Blood Bank Case Study: “What’s Your Type?”

The general public doesn’t always know a lot about laboratory testing in general, but most people know a little about blood types, even if it’s what they have learned from TV! Blood types do seem to come up in casual conversation. We might hear a conversation about blood type after someone has donated blood, or between family members comparing notes, who ask “What’s your type?” Yet, even with medical technologists, there can still be some confusion about blood types and blood typing, particularly if one has not worked in Blood Bank in many years. I recently received an email from a colleague who had a few questions about blood types, as she has not worked in Blood Bank for over 40 years. I always tell my students that no question is a bad question, and indeed, she asked some very good questions, which I will address with this case study.

  • What blood type is listed on a patient’s chart if they type “O Du”?
  • What blood type is recorded on a donated unit of blood typed “O Du”?
  • What type of blood does an “O Du” patient receive?
  • Can an “O Du” patient have a transfusion reaction if they are transfused with O positive blood? Would she need to receive O negative blood in a transfusion?
  • Does an “O Du” patient need to receive RhoGAM if she pregnant and her husband is Rh positive?

If you have ever wondered or can’t remember details about any of these questions, you’re in the right place. So, what’s new, if anything, with blood types?

Landsteiner discovered the ABO blood group system in 1901, and identified A, B and O blood types, using experiments performed on blood from coworkers in his laboratory. The discovery of the codominant AB blood type soon followed, but it was not until around 1940 that the Rh blood group was first described. In 1946, Coombs and coworkers described the use of the antihuman globulin (AHG) to identify weak forms of Rh antibodies in serum. For us old blood bankers, the original name for this test was the Coombs’ test. (You will still find physicians ordering a Coombs’ test!) The current and proper name for this is the direct antibody test (DAT), which is used to detect in vivo sensitization of RBCs. AHG can also be used to detect in- vitro sensitization of RBCs using the 2 stage indirect antibody test (IAT).

Since Landsteiner’s work, we have not discovered any new blood groups that are part of the routine blood type. The ABO and Rh blood groups are still the most significant in transfusion medicine, and are the only groups consistently reported. However, we currently recognize 346 RBC antigens in 36 systems.1 Serological tests determine RBC phenotypes. Yet, today we can also determine genotype with family studies or molecular testing. This case study and 2 part blog reviews some terminology in phenotyping, some difficulties and differences encountered, and explores the possibility of RHD genotyping to assess a patient’s true D status.

Our case study involves a 31 year old woman who is newly married. She is not currently pregnant, has never been pregnant, is not scheduled for surgery but has had a prior surgery 15 years ago, and has never received any blood products. She and her husband recently donated blood and, as first time blood donors, just got their American Red Cross (ARC) blood donor cards in the mail. The husband noted that his card says that he is type O pos. The woman opens her card, and, with a puzzled look on her face, says “My card says I’m an O Pos, too. There must be a mistake.” She knows she has been typed before and checks her MyChart online. Sure enough, her blood type performed at a local hospital is listed in her online MyChart as O negative. She further checks older printed records and discovers that 15 years ago, before surgery, she was typed at a different hospital as “O Du”. She is very upset, wondering how she can have 3 different blood types. She is additionally concerned because they are planning to have children and recalls being told that because she is Rh negative, that she would need Rhogam. Is she Rh negative or positive, and what does Du mean? Will she need Rhogam when pregnant? She has many questions and calls the ARC donor center for an explanation.

What blood type is listed on a patient’s chart if they type “O Du”?

What is happening here, what is this woman’s actual blood type, and what testing can be done to ensure accuracy in Rh typing? From the patient reports, it appears that this woman has what today we call a “weak D.” Du is an older terminology that should no longer be used, and that has been replaced by the term “weak D.” But, why does she have records that show her to be an O neg, a type O, Du (today, this would be written O weak D), and now, a card from ARC stating she is O pos?

RhD negative phenotypes are ones that lack detectable D antigen. The most common Rh negative phenotype results from the complete deletion of the RHD gene. Serologic testing with anti-D is usually expected to produce a strong 3+ to 4+ reaction. A patient with a negative anti-D at IS and at IAT would be Rh negative. If the patient has less than 2+ strong reaction at immediate spin (IS), but reacts at IAT, they would be said to have a serologically weak D.1 Historically, weak D red blood cells (RBCs) are defined as having decreased D antigen levels which require the IAT for detection. Today’s reagents can detect many weak D types that may have been missed in the past, without the need for IAT. However, sometimes IAT is still necessary to detect a weak D. When this is necessary is dependent on lab SOPs and whether this is donor testing or patient testing. The reported blood type of this patient also depends on the SOPs of the laboratory that does the testing. And, the terminology used for reporting is also lab dependent. It is not required by AABB to test patient samples for weak D (except for babies of a mother who is D negative). There is also no general consensus as to the terminology to be used in reporting a weak D. Some labs would result this patient as O negative, weak D pos. Some labs may result O pos, weak D pos. Others may show the individual reactions but the resulted type would be O pos. Labs who do not perform weak D testing would report this patient as O, Rh negative. The following chart explains why this patient appears to have 3 types on record.

