National Reference Laboratory for Specialized 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 differential diagnosis of thrombocytopenia and platelet refractoriness. Testing can be beneficial for women whose prior or current fetus or newborn exhibited thrombocytopenia; this testing can involve an evaluation of maternal/paternal compatibility both serologically and using molecular testing.

Screening can detect anti-HLA or anti-platelet antibodies. Antibody identification allows for selection of the most appropriate blood products. Platelet crossmatching can be performed to select platelet products that may improve transfusion outcomes. In addition, if needed, provision of HPA-1a (PlA1) negative platelets can be coordinated.

Contact Information

National Reference Laboratory for Specialized Testing

Email: NRLST_staff@redcross.org

Phone: (215)451-4205

Fax: (215)351-0179

Services available at each of our reference laboratories may vary. Service requests can be submitted via Connect.

Direct and Indirect Platelet Antibody Testing

Indications

For diagnosis of suspected:

Fetal or Neonatal alloimmune thrombocytopenia (FNAIT)
Post-transfusion purpura (PTP)
Autoimmune thrombocytopenic purpura (AITP)
Platelet refractoriness
Drug-induced thrombocytopenia
Other platelet-related diseases

Description

Screening for anti-platelet antibodies (e.g., detection of IgG antibodies to platelets) is available through multiple American Red Cross reference laboratories. In addition, the several American Red Cross reference laboratories including the American Red Cross National Reference Laboratory for Specialized Testing (NRLST) offer additional testing to investigate and characterize platelet-specific auto- and alloantibodies. These tests are used to aid in the diagnosis of platelet-related conditions, such as:

Fetal and Neonatal alloimmune thrombocytopenia (FNAIT): Thrombocytopenia of the fetus and newborn is the result of placental transfer of maternal antibody from an antigen-negative mother to the platelets of an antigen-positive fetus. The most common cause is anti-HPA-1a antibodies but antibodies to other HPA antigens, HLA or ABO incompatibility.
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 multi-transfused patients including those with hematologic malignancies 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. 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) in which serum or plasma is added to a round-bottom well in which platelets from randomly selected donors or from donors selected based on known HPA or HLA types are immobilized and presence of anti-platelet antibodies are detected using red cells as indicators
Platelet suspension immunofluorescence testing (PSIFT) with platelet donor specimens selected based on known HPA types
Bead-based testing for detection of antibodies directed against GPIIb/IIIa (HPA-1a/1b, HPA-3a/3b, HPA-4a), GPIa/IIa (HPA-5) and GPIV.

Platelet Crossmatching

Indications

Platelet crossmatching using the Solid Phase Red Cell Adherence Assay (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 FNAIT, 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

Solid Phase Red Cell Adherence Assay
Glycoprotein-specific ELISA

For human platelet antigen (HPA) typing by molecular methods, visit our Molecular Testing page.

HPA-specific Antigen Negative Platelets

Indications

In certain clinical situations (FNAIT, PTP), it is necessary to transfuse single donor platelets (SDP) from donors who are negative for the high frequency platelet antigen for which the patient has developed an allo-antibody. The most commonly detected anti-platelet antibody is to the HPA-1a molecule. Platelet donors are tested for HPA-1a and HPA-1a negative platelet products are available. Platelet products from donors predicted to lack other HPA antigens such as HPA-5b may be available upon special request.