A type and screen blood test is used to determine a person’s blood type (A, B, AB, or O) and to detect any irregular antibodies that may be present in their blood. This test is often required before certain medical procedures like surgery, blood transfusion, or organ transplant to help ensure compatibility between the patient’s blood and donor blood or organs.
Purpose of a Type and Screen Test
The main purposes of a type and screen blood test are:
- Determine blood type – Knowing a patient’s blood type (A, B, AB, or O) is important to ensure compatible blood is used for transfusion.
- Check for irregular antibodies – The test looks for antibodies that may have developed from prior exposure or pregnancy. These antibodies could react to and destroy incompatible blood or organs.
- Assess transfusion compatibility – If blood transfusion is needed, the test helps find suitable donor blood that lacks antigens that would cause an adverse reaction.
- Prepare for procedures – The test allows time to obtain properly matched blood for planned surgeries, transplants, etc. if irregular antibodies are identified.
When is a Type and Screen Recommended?
A type and screen is commonly recommended in these situations:
- Before any surgery where significant blood loss is possible
- Prior to a blood transfusion
- Before procedures like angiograms, endoscopies, or biopsies
- When planning an organ or tissue transplant
- During pregnancy, to detect any new antibodies
- Whenever antibody screening hasn’t been done in the last 3 months
Having current type and screen results on file allows for rapid blood provision if an emergency transfusion is required. Some facilities may require a type and screen within 30-90 days prior to certain procedures or surgeries as part of pre-admission testing.
What Does the Type and Screen Test for?
The type and screen blood test typically evaluates:
- ABO blood grouping – Determines blood type as A, B, AB or O.
- Rh typing – Detects presence of Rh(D) antigen on red blood cells to classify blood as Rh positive or Rh negative.
- Irregular antibody screening – Checks plasma or serum for antibodies that could react to foreign blood cells or tissue.
The ABO/Rh blood type establishes compatibility for red blood cell transfusion. The antibody screen identifies any existing antibodies made by the immune system that could attack incompatible blood. This is crucial information to guide selection of suitable blood products for transfusion or transplant.
How is a Type and Screen Test Performed?
A type and screen blood test involves two main parts – ABO/Rh typing and an antibody screen. Here is an overview of how these components are performed:
ABO/Rh Blood Typing
- A blood sample is drawn from the patient, usually from a vein in the arm.
- The red blood cells are separated from the plasma or serum.
- The red cells are mixed with antibodies against A and B antigens as well as Rh(D) antigen.
- Based on whether or not the antibodies cause agglutination (clumping), the blood type and Rh factor are determined.
- For example, type A blood reacts with anti-A antibodies but not anti-B.
Antibody Screen
- The patient’s plasma or serum is tested against sample red blood cells of known antigen type.
- This panel of test cells contains all the major blood group antigens.
- If agglutination occurs with any of the test cells, it indicates the presence of corresponding antibodies in the patient’s sample.
- If irregular antibodies are detected, further testing is done to identify their specificity so compatible blood can be selected.
These procedures use a small amount of blood, are generally completed in a few hours, and do not require any special preparation by the patient.
Reading Type and Screen Results
Results of ABO/Rh typing will clearly state the patient’s blood group, such as:
- Blood group A Positive
- Blood group B Negative
- Blood group AB Positive
- Blood group O Negative
For the antibody screen, results may be reported as:
- Negative – No unexpected antibodies detected.
- Positive – One or more clinically significant antibodies identified. Further testing will be done to specify the antibodies.
- Inconclusive – Suggests presence of an antibody but could not confirm. A repeat test may be recommended.
If the screen is positive, the report will list any irregular antibody or antibodies found. An example is “Anti-E antibody detected.” These abnormal antibodies must be identified before transfusion or transplant to prevent adverse reactions.
Normal Type and Screen Results
In most healthy adults, a type and screen blood test yields these normal results:
- ABO group – Usually A, B, AB, or O.
- Rh type – Most commonly Rh positive. Rh negative in about 15% of population.
- Antibody screen – Negative, meaning no irregular antibodies detected.
However, the following results would be considered abnormal:
- Unexpected ABO/Rh type that doesn’t match previous records
- Positive antibody screen, indicating the presence of irregular antibodies
- Inconclusive antibody screen warranting repeat testing
A positive antibody screen is the most concerning finding, as identifying incompatible blood is critical prior to transfusion. Additional specialized blood bank tests are done to pinpoint any abnormal antibodies found.
Why Perform Routinely?
There are several benefits to performing routine type and screen testing on surgical and transplant patients:
- Identifies at-risk individuals – A positive antibody screen flags patients who may require antigen-negative or specially crossmatched blood products.
