The Bombay Phenotype

ABO and H are the most important of the currently characterized blood group systems, since incompatibility between transfused red cells and recipient plasma leads to potentially devastating consequences. Those learning about this system spend lots of time memorizing biochemical details that can be overwhelming. In addition, exam-writers seem to enjoy asking questions about unusual entities in these systems that most blood bankers will never see in real life. Two very rare situations with altered red blood cell appearances (“phenotypes”), known as “Acquired B” and “Bombay,” are among those most frequently discussed on examinations. In a previous post, I discussed the Acquired B Phenotype (see my web page for further details and a video presentation). Today, let’s proceed with details about the very famous Bombay Phenotype.

In the 1950’s, a small group of people were identified in an area in India surrounding the city of Bombay (now called “Mumbai”) that appeared to be blood group O at first glance. As you should know from a basic understanding of the ABO system, group O individuals have antibodies against both A and B antigens, and as a result, can only receive red blood cells from donors who are also group O. The patients reported by Bhende et al (Lancet 1952;1:903-4), however, carried an extra antibody in their plasma that made them INCOMPATIBLE with others that were truly blood group O. These individuals (and others described since) lack a precursor antigen known as “H” both on their RBCs as well as in their secretions and plasma.

In brief, ABO antigens on red blood cells are made in a sequential manner. First, long sugar chains attached to either lipids or proteins (glycolipids or glycoproteins, respectively) on the surface of the RBC must be modified through the work of an enzyme encoded by the H (FUT1) gene (chromosome 19) to display H antigen activity. Only then can the chain be further modified by the action of a second enzyme that adds a single sugar to change that H antigen into either an A or a B antigen. The alleles inherited at the ABO gene site on chromosome 9 (A, B, and/or O) determine which ABO antigens will be expressed on the red cell surface, but again, such a change ONLY happens if the precursor antigen (H) is made first.

ABO antigens are unusual in that they are not only attached to RBCs, but are also present in free-floating forms throughout the body. The same manufacturing principle (first make H, then make A or B) applies to the formation of soluble ABO antigens found in virtually all bodily fluids, including plasma and saliva (and other secretions). The enzyme that is responsible for H antigen formation in these fluids is different than the one described above; it is encoded by the Se (FUT2) gene (also on chromosome 19).

If a person lacks both active forms of both the H (FUT1) and Se (FUT2) alleles (described as having the genotype hh, sese), they are incapable of making H antigen either in secretions and plasma AND on the surface of the RBC (they are described as “H-deficient non-secretors”, and commonly with the shorthand Oh). The genetic mechanism of these changes is well described in the original cohort in India (a particular single nucleotide polymorphism in FUT1 accompanied by a total deletion of FUT2), and multiple additional mutations have been identified that could lead to someone lacking active forms of both alleles.

Bombay

So, with that out of the way, what does this mean? Well, if a person lacks the ability to make H antigen in both RBC-based and free precursor chains, they will appear to be blood group O, just like someone who inherits two O alleles at the ABO site. However, unlike group O RBCs, which carry more H antigen than any other ABO group, H-deficient non-secretor RBCs have NO H antigen (this can be demonstrated easily in blood banks by showing no reaction when the RBCs are mixed with the H lectin Ulex europaeus). In keeping with the way other ABO system antibodies are formed, Bombay individuals make anti-A, anti-B, and anti-A,B, exactly like others that are group O. However, they also make a strong and very dangerous anti-H. The antibody is primarily IgM, but like most ABO-related antibodies, it reacts strongly at body temperatures, and generally is considered highly capable of giving rise to dangerous hemolytic transfusion reactions. As a result, Bombay patients can really receive blood only from others who completely lack the H antigen (which functionally means they should either get their own blood that has been stored for their future use or blood from another H-deficient non-secretor).

Bombay1

There are variants of Bombay, most notably the “Para-Bombay” phenotype in which the patient is H-deficient on RBCs, but IS capable of making ABO antibodies in secretions and plasma (these patients are H-deficient secretors). The key fact that must be evaluated in all of the Bombay-related phenotypes is whether or not an anti-H has been formed that is capable of reacting at body temperature. If so, Bombay variants must also receive only H-deficient red blood cells.

