Dosing and uses of HLA-matched platelets
Thrombocytopenia
There is no difference in dosing HLA-matched platelets compared to standard platelet dosing. Please see platelet monograph for dosing information.
Other Indications & Uses
HLA-matched platelets are indicated for patients that have thrombocytopenia and have demonstrated CCI values consistent with immune refractory thrombocytopenia on at least two occasions. Although antibodies against HLA Class I antigens are the most common cause of alloimmune refractory thrombocytopenia, antibodies against ABO, or less commonly platelet specific antigens may be involved.
Patients with alloimmune thrombocytopenia due to HLA antibodies include multiparous women, recipients of multiple transfusions (particularly platelet or granulocyte transfusions), and recipients of organ transplants. Neonates may also experience transient thrombocytopenia and leukopenia due to passively acquired maternal HLA antibodies. Neonatal alloimmune thrombocytopenia (NAIT) is not usually as severe when due to HLA antibodies as compared to platelet specific antibodies.
HLA-matching requires typing the patient for HLA Class I antigens. Additional studies, including screening for HLA antibodies and other platelet serology assays may be useful. Alternatively, platelet crossmatching may be performed to screen for platelets that might have improved post transfusion increments.
Strategies for providing platelets for alloimmune thrombocytopenia vary by institution and your blood bank physician should be consulted for assistance.
Pediatric dosage forms and strengths
Thrombocytopenia
There is no difference in dosing HLA-matched platelets compared to standard platelet dosing. Please see platelet monograph for dosing information.
HLA-matched 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
HLA-matched platelets are not indicated in patients that have not demonstrated alloimmune refractoriness. Some institutions attempt to provide HLA-matched platelets to patients waiting for transplants in an effort to reduce HLA sensitization, however this approach is not practical or possible for most institutions.
Cautions
HLA-matched platelets should always be irradiated to prevent TA-GVHD. Ordering HLA-matched platelets 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.
HLA-matching does not guarantee expected platelet transfusion responses and it is not uncommon to see suboptimal platelet increment increases.
Please see platelet monograph for complete safety/caution information.
Pregnancy and lactation
Please see platelet monograph for complete safety/caution 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 HLA-matched platelets
HLA-matching is based on matching the A & B loci of HLA Class I antigens since these represent the predominant HLA antigens present on platelets.
HLA matching is graded into 7 categories based on the number of matches. Grade A matches (4 antigen match) are the best but often are not available. Different institutions have different policies on acceptable HLA-Match grades for transfusion and can be discussed with your institution’s blood bank physician.
Please see platelet monograph for more complete pharmacology information including the formula for calculating the CCI.
Mechanism of action
Please see platelet monograph for mechanism of action.
