Single-Donor Platelets:Arguments for Preferential Use

Paul M. Ness, MD

Transfusion Medicine Division

Johns Hopkins Medical Institutions

TRANSFUSION PRACTICESPlatelets

• Prepared as a byproduct of whole blood collections or by apheresis

• Major use for (1) acute hemorrhage due to thrombocytopenia or (2)prophylaxis during periods of bone marrow aplasia

• Effectiveness limited by alloimmunization during chronic therapy or septic reactions until recently

APHERESIS PLATELETSPOTENTIAL ADVANTAGES

• Reduction in infectious complications

• Reduction in transfusion reactions

• Ease of leukodepletion

• Reduction in transfusion frequency

• Treatment of alloimmunized recipients

• Prevention of alloimmunization

SPTRJOHNS HOPKINS (1987-1990)

• Incidence of 1:4200 transfusions in oncology patients

• Septic reactions were more common with random donor platelet concentrates (RDP)

• Reactions were more common with longer periods of storage

• Source was skin contaminant in 4/7 cases; bacteremic donor in 3/7 cases

Conclusions

• Single donor platelets substantially reduce but do not eliminate SPTR.

• Pretransfusion screening has substantially reduced SPTR, but pathogen redcution will be required to eliminate all SPTR.

• Although current risks of viral infections are miniscule, SDP may be of value to prevent emerging infections

Platelet Transfusion Reactions

• Febrile reactions due to white cells or cytokines produced during storage

• Allergic reactions

• TRALI

Moderate to Severe ReactionsTRAP Study

• Temperature increase > 2 degrees C

• Chills with rigors

• Extensive urticarial eruptions

• Dyspnea

• Cyanosis

• Bronchospasm

• Anaphylaxis

Reduction in Transfusion Reactions

• Premedication is often prescribed but convincing data of efficacy are lacking

• Washing platelets reduces allergic reactions but increments and survival are compromised

• Limiting donor exposure should reduce reactions from contaminating elements

• ULR reduces febrile reactions

Ease of Leukodepletion

• Ongoing debate in the US about universal versus selective leukoreduction

• Current apheresis equipment produces SDP which routinely meet ULR requirements

• Filtration of PC to meet leukoreduction requirements is cumbersome

PLATELET TRANSFUSIONSNorol et al, BLOOD 1998

• Higher platelet dosages increase the transfusion interval from 2 to 4 days

• Higher doses facilitate outpatient therapy.

• Importance of dose is controversial for prevention of bleeding in patients with hematologic malignancies; dose trial to be initiated by TMH Network

PLATELET ALLOIMMUNIZATION

• Most important long term complication of platelet transfusion therapy

• Incidence depends upon patients under study, previous transfusions or pregnancies, and intensity of therapy

• About 1/3 of patients with AML become alloimmunized and refractory to random platelets

PLATELET ALLOIMMUNIZATION

• About 50% of HLA “matched” transfusions are failures

• Alloimmunized recipients remain at risk for hemorrhage when transfusions fail

• Therapy for refractory patients is expensive

SELECTION OF COMPATIBLE DONORS

• Define antibody specificity and avoid incompatible antigens

• HLA matching ( family or volunteer)

• Platelet crossmatching

• Obtain compatible platelets by apheresis

ALLOIMMUNIZATION Therapy Prevention

• HLA matching• Platelet crossmatching• Experimental

therapies

• Leukodepletion• UV irradiation• Reducing donor

exposure with SDP is not effective

APHERESIS PLATELETSPOTENTIAL ADVANTAGES

• Reduction in infectious complications• Reduction in transfusion reactions• Ease of leukodepletion• Reduction in transfusion frequency• Treatment of alloimmunized recipients• Prevention of alloimmunization (UNPROVEN)• Platelet quality

Summary

• We switched to SDP primarily because of the problem with SPTR; even with bacterial detection, we still believe that patient care is enhanced by using SDP.

• Avoiding pooling was a large motivation for the laboratory to move to SDP; with pool and store at the blood center now permissible, we might re-evaluate our position, depending upon the cost.