As mentioned, most workers will never see a patient with the Bombay Phenotype. This entity is seen mostly in examination world, but it is nonetheless very important for transfusion service personnel to be aware of this rare phenotype and prepared to take steps to diagnose it. I have seen reports of Bombay cases misdiagnosed as non-ABO high-frequency alloantibodies, and am aware of a case where the diagnosis became apparent when a child was born with an ABO type that seemed impossible based on the ABO types of the parents.

Chaffin

-Joe Chaffin, MD, is the new Vice President and Chief Medical Officer for LifeStream, a Southern California blood center headquartered in San Bernardino, CA. He has a long history of innovative educational efforts and is most widely known as the founder and chief author of “The Blood Bank Guy” website (www.bbguy.org).

Acquired B Phenotype

Students learning about the ABO blood group system commonly get confused about two unique situations: The Acquired B phenotype and the Bombay phenotype.

These two entities are VERY different, but they are similar in this way: people are asked about both on exams all the time, but hardly anyone every actually SEES either one in real life! It is essential for students of blood banking to understand Acquired B clearly, as it remains a real possibility in everyday practice. I’ll cover Acquired B in this month’s blog, and next month I will discuss Bombay.

Routine ABO testing is performed in two distinct (but usually simultaneous) stages, known as “red cell grouping” (forward grouping or “front type”) and “serum grouping” (reverse grouping or “back type”). Here’s an example of how it works: If a person’s red blood cells (RBCs) react strongly with reagent anti-A but not anti-B, we would interpret their red cell grouping as blood group A. If there is no ABO discrepancy, that same person’s serum should have no reaction with reagent group A1 RBCs and strong reaction with reagent group B RBCs (demonstrating the expected presence of anti-B in the serum). Thus, the serum grouping interpretation would also be blood group A, and no ABO discrepancy would exist (see this illustrated in the figure below).

aboexample

ABO discrepancies occur any time the interpretations of a person’s red cell and serum grouping do not agree. ABO discrepancy takes on many forms, and acquired B is a great, if not terribly common, example.

Students learning about the ABO blood group system commonly get confused about two unique situations: The Acquired B phenotype and the Bombay phenotype.

Usually, Acquired B occurs when the RBCs from a blood group A patient come in contact with bacterial enzymes known as “deacetylases.” These enzymes, commonly carried by bacteria that live in the colon, catalyze the removal of the acetyl group from the residue that gives the A antigen its specificity, N-acetylgalactosamine (GalNAc). This modification leaves the A-specific sugar as galactosamine (N-acetylgalactosamine with the acetyl group removed = galactosamine). Recall that normally, the group B-specific sugar is galactose.

acqb

As a result of this modification, anti-B in both human group A serum and especially certain monoclonal reagents will weakly agglutinate the group A RBCs carrying the acquired B antigen. This means that the patient’s RBCs may have a weakly positive reaction with anti-B in serum grouping tests instead of the expected negative (see image below). The serum grouping for these patients is no different from that expected for a group A individual (negative with group A reagent RBCs, strong positive with group B RBCs).

acqbabotesting

So, what does this actually mean? How do these patients actually get transfused? This is where the recognition of the entity in a transfusion service or reference laboratory is essential. Several simple strategies can be employed to prove that this patient is really NOT group AB. First, I always advise people to check the patient history! The rare cases of acquired B that are still seen will often be associated with colorectal malignancy, gastrointestinal obstruction, or gram-negative sepsis (where those bacteria can contact the RBCs). Second, adding the patient’s own serum to his RBCs (autoincubation) reveals no incompatibility. In other words, this patient’s own very strong anti-B does not recognize the acquired B antigen (which is really just a partially modified group A antigen) as being an actual group B antigen. We already know that this patient has anti-B in his serum from his serum grouping results (see above), but the patient’s own anti-B completely ignores the acquired B antigen on his RBCs (even though human anti-B from other people will react). Third, the technologist can use a different form of monoclonal anti-B in the patient’s red cell grouping test. Certain clones are known to react with acquired B, while others are not (normally specified in the package insert), and choosing a different clone (often easier in reference lab settings) will render the forward grouping consistent with that of a group A person. Also, incubating the Acquired B RBCs with acetic anhydride will lead to “re-acetylation” of the modified A antigen and loss of the B-like activity. Finally, acidifying the reaction mixture of the patient’s RBCs with human anti-B (non-self) can eliminate the incompatibility with that source of anti-B.