Figure 1. Tube typing results of same patient from different labs with different SOPs.

What blood type is recorded on a donated unit of blood typed “O Du?”

AABB Standards for Blood Banks and Transfusion Services requires all donor blood to be tested using a method that is designed to detect weak D. This can be met through IAT testing or another method that detects weak D. If the test is positive, the unit must be labeled Rh positive. This is an important step to prevent alloimmunization in a recipient because weak D RBCs can cause the production of anti-D in the recipient. This also explains why the ARC donor card this patient received lists her type as O pos.

What type of blood does an “O Du” patient receive?

Historically, weak D red blood cells (RBCs) were defined as having decreased D antigen levels which require the IAT for detection. A patient who is serologic weak D has the D antigen, just in fewer numbers. This type of weak D expression primarily results from single-point mutation in the RHD gene that encodes for a single amino acid change. The amino acid change causes a reduced number of D antigen sites on the RBCs. Today we know more about D antigen expression because we have the availability to genotype these weak D RBCs. More than 84 weak D types have been identified, but types 1, 2, and 3 represent more than 90% of all weak D types in people of European ethnicity.2 An Rh negative patient has no D antigen and should, under normal circumstances, only receive Rh negative blood. Yet, there has been a long history of transfusing weak D patients with Rh positive RBCs. 90% of weak D patients genotype as Type 1, 2 or 3 and may receive Rh positive transfusions because they rarely make anti-D. 2

It is now known that weak D can actually arise from several mechanisms including quantitative, as described above, position effect, and partial D antigen. Molecular testing would be needed to differentiate the types, but, with the position effect, the D antigen is complete and therefore the patient may receive Rh positive blood with no adverse effects. On the other hand, a partial D patient may type serologically as Rh negative or Rh positive and can be classified with molecular testing. It is important to note that these partial D patients are usually only discovered because they are producing anti-D. If anti-D is found, the patient should receive Rh negative blood for any future transfusions.

Thus, 3 scenarios can come from typing the same patient. With a negative antibody screen, and because 90% of weak D patients have been found to be Type 1, 2 or 3 when genotyped, many labs do not routinely genotype patients and will report the blood type as Rh pos and transfuse Rh pos products. However, depending on the lab medical director and the lab’s SOPs, these same patients may be labeled Rh neg, weak D and receive Rh negative products. There is no general consensus on the handling and testing of weak D samples. The 3rd scenario is that many labs do not test for weak D in patients at all, and a negative D typing at IS would result in reporting the patient as Rh neg, with no further testing. In this case, the patient would be transfused with Rh negative products.

Can an “O Du” patient have a transfusion reaction if they are transfused with O positive blood? Would she need to receive O negative blood in a transfusion?

This question was covered somewhat in the above discussion. Policies regarding the selection of blood for transfusion are lab dependent, dictated by the lab medical director, and are based on the patient population, risk of developing anti-D, and the availability or lack of availability of Rh negative blood products. Anti-D is very immunogenic. Less than 1 ml of Rh pos blood transfused to an Rh negative person can stimulate the production of anti-D. However, not all patients transfused with Rh positive blood will make and anti-D. As discussed above, 90% of weak D patients are types 1, 2 or 3, would be unlikely to become alloimmunized to anti-D. If a weak D patient with a negative antibody screen receives a unit of D pos RBCs, there is a very small possibility that they are a genotype who could become alloimmunized to the D antigen and produce anti-D. However, as stated above, the majority of weak D patients can be transfused with D positive RBCs. Thus, with few exceptions, from a historical perspective, one can safely classify the weak D as D positive.

This question gets a little trickier when dealing with females of childbearing age. We particularly want to avoid giving Rh positive blood to females to avoid anti-D and the complications of Hemolytic Disease of the Fetus and Newborn. Therefore, when dealing with these patients, lab policies and physicians tend to be more conservative in their approach to transfusion. The consequences, however, in males and older females are less serious and these patients could be given Rh positive blood if there exists a shortage of Rh negative units. Any patient who becomes alloimmunized to the D antigen, would thereafter be transfused with Rh negative products.

