DIAGNOSIS
Anti-microbial refractory fungal infection in a patient with severe neutropenia requiring granulocyte transfusion
DISCUSSION
Granulocytes (also known as polymorphonuclear neutrophils [PMNs]) are a specialized blood product with limited indications. The main indication for the use of granulocytes is a life-threatening fungal or bacterial infection that is refractory to anti-microbial treatment. Additionally, the patient's absolute neutrophil count needs to be below 500/µL in the peripheral blood [1]. The most common setting for this situation is in patients with hematologic malignancies.
Granulocytes are collected from healthy donors by apheresis technologies. The granulocyte layer can be separated out from the plasma, platelet, and red blood cell (RBC) layer during the centrifugation steps of apheresis. Due to the similar specific gravities of the platelets to granulocytes and RBCs to granulocytes, the product is not purely PMNs. A dose of granulocytes typically contains 2/3 of a dose of platelets and enough RBCs (5-30ml) to require crossmatching of the product. PMNs do not have ABO antigens but the RBCs that are in the unit do and could be hemolyzed if the unit is not compatible with the recipient's plasma [2]. In this case, the patient is AB (the universal recipient) so any ABO type would be compatible.
A standard regimen for a patient needing granulocyte therapy is one dose per day on 5 consecutive days. Each dose would need to come from a different donor who is ABO matched and CMV matched to the patient. If the patient is CMV seropositive then it does not matter what the donors CMV status is, but if the patient is CMV seronegative, the donor must also be CMV seronegative. In other blood products, leukoreduction can confer a CMV safe status to all products regardless of the patient's CMV status. Since the white blood cells are the component that is desired in a granulocyte unit, leukoreduction is not possible and the donor's CMV status must be elucidated.
Once collected, the granulocytes have a 24-hour expiration date but ideally should be transfused within 8 hours of collection, so they must be efficiently transported from the collection site to the hospital [2]. Careful planning by the collection service, the hospital blood bank, and the clinical team is required to make sure the product arrives and is transfused in time. The product should be stored at room temperature without agitation to avoid release of the neutrophil granules before administration to the patient. Due to the short expiration date, infection disease testing cannot be completed on the unit before it would need to be transfused. This is a deviation from standard blood bank practices. To mitigate the risk to the patient, the donors who are selected for granulocyte collection are recent apheresis platelet donors. Regular donors have their blood screened for infectious disease approximately every 30 days. This leads to a very low likelihood that the granulocyte units will be positive for infectious diseases. Infectious disease screening on the granulocyte unit is still completed and reported, but the results do not become available until after the transfusion has been completed. The granulocyte unit should be irradiated to prevent transfusion associated graft-vs-host disease. During administration, the unit should be run through a standard blood filter, but not through a leukoreduction filter [2].
The AABB Standards requires that a unit of granulocytes contains at least 1x1010 granulocytes [3]. While this is the standard, this dose is typically believed to be subtherapeutic. An otherwise healthy adult with a severe bacterial infection will produce between 1011 and 1012 granulocytes within 24 hours. For a granulocyte transfusion to be effective, a patient should be receiving roughly this quantity of granulocytes. A healthy donor who is not stimulated with any medications will have a yield of 0.2-0.8x1010 PMNs from an apheresis collection. This is only approximately 2-10% of what an infected adult would need [4]. Therefore, donors must be stimulated if they are to produce an effective dose. Stimulating a donor with corticosteroids (?4 hours before the collection) will lead to yields of approximately 2x1010 PMNs. Using steroids and granulocyte colony-stimulating factor (G-CSF) (300-480 µg subcutaneously given 12 hours before collection) in conjunction can lead to yields of 4-8x1010 PMNs which is significantly closer to what an infected adult would produce naturally [5]. Stimulating healthy donors with corticosteroids and G-CSF is not without risk. Mild muscle, bone, or head pains are commonly reported, though no long-term adverse effects have been reported [6-7].
While studies have been inclusive about the effectiveness of granulocyte therapy compared to controls, using higher dose granulocytes (from G-CSF stimulated donors) compared to low dose granulocytes (unstimulated or steroid only stimulated) appears to have a survival benefit for patients. Therefore, it is recommended that only granulocytes from G-CSF stimulated donors should be used as a therapy [8]. This patient received 3 doses of granulocytes with increases in the ANC of 500/µL seen after each dose however, there was no clear clinical effect seen. The patient was transferred to hospice care per her wishes after the third day of therapy.
REFERENCES
Contributed by Ian M. Harrold, MD and Darrell Triulzi, MD
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