Poll: Ficin-Treated Red Blood Cells

Read the paper in Lab Medicine or listen to the podcast to learn more about one institution’s ficin protocol.

 

 

Common Thrombotic Microangiopathies

Primary thrombotic microangiopathy (TMA) syndromes encompass diseases that present with thrombosis in small and medium sized blood vessels due to endothelial injury. They are specific disorders that require specific treatment. The initial assessment is focused on confirming that the patient has true microangiopathic hemolytic anemia (MAHA) with or without thrombocytopenia. If MAHA and thrombocytopenia are confirmed it is important to differentiate the primary etiologies, which include:

  1. Thrombotic thrombocytopenic purpura, or TTP, which occurs as a result of severe ADAMTS13 deficiency
  2. Atypical Hemolytic uremic syndrome, or aHUS, which occurs as a result of complement dysregulation
  3. Hemolytic uremic syndrome, or HUS, which occurs as a result of Shiga toxins

TTP results from a severe deficiency of ADAMTS13 (defined as activity <5-10%). ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) is an enzyme that cleaves large von Willebrand multimers. TTP can be hereditary (called Upshaw-Shulman syndrome) but is usually acquired as a result of an inhibitory autoantibody toward ADAMTS13. The decision to treat TTP is usually clinical since ADAMTS13 assays are often not available and may take several days to return a result if sent to a reference laboratory. TTP typically has more systemic manifestations of organ injury compared to other primary TMA syndromes.

Atypical HUS (aHUS) occurs via a complement-mediated pathway most commonly due to gene mutations of complement factors. Patients with antibodies to complement proteins comprise a smaller proportion of aHUS patients. Penetrance of aHUS is low with only a fraction of gene mutation carriers developing the syndrome. In most cases, a complement activation trigger precedes the manifestation of aHUS.

Most cases of HUS are sporadic, resulting from Shiga toxins produced by Shigella dysenteriae and some serotypes of Escherichia coli (especially O157:H7 and O104:H4). Shiga toxins preferentially injure the renal system by binding to CD77 on kidney epithelial and mesangial cells and endothelial cells. This binding causes downstream ribosomal inactivation leading to programmed cell death (apoptosis). The sporadic form of HUS is associated with bloody diarrhea.

The rationale for focusing on the distinction between HUS, aHUS and TTP is due to the different treatment options for each disease. TTP requires urgent plasma exchange to prevent death, while HUS requires treatment of the infection with little benefit from plasma exchange, while aHUS requires treatment with specialized anti-complement medication. Plasma exchange has inherent risks, so determining the cause of TMA is crucial. While no single clinical feature can be used to determine whether TTP, aHUS, or HUS is responsible for a patient’s symptoms, distinguishing factors include:

  1. Patient age – any primary TMA syndromes may occur at any age; however, children typically present with HUS, aHUS, or hereditary TTP, while adults more commonly present with acquired TTP
  2. Kidney injury –the degree of injury is usually less in TTP than in HUS; aHUS affects the arterioles while HUS tends to affect the glomeruli
  3. Systemic symptoms – up to two-thirds of TTP patients will have some neurologic symptoms; overtly bloody diarrhea is more typical for HUS; aHUS primarily involves kidney injury
  4. A previous episode or family history of aHUS – indication for screening for complement dysregulation in aHUS

 

Want to learn more? Check out: George JN, Nester CM. Syndromes of thrombotic microangiopathy. N Engl J Med. 2014;371(7):654-66.

 

Rogers

-Thomas S. Rogers, DO is a third-year resident at the University of Vermont Medical Center, a clinical instructor at the University of Vermont College of Medicine, and the assistant medical director of the Blood Bank and Transfusion Medicine service.

 

Daratumumab and Blood Bank Testing

Daratumumab, also known as Darzalex, DARA, or Dara-T, is a new medication recently approved in the US by the FDA to treat multiple myeloma. Daratumumab is a novel monoclonal antibody that targets CD38, an integral membrane protein expressed on both plasma cells and red blood cells (RBC). So while the CD38 antibodies are busy destroying the malignant myelomatous plasma cells, they will also be binding onto RBCs. Thankfully, the anti-CD38 binding of RBCs has not been shown to cause severe hemolysis. However, it has been shown to result in false-positive screening test results in the blood bank in all media (saline, PEG, LISS).