In the end, Acquired B is a serologic problem that is fairly easy to recognize, especially on examinations (I always tell my students that when they see a problem that starts with words like, “A 73 year old male with colon cancer…”, check the answer for Acquired B!). In real life, experienced blood bankers can diagnose and confirm Acquired B fairly easily in the rare times that it is seen. These patients can receive group A blood without a problem, and the ABO discrepancy will disappear as the infection or other situation causing causing contact with bacterial enzymes clears. Thanks for your time and attention. See you next month when I will discuss the Bombay Phenotype!

 

Chaffin

-Joe Chaffin, MD, is the new Vice President and Chief Medical Officer for LifeStream, a Southern California blood center headquartered in San Bernardino, CA. He has a long history of innovative educational efforts and is most widely known as the founder and chief author of “The Blood Bank Guy” website (www.bbguy.org).

Designer Blood

Recently scientists have discovered transcription pathways that turn pluripotent stem cells into red blood cells and white blood cells. (You can read the article here.) This could be the first step in making patient-specific blood products or a way to increase the nation’s blood supply without having to rely on volunteer donors. What do you think? Could this be the future of transfusion medicine?

What’s In a Name? Chikungunya and Dengue Viruses and the Blood Supply

“Incurable Virus Spreads in US!” In recent weeks, breathless and scary-sounding headlines like this have been seen in newspapers and web sites in the United States, describing an outbreak of emerging viruses with scary names like “Chikungunya” and “Dengue” seen in US travelers to the Caribbean, South America, and other tropical areas. While the news certainly sounds terrifying to the public, Transfusion Medicine professionals must evaluate donors carrying these “emerging” infections (defined as infections whose human incidence has increased in the last 20 years or so) as scientifically as possible to ensure the maximum safety of the blood supply. Let’s take a quick look at two of these infections and their implications for potential blood donors.

Chikungunya virus:

Chikungunya has quite possibly the greatest name in the history of viruses! Sadly, it is a fun-sounding name for a not-so-fun disease. This virus has been on our radar for a few years now, as it spread through Africa, Southeast Asia and parts of Europe. More recently, however, Chikungunya has become quite prominent in the Caribbean islands as well as Central and South America.

  • Vector: Aedes species mosquitoes
  • Spread: Human to human via mosquito vector
  • Illness: High fever, severe joint pain that may last months, severe infections in already ill adults or neonates
  • Treatment: No specific therapy or vaccine; just support symptoms
  • Blood transmission: No cases reported, though theoretically possible
  • Tests for donors: None approved by FDA

Though the CDC is monitoring numerous cases of Chikungunya in US citizens in multiple states exposed through mosquito bites during travel, we currently do not have great ways to track or test blood donors. Fortunately, at least 80% of people infected with this virus are symptomatic, and as a result, would be deferred from blood donation simply because they don’t feel well.

Dengue:

Dengue is another emerging infection that has been recently seen in US citizens, primarily those who travel to Asia and South America (in fact, according to the February 2014 update to the AABB Dengue virus fact sheet, Dengue is the most frequent cause of fever in US travelers returning from those areas; source: AABB web site). Worldwide, Dengue is a MASSIVE problem, affecting millions and killing over 22,000 people every year (source: CDC Dengue web site).