Does an “O Du” patient need to receive RhoGAM if she pregnant and her husband is Rh positive?

This, again, would be up to the medical director, the lab’s SOPs or the patient’s physician. Depending on lab practice, the lab may or may not perform weak D testing. If the lab does not perform weak D and results this patient as Rh neg, the patient would get Rhogam. If the lab does do weak D testing and finds a weak D phenotype, the decision whether or not to give Rhogam would be up to lab practices and the practitioners involved. The lab’s policy on terminology used in resulting the type may also reflect the decision whether or not to give Rhogam. This brings up a lot of questions in the lab because we know that a patient who would not make anti-D would not need Rhogam. So, what is the best course of action? Read my next blog to learn more about troubleshooting and resolving D typing discrepancies!

From the discrepancies in reported type in this individual, and putting all the pieces of the puzzle together, we can conclude that this patient is a weak D phenotype. However, the type reported and the terminology used varies from lab to lab. Molecular testing is available, yet most labs are still using serological testing for blood types for both donors and patients. This is based on several factors within the lab setting. Stay tuned for my next Blood Bank blog exploring D typing discrepancies and the financial aspects of performing genotype on pregnant patients to clarify Rh type.

-Becky Socha, MS, MLS(ASCP)CM BB CM graduated from Merrimack College in N. Andover, Massachusetts with a BS in Medical Technology and completed her MS in Clinical Laboratory Sciences at the University of Massachusetts, Lowell. She has worked as a Medical Technologist for over 30 years. She’s worked in all areas of the clinical laboratory, but has a special interest in Hematology and Blood Banking. When she’s not busy being a mad scientist, she can be found outside riding her bicycle.

The Occurrence of Lewis Antibodies in Pregnancy

A 36 year old woman presented to the delivery room at a local county hospital at 39 weeks’ gestation. The doctor ordered a type and screen on the patient, the blood was drawn and sent to the Blood Bank lab. The Blood Bank tech looked up the patient’s Blood Bank history and noted that an antibody screen done at 28 weeks was positive, with an anti-Lea identified. The Blood Bank’s policy is to have 2 units of blood available for any patient with an antibody. As the Blood Bank tech was working on the sample, the physician sent a STAT order for 2 units RBCs for intrapartum hemorrhage.

Are Lewis antibodies clinically significant? AABB defines a clinically significant antibody as one that causes decreased red blood cell survival of transfused cells, one that causes hemolytic transfusion reaction or one that causes Hemolytic Disease of the Fetus and Newborn (HDFN).3 In the Blood Bank, we would always be cognizant of all three criteria, but in this case, we are particularly concerned with HDFN.

The Lewis system is of great interest in immunohematology because of its unique characteristics. The Lewis blood group system is the only one where the antigens are not produced by the red blood cell itself. We learn in immunohematology that red cell antigens are structures that are usually formed on red blood cell membranes, but Lewis stands alone in that the antigens are glycolipids that are formed in the plasma and then passively absorbed onto the red blood cell membrane. This forms a loose attachment and these antibodies can shed or elute off the RBCs in certain circumstances.

Because Lewis antigens are not formed on RBCs, Lewis antigens are not present at birth and therefore not found on cord blood cells. Cord blood and RBCs from newborns will phenotype as Le(a-b-). The saliva of these newborns will have Lea and/or Leb antigens depending on the genes inherited, but the RBCs will test negative for these antigens at birth. By about 10 days of age, the Lewis antigens can be detected in plasma, and they will shortly thereafter begin to be absorbed onto the RBCs. Yet, children do not exhibit their true Lewis phenotype until about age 6.

The development of Lewis antigens is also unique. Lewis antigens are not antithetical, as they result from the interaction of two fucosyltransferases encoded by the Le and Se genes. The Le gene is needed for the production of Lea antigen and the Se gene is needed to form Leb antigen. The three common Lewis phenotypes, Le(a+b-), Le(a-b+) and Le(a-b-) indicate the presence or absence of the Le and Se transferase enzymes.

In pregnancy a mother’s plasma volume increases, and because Lewis antigens are not an integral part of the RBC membrane, they can elute off her RBCs. This causes a decrease in Lewis antigen and some pregnant women, regardless of their true Lewis antigen type, will temporarily type as Le(a-b-). At the same time, because they are now typing Le(a-b-), pregnant women often acquire Lewis antibodies.

