Before a blood transfusion, it’s vital to confirm that the donor blood and the recipient blood are compatible. Giving someone incompatible blood can trigger severe, even life-threatening reactions.
Pre-transfusion testing includes several steps: ABO and Rh typing, antibody screening, and crossmatching. These tests help identify potential problems before a transfusion happens. But what do “type and screen” and “type and cross” (or crossmatch) mean, and when should each be used?
This article will cover the differences between a type and screen versus a type and cross, and explain when each test is most appropriate. By understanding the proper use of these tests, we can optimize blood bank resources and ensure the best possible care for patients who need transfusions.
Background: ABO and Rh Blood Groups
Before we dive into the specifics of type and screen versus type and cross, it’s important to understand the basics of ABO and Rh blood typing. These are the two most important blood group systems when it comes to blood transfusions.
ABO Blood Types
Your ABO blood type (A, B, AB, or O) is determined by whether or not you have A and B antigens on the surface of your red blood cells. If you’re type A, you have A antigens. If you’re type B, you have B antigens. If you’re type AB, you have both. And if you’re type O, you have neither.
Importantly, your body develops antibodies against any ABO antigens you don’t have. That’s why ABO incompatibility is a huge deal. Transfusing the wrong type of blood can cause a serious, even fatal, reaction. In fact, it’s considered a “never event” in medicine. As little as 10mL of incompatible blood can trigger a severe reaction.
RhD Antigen
The RhD antigen is another key protein found on red blood cells. If you have it, you’re RhD-positive; if you don’t, you’re RhD-negative. Like with ABO blood types, it’s crucial to match RhD status during transfusions.
Ideally, RhD-negative individuals should only receive RhD-negative blood. Giving RhD-negative patients RhD-positive blood can cause them to develop antibodies against the RhD antigen (alloimmunization). RhD-positive people, on the other hand, can safely receive either RhD-positive or RhD-negative blood.
How to order pre-transfusion testing
Pre-transfusion testing always starts with a clear, accurate request from a doctor. The request has to include the patient’s information, the type of blood product needed, and why the patient needs a transfusion.
It’s also essential to understand the difference between a “Type and Screen” and a “Type and Cross” order.
Order a “Type and Screen” when you think the patient might need a transfusion. Order a “Type and Cross” (or crossmatch) when the patient definitely needs one. This tells the blood bank whether to prepare a specific unit in advance.
Patient Identification and Sample Collection
To prevent errors, it’s critical to correctly identify the patient and collect the sample with care.
Here’s what you need to know:
- Patient identification: Always ask patients to state their full name and date of birth before collecting any sample.
- Sample collection and labeling: Collect the sample in the presence of the patient and label it right away. Make sure blood samples aren’t hemolyzed (meaning the red blood cells haven’t broken open). Use the right kind of blood collection tubes, usually EDTA tubes.
Following these steps helps ensure you get accurate results.
Pre-Transfusion Testing Procedures
Before receiving a blood transfusion, your blood will undergo a series of tests to make sure the donated blood is a good match for you. Here’s a look at the basic procedures:
ABO and Rh Typing
The goal of ABO and Rh typing is to determine your ABO blood group (A, B, AB, or O) and your RhD status (positive or negative). A manual test takes about 15 minutes to complete.
Technicians test your red blood cells with anti-A, anti-B, and anti-D reagents. These reagents will react depending on whether the corresponding antigens are present in your blood.
Antibody Screening
Antibody screening looks for any unexpected red blood cell antibodies in your plasma. This test takes roughly 30 to 60 minutes.
Your plasma is mixed with a panel of reagent red blood cells that have known antigen profiles. If you have antibodies in your plasma, they’ll bind to the antigens on the reagent red blood cells, which causes agglutination (clumping) or hemolysis (destruction of red blood cells).
Antibody Identification
If the antibody screening finds something, antibody identification is performed to figure out exactly what kind of antibodies are present.
In this test, your plasma is tested against a larger panel of reagent red blood cells. This panel contains a wide range of antigen specificities. Antibody identification is especially important when antibodies are detected, as it helps ensure you receive blood that is compatible with your specific antibody profile.
Crossmatching: Ensuring Compatibility
Crossmatching is the final step in pre-transfusion compatibility testing. It’s the procedure that determines whether the donor’s red blood cells are a good match with the recipient’s plasma.