  • Vector: Aedes species mosquitoes
  • Spread: Human to human via mosquito vector
  • Illness: High fever, rash, headache, severe lower back pain known as “break-bone fever”; Rare cases with hemorrhagic or shock
  • Treatment: No specific therapy or vaccine; just support symptoms
  • Blood transmission: Multiple well-proven transmissions from RBCs, platelets, and plasma
  • Tests for donors: None approved by FDA

Dengue and Chikungunya infections can present in a very similar manner (high fever and joint pain). Dengue, however, is associated with much more severe consequences in a few patients, with diffuse hemorrhage and complete systemic collapse seen in a few patients.

Together, these viruses infect millions of people around the world every year. However, to date, neither has proven to be a large issue in US blood donors. In addition to the fact that potential blood donors infected by either virus will often be deferred because they do not feel well, many will also be prohibited from donating because they have traveled to an area where malaria is endemic (the malaria travel deferral covers much of the distribution area for both Dengue and Chikungunya).

It is clear to all Transfusion Medicine professionals that we are not completely “safe,” even though we have not yet seen an abundance of transfusion transmission of Dengue, and none whatsoever with Chikungunya. The presence of these non-treatable infections is simply another reminder that transfusion has risks aside from the ones that clinicians and patients think about most (HIV and hepatitis, for example). A big part of the job of a Transfusion Medicine professional is to help our clinician friends ensure that transfusions are only given when absolutely necessary.

 

Chaffin

Joe Chaffin, MD, is the new Vice President and Chief Medical Officer for LifeStream, a Southern California blood center headquartered in San Bernardino, CA. He has a long history of innovative educational efforts and is most widely known as the founder and chief author of “The Blood Bank Guy” website (www.bbguy.org).

 

Molecular Testing in Transfusion Medicine

Last week, the FDA approved the Immucor PreciseType Human Erythrocyte Antigen (HEA) Molecular BeadChip assay. This method determines non-ABO antigens on red blood cells and is the first molecular assay for determining blood compatibility to be approved by the FDA.

What do you think, blood bankers? When it comes to blood compatibility, do you trust molecular diagnostics as much as serological methods?

Stocking Shelves

My struggle in the community hospital setting is having the appropriate inventory for the patient population I need to serve. When I stocked the refrigerator during my golf club days the oldest inventory went up front and the new product went to the back. Later in graduate school I learned that was the FIFO method of inventory management. Blood Bankers have a unique twist thrown our way in that as blood sits on our shelves certain things happen that make an older unit less desirable than one collected a few days prior. The life span of a red cell is around 100-120 days depending on which literature you cite. Our job as blood bankers is to get the freshest blood to each patient we serve, so inventory management becomes more of an art than science.

Let’s take first the type specific debate. Some will say always transfuse type specific blood; if the patient is type A then the patient receives type A blood. Some will say to give whatever is most fresh; if we have fresh O cells an A person will get O. What I found when I first came to be the supervisor in my blood bank is that we were outdating a lot of type A blood. So instead of just decreasing the amount of type A, I also increased the number of type O I had on my shelf. This allowed me to be more flexible; I would give out more O when my inventory of A was low. Also, the blood I was giving out was always fresher than before I changed the inventory.

Let’s take this another direction. My policy states that any patient with an antibody has to have two red cell units set up so there is no delay if a transfusion is necessary. I would rather have two type O units typed for some antigens, because if the patient with the antibody doesn’t need it, the units are readily available to anyone else.  I use the flexibility of type O blood to be more versatile and to make sure that my patients are getting the freshest possible unit. I have searched for literature that says giving type specific blood is better for patient outcomes but I haven’t found it. If anyone has literature on the topic please send it my way.

This really comes down to what type of setting your blood bank serves. If you are in a medium size community hospital you will need to make these type of decisions to be flexible with your inventory. If you are a large medical center and are going through blood as soon as it gets delivered then you may not have to worry as much. The majority of us do not work for large centers, however, so we must look and analyze how we can best use this precious resource.

 

TommyTransfusion

Tommy Transfusion is the pseudonym of a blood bank supervisor in the midwest.

