not rely on the information in this blog/article to make medical management decisions. Please consult with a medical professional before making those decisions. Do not delay in seeking professional medical advice if you think you have a medical concern. Do not disregard professional medical advice based on any information received in this blog.