Anti-Lea is the most frequently found Lewis antibody, is IgM, and is usually detected at room temperature. In most cases, it is acceptable to give patients with Lewis antibodies RBC units that are crossmatch compatible at 37C without giving antigen negative units. One reason for this is that, as we saw above, Lewis antigens are merely absorbed onto RBCs and can be eluted from transfused red cells within days of transfusion. In addition, when Lewis antigen positive blood is given to Lewis-negative recipients, the Lewis substance in plasma neutralizes antibodies in the recipient. This is why it is extremely rare for anti-Leato cause hemolysis of transfused RBCs. Regardless of Lewis phenotype, RBCs would be expected to have normal in vivo survival.

For an antibody to cause HDFN it must be able to cross the placenta. The antibody must also react with antigens on the red blood cells. Because Lewis antibodies are IgM and do not cross the placenta, and because Lewis antigens are not present on fetal and neonatal erythrocytes, Lewis antibodies have not been implicated in HDFN and this baby is not at risk.

What does this all means in practice? Though the presence of anti-Lewis antibodies in pregnant women is fairly common, both anti-Leaand anti-Leb are naturally occurring IgM antibodies that are not generally considered to be clinically significant. They have low immunogenicity, they do not cause HDFN, they rarely cause hemolysis and do not cause decreased survival of transfused RBCs. This baby is not at risk for HDFN. The mother can safely be transfused with crossmatch compatible RBCs. Her Lea antibodies may be neutralized with a transfusion or will naturally disappear, and her true Lewis phenotype should return within about 6 weeks after delivery.

References

  1. Harmening DM: The Lewis System. In Harmening DM, (6th ed): Modern Blood Banking and Transfusion Practices. FA Davis, Philadelphia 2012, pp. 177-180
  2. Fung, Mark K, ed.: The Lewis System. 18th ed: AABB Technical manual, Bethesda, Md. 2014, pp 304-306
  3. Fung, Mark K, ed.: PreTransfusion testing. 18th ed: AABB Technical manual, Bethesda, Md. 2014, pp 376
  4. D. Radonjic et al, The Presence of antibodies in anti-Lewis system in our pregnant women. Giorn.It.Ost.Gin. Vol. XXXII-n.4.Luglio-Agosto 2010.

 

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-Becky Socha, MS, MLS(ASCP)CM BB CM graduated from Merrimack College in N. Andover, Massachusetts with a BS in Medical Technology and completed her MS in Clinical Laboratory Sciences at the University of Massachusetts, Lowell. She has worked as a Medical Technologist for over 30 years. She’s worked in all areas of the clinical laboratory, but has a special interest in Hematology and Blood Banking. When she’s not busy being a mad scientist, she can be found outside riding her bicycle.

Blood Bank Case Study: Transfusion Transmitted Malaria

Case Study

A 26 year old African American female with sickle cell anemia presented to a New York emergency room with cough, chest pain, fever and shortness of breath. Laboratory results showed an increased white blood cell count, slightly decreased platelet count and a hemoglobin of 6.2 g/dl. Her reticulocyte count was 7%, considerably below her baseline of 13%. Consulting the patient’s medical records revealed history of stroke as a child and subsequent treatment with chronic blood transfusions. She was admitted to the hospital for acute chest syndrome and aplastic crisis and care was transferred to her hematologist. Two units of RBCs were ordered for transfusion.

The blood bank technologists checked the patient’s blood bank history and noted her blood type was A, Rh(D) positive, with a history of a warm autoantibody and anti-E. The current blood bank sample confirmed the patient was blood type A, RH(D) positive with a negative DAT but the antibody screen was positive. Anti-E was identified. Per request of the hematologist, phenotypically similar units were found and the patient was transfused with 2 units of A RH(negative), C/E/K negative, HgS negative, irradiated blood. The patient’s hemoglobin rose to 8g/dl and she was discharged from the hospital 3 days after transfusion.

Ten days after discharge the patient returned to the emergency room with symptoms including aching muscles, fever and chills. A delayed transfusion reaction was suspected. A type and screen was immediately sent to the blood bank. The post transfusion type and screen remained positive for anti-E, DAT was negative. No additional antibodies were identified. However, a CBC sent to the lab at the same time revealed malarial parasites on the peripheral smear. The patient was consulted for a more complete medical history and reported that she had never traveled outside of the country. A pathology review was ordered and the patient was started on treatment for Plasmodium falciparum.

plasfal1

Discussion

Red Blood cell transfusions can be life saving for patients with sickle cells anemia. These patients are frequently transfused by either simple transfusion of red cell units or by exchange transfusion. Because of this, alloimmunization is reported to occur in 20% to 40% of sickle cell patients.1 Blood bank technologists are very diligent in adhering to strict procedures and follow a standard of practice aimed to prevent transfusion reactions. While preventing immune transfusion reactions may be the most forefront in our minds when transfusing the alloimmunized patient, it is important to consider transfusion transmitted diseases as a potential complication of blood transfusions.

