Clinical information
Diagnostic Utility:
- Fetal/neonatal alloimmune thrombocytopenia (FNAIT) is due to the presence in the maternal serum of alloantibodies directed against specific platelet antigens (antigens known as HPA). Most cases of FNAIT are due to alloimmunization against the HPA-1a antigen, but other specificities may be involved.
- Pregnant women who are immunized with anti-HPA antibodies and have a history of FNAIT in a previous pregnancy are at very high risk of recurrence if incompatibility is present in the current pregnancy.
- In these pregnant women, monitoring the titer of anti-HPA antibodies periodically during pregnancy is recommended to assess the treatment to be followed to prevent severe fetal thrombocytopenia.
Method:
- The titration is performed using the MAIPA technique (Immobilization of platelet antigens with monoclonal antibodies).
- The serum of the immunized pregnant woman is faced, pure and in a series of dilutions ½, ¼, etc., with platelets heterozygous for the corresponding antigen, and we choose the monoclonal antibody that binds to the platelet membrane glycoprotein we are interested in studying (e.g. anti GP IIb-IIIa).
- When titrating anti-HPA-1a antibodies, the result is compared with a reference reagent from the National Institute for Biological Standards and Control (World Health Organization reference serum; Ref. 03/152). In this case, this allows the normalization of results between laboratories, expressing the quantity of antibody in international units/ml.
Results:
- The titration results are expressed indicating up to which dilution of the serum a positive result has been observed. For example, a Titer of 16 indicates that we have observed positive results with dilutions 1/2, 1/4, 1/8, and 1/16, and the result has already been negative with a dilution of 1/32.
- When titrating an anti-HPA-1a antibody, the results are also expressed as follows:
Activity of the sample in relation to the WHO International Standard (NIBSC): 25 IU/ml
Response Time:
21 working days
Specimen information
Sample: serum or plasma
Tubes: one EDTA tube or serum (minimum volume of 1 ml plasma or serum)
Stability: At room temperature or at 4°C: 3 days
Transport instructions: At room temperature or at 4°C
Reasons for rejection: Highly hemolyzed sample
Administrative information
BST Code: 4869
Test Description: Platelet antibody titration
Synonyms: --
Section: Immunohematology
BST Rate: Check the updated rates here.
Profiles:
This test is not included in any profile.
References
Jaegtvik S, Husebekk A, Aune B, Øian P, Dahl LB, Skogen B. Neonatal alloimmune thrombocytopenia due to anti-HPA 1a antibodies; the level of maternal antibodies predicts the severity of thrombocytopenia in the newborn. Br J Obstet Gynecol 2000;107:691-4.