- Avoids dangerous delays – Having current results avoids waiting for completion if urgent transfusion is needed.
- Reduces complications – Pre-identification of incompatibilities allows selection of suitable blood, reducing risks of hemolytic reactions.
- Provides convenience – Results within the last 3 months permits quick release of blood without repeat typing and antibody screens.
- Meets recommendations – Routine testing aligns with guidelines from blood banks and health authorities.
While costs are incurred, these are balanced by the significant benefits of detecting incompatibility issues before they cause a crisis during surgery or medical procedures when blood may be urgently required.
Risks and Limitations
The type and screen test is very safe and reliable when performed properly but does have some limitations:
- Doesn’t detect all antibodies – Very low antibody levels or recently formed antibodies may not be picked up.
- Lab errors – Inaccuracies in testing or result reporting can occur.
- Time constraints – Antibodies can form after the test. A repeat crossmatch is advised if >72 hours pass before transfusion.
- Transfusion reaction – In very rare cases, compatibility issues are missed or new antibodies form, causing a hemolytic reaction from blood transfusion.
However, when performed according to accepted blood bank standards and procedures, the type and screen provides vital compatibility information that makes transfusion and transplant much safer.
When are Further Tests Needed?
In some situations, additional testing beyond a type and screen is warranted:
- Positive antibody screen – Further testing must precisely identify any irregular antibodies detected so antigen-negative blood can be provided.
- Transfusion reaction history – Patients with prior reactions may need extended RBC antigen matching and crossmatching.
- Hematologic conditions – Those with diseases like sickle cell anemia or thalassemia often require more complete antigen typing.
- Pregnancy – An extended antibody screen is recommended in pregnant women to detect new antibodies.
One of the key reasons for doing an initial type and screen is to determine if and when more intensive blood compatibility testing is needed before transfusion or transplant.
Patient Preparation
Preparing for a type and screen blood test involves:
- Inform doctor of any previous transfusion reactions or blood cell antibodies.
- Disclose any pregnancy or recent pregnancy.
- Continue taking all regular medications.
- No fasting or other preparation required.
- Sleeve or short sleeve shirt preferred to allow access for blood draw.
- Tell phlebotomist if difficult veins or feeling dizzy with blood draws.
Results are most accurate when performed prior to any blood transfusion or pregnancy, which can stimulate antibody production. Most blood banks recommend retesting within 3 days before transfusion, if feasible.
Understanding Your Results
If your type and screen detects any clinically significant irregular antibodies, your doctor will discuss precautions needed for future transfusions or procedures. These may include:
- Requesting antigen-negative blood products lacking antigens you have antibodies against.
- More complete RBC antigen matching for transfusion.
- Crossmatching your blood against all cellular blood products before use.
- Delaying elective surgery until antigen-negative blood can be obtained.
- Monitoring closely for signs of hemolytic transfusion reaction during and after transfusion.
You can play an important role by knowing your blood type, keeping a wallet card noting any antibodies, and alerting healthcare providers to ensure properly matched blood products are used for your treatment.
When to Seek Medical Attention
In most cases, the type and screen blood test provides helpful information without direct medical consequences. However, you should seek prompt medical care if you experience:
- Shortness of breath, fever, or chills during or shortly after a blood transfusion, as these may signal a hemolytic reaction.
- Jaundice or dark urine after receiving blood, which could indicate breakdown of red blood cells.
- Allergic symptoms like rash, swelling, or wheezing during transfusion, suggesting an allergic reaction.
- Bleeding that does not stop after pressure at the blood draw site.
- Swelling, pain, warmth, or redness at the intravenous catheter site.
Notify your doctor of any concerning symptoms that arise during or following transfusion.
Bottom Line
The type and screen is a vital pre-transfusion test that determines the ABO/Rh blood type and checks for any irregular antibodies that could react to incompatible blood. This allows time to obtain properly matched blood products prior to surgeries, transplants, and other procedures where blood transfusion may be needed. Routine testing identifies at-risk patients in advance so appropriate blood components can be selected and disastrous hemolytic reactions avoided. With modern laboratory techniques, the type and screen provides accurate results and remains an essential safeguard for today’s transfusions and transplants.
| Purpose | Determine blood type and screen for antibodies |
|---|---|
| When needed | Before surgery or transfusion; every 3 months if at risk |
| Components | ABO/Rh typing; irregular antibody screen |
| Normal result | Known blood type; negative antibody screen |
| Abnormal result | Unexpected blood type; positive antibody screen |
| Preparation | Inform of blood reactions; continue medications |
