Dosing and uses of Platelet specific antigen negative platelets (HPA-1a negative platelets)
Alloimmune Thrombocytopenia
There is no difference in dosing platelet specific antigen negative platelets compared to standard platelet dosing. Please see platelet monograph for dosing information.
Other Indications & Uses
Platelet specific antigen negative units are indicated for neonates with neonatal alloimmune thrombocytopenia (NAIT) due to passively acquired antibodies against platelet specific antigens.
Platelet specific antigen negative units are also indicated for patients with alloimmune refractory thrombocytopenia due to antibodies against platelet specific antigens.
Additional studies, including platelet serology assays may be useful. Alternatively, platelet crossmatching may be performed to screen for platelets that might have improved post transfusion increments. The most common platelet specific antibody implicated in alloimmune thrombocytopenia is HPA-1a; however there are other high frequency antigens that antigen negative recipients can form antibodies against leading to alloimmune thrombocytopenia.
Providing platelets for alloimmune thrombocytopenia vary by institution and your blood bank physician should be consulted for assistance.
Pediatric dosage forms and strengths
Alloimmune Thrombocytopenia
There is no difference in dosing platelet specific antigen negative platelets compared to standard platelet dosing. Please see platelet monograph for dosing information.
Platelet specific antigen negative platelets (HPA-1a negative platelets) adverse (side) effects
Frequency not defined
Hemolytic Transfusion Reactions
Febrile Non-Hemolytic Reactions
Allergic Reactions ranging from urticaria to anaphylaxis
Septic Reactions
Transfusion Related Acute Lung Injury (TRALI)
Circulatory Overload
Transfusion Associated Graft Versus Host Disease
Post-transfusion Purpura
Warnings
Contraindications
Platelet antigen specific negative units are not indicated in patients that have not demonstrated alloimmune thrombocytopenia due to a specific platelet antibody.
Cautions
Ordering platelet specific antigen negative units may require a marked time delay of days to weeks or may not even be possible. Consult your blood bank physician and/or hematologist for recommendations in managing bleeding patients with alloimmune thrombocytopenia.
Since NAIT is a transient problem due to passively acquired antibodies, other strategies such as obtaining washed (and irradiated) maternal platelets or increasing the dosage of untested platelets may be attempted. Consultation with your blood bank physician and/or hematologist is advised.
Please see platelet monograph for complete safety/caution information.
Pregnancy and lactation
Please see platelet monograph for pregnancy/lactation information.
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Platelet specific antigen negative platelets (HPA-1a negative platelets)
Platelet specific antibodies against these high frequency antigens have been implicated in NAIT.
Antigen: Phenotypic Frequency
HPA-1a : 98%
HPA-2a: 99%
HPA-3a: 85%
HPA-4a: 99.9%
HPA-5a: 99%
HPA-15a: 80%
NAIT may be caused by antibodies against other lower frequency platelet specific antigens, but these usually can be adequately treated with untested platelets since these antigens are not present on most donors.
Mechanism of action
Please see platelet monograph for mechanism of action.