The daratumumab effect manifests as a warm autoantibody and will pan-react to any testing carried out including indirect (IAT) and direct antiglobulin tests (DAT), antihuman globulin (AHG) testing, and antibody screening and identification panels. Thankfully, ABO/RhD testing is not affected. To summarize (adopted from AABB Bulletin #16-02):

  1. ABO/RhD typing: no issues.
  2. Immediate spin crossmatch: no issues.
  3. Antibody screen: all cells positive.
  4. Antibody identification panel: all cells positive (autocontrol may be positive or negative).
  5. DAT: positive or negative.
  6. AHG crossmatch: positive with all RBC units tested.
  7. Adsorptions: panreactivity cannot be eliminated.

Potential future techniques to resolve interference, such as anti-idiotype antibodies to neutralize anti-CD38 in vitro, are on the horizon. In the meantime however, our institution’s Blood Bank has asked the clinical teams and pharmacy to notify the Blood Bank if a patient is going to receive daratumumab so that a baseline type and screen and RBC antigen phenotype or genotype is performed prior to initiating treatment. Once the patient receives daratumumab dithiothreitol (DTT) is used to eliminate the CD38 antigen from the surface of the reagent RBCs thereby eliminating the antibody screen and panel panreactivity. DTT treatment also destroys antigens in the Kell family. Therefore, unless the patient is known to be Kell-positive by phenotype/genotype, Kell-negative units are provided to patients on daratumumab.

Communication between clinicians, pharmacy and Blood Bank when a patient is receiving daratumumab is paramount to prevent delays in Blood Bank testing and transfusion needs. Protocols to handle Blood Bank specimens from patients receiving daratumumab can help streamline testing and reduce turnaround time for transfusion.

For further reading check out the AABB Bulletin #16-02 issued this year.

 

Rogers

-Thomas S. Rogers, DO is a third-year resident at the University of Vermont Medical Center, a clinical instructor at the University of Vermont College of Medicine, and the assistant medical director of the Blood Bank and Transfusion Medicine service.

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.

Transfusion Associated Graft-Versus-Host Disease

Transfusion-associated graft-versus-host disease (TA-GVHD) is a rare complication that develops 4 to 30 days after the transfusion of cellular blood products (i.e. red blood cells, platelets, granulocytes). It can occur in both immunocompromised and immunocompetent patients, and recognition is often delayed because the nonspecific symptoms are attributed to the patient’s underlying diagnosis. TA-GVHD affects the transfusion recipient’s bone marrow and is nearly universally fatal, making prevention absolutely essential.

TA-GVHD is mediated by viable mature immunocompetent donor lymphocytes against the recipient’s antigen presenting cells. TA-GVHD does not occur after most transfusions because the donor lymphocytes are destroyed by the recipient’s immune system before they can mount a response against the host. However, this protective response does not occur in certain settings. One is profound cell-mediated (T cell) immune deficiency, resulting from congenital, acquired, or iatrogenic causes. Another occurs when there is a specific type of partial Human Leukocyte Antigen (HLA) matching between the donor and recipient. HLA molecules are the primary means of distinction between self and non-self. If the donor HLA phenotype is homozygous and the recipient expresses the same HLA haplotype, it may mask donor lymphocytes from the recipient. The end result is engraftment and proliferation of mature donor T cells in the recipient’s bone marrow.

The donor T cells are then activated by mismatched HLA class I major antigens. This immunologic assault typically manifests clinically with fever and an erythematous, maculopapular rash which often progresses to generalized erythroderma. In addition to skin dysfunction, liver, gastrointestinal tract, and bone marrow symptoms are also common. The main laboratory findings of TA-GVHD include pancytopenia due to hypocellular marrow, abnormal liver function tests, and electrolyte abnormalities induced by diarrhea.

The differential diagnosis of TA-GVHD is broad. A more definitive diagnosis is suggested from skin biopsy which classically reveals vacuolization of the basal layer and a histiocytic infiltrate, and occasionally shows an almost pathognomonic finding — satellite dyskeratosis, which is characterized by single, dyskeratotic cells accompanied by lymphocytes. The definitive diagnosis of TA-GVHD relies in demonstrating that circulating lymphocytes have a different HLA phenotype from recipient APCs, proving that they came from the donor.