Blood Management: The Power of “Why”

There are five established questions that should always be embedded in our quest for knowledge and review within the ever-changing evidence base in medicine: what, who, when, how and why. Of these very important and inclusive queries, the final question wields the most power. For it is the why we do, or should do something that truly empowers us. “Why,” by definition, represents the cause, reason, or purpose for action.

Considering the rapid evolution of the evidence base in transfusion medicine and patient blood management, once again, these critical questions should be included in our appraisal. The why remains, however, the most important. Once we grasp that quality, safe, responsible transfusion practice is the purpose, then the what, who, when and how should more easily move forward.

The Joint Commission has begun evaluating patient blood management elements as part of a possible certification for hospitals. The AABB recently published a draft document of patient blood management standards for potential use by its participating facilities. The Society for the Advancement of Blood Management just announced a hospital affiliation program to align principles of blood management with the Society’s mission. All of these organizations are pushing the mission of evidence-based transfusion practice in order to promote patient safety and improve outcomes.

It is our duty as healthcare providers to constantly and consistently evaluate practices, whether they represent procedures, devices, pharmaceuticals; whether they are new or time-honored. Hemovigilance i.e. blood management, must also be included in this ongoing assessment.

Time and time again, the literature is pointing us in the direction of restrictive transfusion practices; avoiding unnecessary transfusion and utilizing blood products as part of our armamentarium when truly life-saving. This concept, thus exudes the ideals of appropriate patient care, best practices and stewardship of community resources. Our cause, our reason, our purpose is clearly to improve patient outcomes and well -being.

Embrace it! Get on board! It is the WHY!

Burns

-Carolyn D. Burns, MD, is the Medical Director of Transfusion Services at Strategic Healthcare Group and Assistant Clinical Professor in the Department of Pathology at the University of Louisville in Louisville, Kentucky. She also blogs for TheBloodyTruth.com.

30 Minutes or Less

How many people have heard of the 30 minute rule for units of returned blood? If you haven’t there is folklore that says once a unit of blood leaves the blood bank it is ok to return it to inventory if they get it back before 30 minutes are up. We even have a place on the documentation that accompanies the unit of blood to write down the time that we can accept a return. It was recommended to us that we get an infrared temperature meter so we could actually take the temperature of units when they are returned. One day I decided to play with my new toy and figure out how long a unit could really be out and still be ok to return. Our policy states a unit can be returned if the temperature is 10 degrees Celsius or colder.

I split my little experiment into two parts. Using an expired unit of blood, I left the unit on the counter and took the temperature every minute for 30 minutes. For the second part, I held an expired unit in my hand (simulating a nurse or transporter carrying the unit) and took the temperature every 2 minutes. In the first experiment the unit of blood reached 10°C in 19 minutes; at 30 minutes I recorded a temperature of 14°C. As expected, holding a unit in my hand sped up the rise in temperature; it took 12 minutes for the unit to reach 10°C. After 30 minutes the same unit was 17°C.  In both experiments I mixed the blood before rolling the unit of blood around the thermometer.

This very informal experiment confirmed my suspicion that the temperature of a unit of blood is environment dependent. Put the unit in a warm room and it will warm up faster than if it were in a cold room. When we dispense units we place the unit in a thin plastic bag; the plastic on the blood units themselves is thin as well. There is no insulation from the unit and our warm hands.

So what do you do with this information? If you have a policy or use the 30 minute rule, I recommend suspending it immediately. There is no way of knowing what happens to that blood once it leaves your blood bank. If you do not have an infrared temperature meter, put it on the capital wish list for 2014. They will save you from taking back blood that is not safe and it will put a finite cut off point for taking units back. Once we started using the meter we found that the majority of blood that comes back is not suitable for reissue and ends up being disposed. While we do waste blood, I feel much better knowing that the blood that we do take back is suitable for transfusion and is ultimately better for the patient.

It is performing little experiments like the one outlines above that keeps us all interested in the laboratory field. What other career can you have a question about something, know how to figure out an experiment to find the answer, and then carry it out to see if you were right or not?  Now the real question I have is: when I order the pizza for lab week what are the chances it gets here in 30 minutes or less?