Malaria is caused by a red blood cell parasite of any of the Plasmodium species. Mosquito transmitted infection is transmitted to humans through the bite of an infected mosquito. Transfusion-transmitted malaria is an accidental Plasmodium infection caused by a blood transfusion from a malaria infected donor to a recipient.

Donors, especially those from malarial endemic countries who may have partial immunity, may have very low subclinical levels of Plasmodium in their blood for years. Even these very low levels of parasites are sufficient to transmit malaria to a recipient of a blood donation. Though very rare, transfusion-transmitted malaria remains a serious concern for transfusion recipients. These transfusion-transmitted malaria cases can cause high percent parisitemia because the transfused blood releases malarial parasites directly into the recipient’s blood stream.

Blood is considered a medication in the United States, and, as such, is closely regulated by the FDA. Blood banks test a sample of blood from each donation to identify any potential infectious agents. Blood donations in the US are carefully screened for 8 infectious diseases, but malaria remains one infectious disease for which there is no FDA-approved screening test available. For this reason, screening is accomplished solely by donor questioning.2 A donor is deferred from donating if they have had possible exposure to malaria or have had a malarial infection. Deferral is 12 months after travel to an endemic region, and 3 years after living in an endemic region. In addition, a donor is deferred from donating for 3 years after recovering from malaria. It is important, therefore, for careful screening to take place by questionnaire and in person, to make sure that the potential donor understands and responds appropriately to questions concerning travel and past infection.

Malaria was eliminated from the United States in the early 1950’s. Currently, about 1700 cases of malaria are reported in the US each year, almost all of them in recent travelers to endemic areas. From 1963-2015, there have been 97 cases of accidental transfusion-transmitted malaria reported in the United States. The estimated incidence of transfusion-transmitted malaria is less than 1 case in 1 million units.4 Approximately two thirds of these cases could have been prevented if the implicated donors had been deferred according to the above established guidelines.3 While the risk of catching a virus or any other blood-borne infection from a blood transfusion is very low, a blood supply with zero risk of transmitting infectious disease may be unattainable. With that being said, the blood supply in the United Sates today is the safest it has ever been and continues to become safer as screening tests are added and improved. Careful screening of donors according to the recommended exclusion guidelines remains the best way to prevent transfusion-transmitted malaria.

References

  1. LabQ, Clinical laboratory 2014 No.8, Transfusion Medicine. Jeanne E. Hendrickson, MD, Christopher Tormey, MD, Department of Laboratory Medicine, Yale University School of Medicine
  2. Technical Manual, editor Mark K. Fung-18th edition, AABB. 2014. P 201-202
  3. https://www.cdc.gov/malaria/about/facts.html. Accessed April 2018
  4. The New England Journal of Medicine. Transfusion-Transmitted Malaria in the United States from 1963 through 1999. Mary Mungai, MD, Gary Tegtmeier, Ph.D., Mary Chamberland, M.D., M.P.H., June 28, 2001. Accessed April 2018
  5. Malaria Journal. A systematic review of transfusion-transmitted malaria in non-endemic areas. 2018; 17: 36. Published online 2018 Jan 16. doi: 1186/s12936-018-2181-0. Accessed April 2018
  6. http://www.aabb.org/advocacy/regulatorygovernment/donoreligibility/malaria/Pages/default.aspx

 

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-Becky Socha, MS, MLS(ASCP)CM BB CM graduated from Merrimack College in N. Andover, Massachusetts with a BS in Medical Technology and completed her MS in Clinical Laboratory Sciences at the University of Massachusetts, Lowell. She has worked as a Medical Technologist for over 30 years. She’s worked in all areas of the clinical laboratory, but has a special interest in Hematology and Blood Banking. When she’s not busy being a mad scientist, she can be found outside riding her bicycle.

FDA Issues Revised Recommendations for Reducing the Risk of Zika Virus Transmission through Transfusion

Today, the FDA released industry guidance for reducing the risk of Zika Virus transmission through blood products. “Revised Recommendations for Reducing the Risk of Zika Virus Transmission by Blood and Blood Components”  is for immediate implementation.