As mentioned above, TA-GVHD portends a high mortality rate and is poorly responsive to the available therapies; therefore prevention is of primary importance. Current strategies include gamma irradiation or leukocyte inactivation (i.e. pathogen reduction technology) of the blood products prior to transfusion to disable donor lymphocytes. Some of the more common indications for patients requiring irradiated blood products include those who are immunosuppressed, who have received a hematopoietic cell transplant, who are receiving blood components from a related donor, or who are given HLA-matched platelets. There is also evidence that transfusing older products decreases the risk of TA-GVHD due to the shortened lifespan of T cells within the products. In summary, TA-GVHD can occur in both immunocompetent and immunocompromised recipients, is mediated by donor T lymphocytes, and is almost always fatal.

For further reading, please see the review article by Kopolovic et al. A systematic review of transfusion-associated graft-versus-host disease. Blood. 2015;126(3):406-14.

 

Rogers

-Thomas S. Rogers, DO is a third-year resident at the University of Vermont Medical Center, a clinical instructor at the University of Vermont College of Medicine, and the assistant medical director of the Blood Bank and Transfusion Medicine service.

FDA Halts Blood Donation in Two Florida Counties Due to Zika Virus

From the Washington Post:

“In a notice sent to blood centers and posted on the agency’s website Wednesday evening, the FDA said it is requesting all blood centers in Miami-Dade and Broward counties to ‘cease collecting blood immediately’ until those facilities can test individual units of blood donated in those two counties with a special investigational donor screening test for Zika virus or until the establishments implement the use of an approved or investigational pathogen-inactivation technology.”

 

A Brief Overview of 7-day Platelets

The transfusion community has targeted platelets as the primary culprit in transfusion-associated clinical sepsis and fatal microbial infection. Platelets (PLTs) are associated with a higher risk of sepsis and related fatality than any other transfusable blood component. Concerns over bacterial contamination in PLT concentrates prompted the US Food and Drug Administration (FDA) in 1986 to issue a memorandum limiting the storage time of platelet products to 5 days. Only recently did the FDA issue draft guidance describing bacterial testing to improve the safety and availability of PLTs, and outlined the steps necessary for transfusion services to extend apheresis PLTs to 7 days.

Microbial infections were the 4th leading cause of transfusion-related mortality, accounting for 8% of them between 2010 and 2014. PLT storage at ambient room temperature supports high titer bacterial proliferation. Skin flora are the most common source of contamination, occurring at the time of collection. Despite the introduction of improved pre-collection arm preparation and analytically sensitive culture-based bacterial detection methods, the risk of fatal and non-fatal clinical sepsis has persisted.

Most recently, the 2016 AABB standards stated that PLTs may be stored for 7 days only if: 1) storage containers are cleared or approved by FDA for 7-day PLT storage and 2) labeled with the requirement to test every product stored beyond 5 days with a bacteria detection device cleared by FDA and labeled as a “safety measure.” The Verax PGD test is a rapid, single use, lateral flow immunoassay, and the only rapid, day of transfusion test the FDA has cleared as a “safety measure.” The proprietary test detects surface bacterial antigens, namely lipotechoic acid found on gram positive organisms and lipopolysaccharide found on gram negatives. The PGD test as a “safety measure” is to be used in concert with culture, not replace it.

Verax PGD test

Approximately 2.2 million PLT transfusions are administered yearly in the United States, of which more than 90% consist of apheresis PLTs. If the available data were generalized to the entire US apheresis PLT supply, approximately 650 contaminated apheresis PLTs would be caught with the PGD test, preventing septic transfusion reactions and potential fatalities each year. The FDA approval of this test allows non-culture based testing to extend dating from 5 to 7 days and further closes the safety gap that exists in apheresis PLTs.

 

Rogers

-Thomas S. Rogers, DO is a third-year resident at the University of Vermont Medical Center, a clinical instructor at the University of Vermont College of Medicine, and the assistant medical director of the Blood Bank and Transfusion Medicine service.

The author declares that he has no disclosures.