There are two main types of crossmatching: serological and electronic.
Serological crossmatch
A serological crossmatch involves mixing the recipient’s plasma with the donor’s red blood cells and then watching to see if agglutination (clumping) or hemolysis (destruction of red blood cells) occurs. This method is used when the patient’s blood contains significant antibodies.
Electronic crossmatch
An electronic crossmatch is a computer-based method that compares the recipient’s ABO and Rh type, along with antibody screening results, with the donor’s ABO and Rh type. This method is used when the antibody screen is negative.
Within these two types of crossmatches, there are a couple of different ways of doing them:
- Immediate spin crossmatch. This is a fast method that’s used when the patient has no history of clinically significant antibodies.
- Antiglobulin crossmatch. This type of crossmatch is used when the patient has a history of clinically significant antibodies or if the antibody screen came back positive.
Type and Screen vs. Type and Cross: Which one should you choose?
The choice between a type and screen and a type and cross depends on a few factors. Here’s a quick rundown:
Type and Screen
- Includes ABO and Rh typing, plus antibody screening.
- It’s best when a blood transfusion is unlikely.
- It helps the blood bank save blood for patients who absolutely need it.
Type and Cross (Crossmatch)
- Includes ABO and Rh typing, antibody screening, and a crossmatch.
- It’s best when a transfusion is likely or about to happen.
- It makes sure compatible blood is ready when the patient needs it.
So, what helps you decide? Think about these things:
- The patient’s health
- How likely they are to need blood
- How much blood is available
- Your hospital’s rules
By considering these factors, healthcare providers can choose the right approach, ensuring patients receive the appropriate blood transfusion support when they need it most.
Emergency Release of Unmatched Blood
Sometimes, doctors need to give blood immediately even if they don’t have time to complete all the usual tests. This might happen if you’re losing a lot of blood and your life is in danger. Think massive hemorrhage.
In these situations, hospitals typically use O-negative red blood cells. Because O-negative blood doesn’t have any antigens, it’s considered the “universal donor” and is less likely to cause a reaction. O-positive blood may be used for men and women who can no longer have children.
If there’s time, the medical team should still draw a sample for a type and screen before they give you any unmatched blood. Regardless, you’ll be watched very closely during and after the transfusion to make sure everything goes smoothly.
Frequently Asked Questions
What is a type and screen for pregnancy?
During pregnancy, a type and screen is a routine blood test to determine your blood type (A, B, AB, or O) and Rh factor (positive or negative). It also screens for antibodies in your blood that could potentially harm the fetus. This is crucial for preventing Rh incompatibility issues.
Do you need a type and screen for blood transfusion?
Yes, a type and screen is absolutely essential before any blood transfusion. It verifies your blood type and screens for antibodies to ensure the donated blood is compatible with your own. This minimizes the risk of a potentially fatal transfusion reaction.
What is the difference between type and screen and crossmatch?
A type and screen is a preliminary test to determine your blood type and check for common antibodies. A crossmatch is a more specific test where the potential donor’s blood is directly mixed with your blood to see if there’s a reaction. Crossmatching is done only when a transfusion is likely and identifies the most compatible blood units.
What is a type cross?
“Type cross” is not a commonly used or medically accurate term. It’s likely a shortened, informal way of referring to either a “type and screen” or a “crossmatch.” If you hear someone use this term, clarify whether they mean the initial blood typing and antibody screen, or the more specific crossmatch compatibility test.
Putting It All Together
Pre-transfusion testing is essential for safe blood transfusions. Mistakes in this process can have devastating consequences for patients. Therefore, healthcare providers need to understand the differences between “type and screen” and “type and cross” and adhere to established protocols.
Accurate patient identification and proper sample collection are crucial. It’s also important for clinicians to understand when each test is appropriate. A “type and screen” is a preliminary assessment that can be done when the need for a blood transfusion is possible, but not yet definite. A “type and cross” is a more comprehensive test performed when a transfusion is likely, matching the patient’s blood with specific donor units.
Ongoing education and training are also essential for healthcare professionals involved in blood transfusions. Advances in technology and automation are continuously improving the efficiency and accuracy of pre-transfusion testing, but knowing when and how to use these technologies appropriately is key.