TommyTransfusion

Tommy Transfusion is the pseudonym of a blood bank supervisor in the midwest.

Why Do Two When One Will Do?

Today I attended a great session on transfusion case studies by Carolyn D. Burns, MD, FASCP, and Phillip J. DeChristopher, MD, PhD, FASCP. The speakers were dynamic, personable, and made learning fun. They presented cases on hematology/oncology, transplant recipients, and HLA antibodies, among others. I won’t go over each case—honestly, there was so much great information I’m afraid I won’t do it justice—but I’d like to share tidbits I found interesting.

-A fact that I had forgotten from my blood banking class oh-so-long-ago: the platelets your body makes live for eight to ten days, an autologous platelet transfusion last four days, and a non-autologous transfusion would last three. If a patient has an immune response to a platelet reaction, those platelet might only live a day.

-Fellows and residents in transfusion medicine don’t actually know how to transfuse a unit of blood product. They aren’t aware of what happens in a blood bank or a transfusion center. Laboratory professionals need to be cognizant of this and be open with information. Use teaching moments when they present themselves.

-Eliminate unnecessary transfusions through dialogue with doctor and pathology. Hence the title of this post: “why do two when one will do?” It’s a mantra for the blood banker to live by.

-Don’t be afraid to question orders. Medical technologists might be the first line of defense, so to speak, and are essential when bringing questionable orders to the attention of pathologists. Don’t be afraid to speak up when your instincts are telling you something is off. Hone your critical thinking skills.

-Blood transfusion is like marriage. It should not be entered upon lightly, wantonly or more often than is absolutely necessary.

-This couldn’t be stressed enough: keep the lines of communication open. Ask the doctor and/or nurse questions about the patient; have a open relationship with your medical director; don’t be afraid to ask questions.

 

 

Bump in the Night

When is the last time you spent the night in your lab on the 3rd shift–a month, year… maybe a decade? How many supervisors/managers know exactly what happens on their off shifts? I bring this up because most hospitals require certain staffing levels even if they only see 15-20 labs from ER a night. If this is the case in your facility, you’ve been provided with an excellent opportunity to empower your employees while “doing more with less.” Those duties that are essential but not time sensitive—such as analyzer maintenance, quality control, and batch testing—are well-suited for off shift employees. All it takes is a bit of creative thinking.

When I first started working in my current position, the blood bank was prototypical. We ran all QC on first shift, performed morning duties, and tried to process as many pre-admission testing (PAT surgery) specimens as we could with inpatient specimens mixed in. Second shift was responsible for PAT tests and routine in-patent specimens.  With productivity measures putting pressure on staffing, I thought about how I could rotate duties to allow one of the three 2nd shift technologists to leave early and only work a half shift. First, I made 1st shift responsible for all PAT testing. Second shift was to pour off the Types and Screens and first shift would do them in the morning. Second, to account for the increased workload created on first shift I made the second shift responsible for tube-testing QC and 3rd shift responsible for Gel testing QC. When things quieted down in the evening one technologist could leave.

This is just one way to look at your daily operations and think what could be done to increase productivity. This rotation of duties required a few things.  First I had to teach the off-shifts how to do the QC. This was not a challenge because they were excited to learn something new. Next I had to assure first shift that the other shifts were able to perform these new duties. This aspect was the most difficult even if it meant making their jobs a little easier! Finally, I needed to monitor the workflow to make sure that this change was effective and helped with productivity, which it did.

Working the occasional off-shift has given me insight into what actually goes on in our lab. It is important as managers/supervisors to know the workflow of your lab 24/7. Working a 2nd or 3rd shift is also an opportunity to connect with staff that for the most part you may only see during a shift change. I would encourage all supervisor/managers to be aware of workflow not just during the 8-12 hours you work but for the entire time your lab processes specimens. Try to spend some time on an off shift and see what really goes bump in the night!

-Matthew Herasuta