Platelet Serology Testing
Platelet Serology Testing
The American Red Cross reference laboratories can provide expert assistance with your most complex serological cases to help ensure positive outcomes for your patients.
Platelet serology testing can aid in diagnosing antibody-mediated thrombocytopenia and in investigating the cause of platelet refractoriness. Once the presence of HLA or platelet antibodies is confirmed, appropriate products can be chosen or platelet crossmatching can be performed to select platelets that may improve transfusion outcomes. In addition, a local or national facility can coordinate provision of HPA-1a (PlA1) negative platelets, or recommend further molecular testing.
Services available at each of our HLA laboratories may vary. Please call the national Platelet Serology Laboratory directly at 215-451-4205, or use the Service Request forms below.
Direct and Indirect Platelet Antibody Testing
Indications
For diagnosis of suspected:
- Neonatal alloimmune thrombocytopenia (NAIT)
- Post-transfusion purpura (PTP)
- Autoimmune thrombocytopenic purpura (AITP)
- Platelet refractoriness
- Drug-induced thrombocytopenia
- Other platelet-related diseases
Description
Preliminary platelet testing (e.g., detection of IgG antibodies to platelets) is available through Red Cross Immunohematology Reference Laboratories (IRLs). In addition, the American Red Cross National Reference Laboratory for Platelet Serology and some IRLs offer a wide variety of expanded laboratory techniques to investigate and characterize platelet-specific auto- and alloantibodies. These tests are used to aid in the diagnosis of platelet-related conditions, such as:
- Neonatal alloimmune thrombocytopenia (NAIT): Thrombocytopenia of the newborn is the result of placental transfer of maternal antibody from an antigen-negative mother to the platelets of an antigen-positive fetus.
- Post-transfusion purpura (PTP): This syndrome is characterized by an abrupt drop in platelet count occurring 7–10 days after transfusion and the presence of platelet-specific antibody(ies).
- Autoimmune thrombocytopenic purpura (AITP): Patients with AITP produce autoantibodies to platelets. In many cases, thrombocytopenia is the only clinical sign.
- Platelet refractoriness: Failure to respond to platelet transfusion is seen most often in leukemic or other multi-transfused patients who are receiving chemotherapy. The usual cause of refractoriness is the production of antibodies to HLA Class I antigens, which are present on the transfused platelets. Antibodies to platelet-specific (HPA) antigens may also be present in some cases.
- Drug-induced thrombocytopenia: Patients become thrombocytopenic during or soon after drug therapy. Heparin, quinine (quinidine) and sulfa drugs are the most frequently studied, but a large number of drugs are known to induce thrombocytopenia.
Test Methods
- Solid Phase Red Cell Adherence Assay (SPRCA)
- Platelet suspension immunofluorescence testing (PSIFT)
- Solid Phase ELISA testing for detection of antibodies directed against GPIIb/IIIa (HPA-1a/1b, HPA-3a/3b, HPA-4a), GPIa/IIa (HPA-5a/5b), GPIbIX, GPIV and HLA Class I
- PF4/polyvinylsulfonate solid phase ELISA testing for detection of antibodies directed against heparin/PF4
- Solid phase ELISA for detection of platelet-associated immunoglobulins (PAIg) against GPIIb/IIIa, GPIb/IX and GPIa/IIa
Platelet Crossmatching
Indications
Platelet crossmatching using the SPRCA technique is widely used to select platelet products for patients who have become refractory. The use of crossmatched platelets may improve transfusion outcome for these individuals on an interim basis until HLA-matched products are available or as continuous transfusion support when the transfusion outcome is favorable. Platelets crossmatched against maternal serum can also be used to support neonates in some cases of NAIT, depending on antibody specificity.
Description
Platelet crossmatch testing detects IgG antibodies to platelet-specific and HLA antigens. A serum or plasma sample from the patient is tested against apheresis platelets. Depending on the antibody, compatible platelets may or may not be readily available. The crossmatching program, in partnership with the HLA matching service, provides transfusion support and medical consultation for refractory patients who are difficult to support by standard methods.
Test Methods
- SPRCA
- Glycoprotein-specific ELISA
For human platelet antigen (HPA) typing by molecular methods, visit our Molecular Testing page.
HPA-1a (PlA1) Negative Platelets
Indications
In certain clinical situations (NAIT, PTP), it is necessary to transfuse single donor platelets (SDP) from donors who are negative for the high frequency platelet antigen HPA-1a.