Hemagglutination
Serological testing includes K, Fya, Fyb, Jka, Jkb, S, s (k, cellano, testing performed if indicated) to assess maternal or paternal RBC phenotype status.
Hemagglutination
Antigen testing for D, C, E, c, and e to assess maternal, paternal, or newborn Rh phenotype status
Genotype Testing
- May help resolve serological discrepancies or challenges
- Results can aid in selecting antigen negative RBC units if recently transfused
- Assess risk for HDFN for couples with a previously affected pregnancy
- Test for rare variants not detected by phenotype testing
Polymerase Chain Reaction/Fluorescence Monitoring
- Assess risk for hemolytic transfusion reactions or alloimmune HDFN by genotyping for common and rare RBC antigens.
- Detects 24 variants associated with 35 RBC antigens and phenotypic variants, in addition to the hemoglobin S variant.
- Only clinical platform for RBC genotype testing currently approved by the U.S. Food and Drug Administration (Wilkinson, 2016).
See Related Tests below for antigen-specific genotyping and phenotyping tests.
Testing is useful in determining allelic variants predicting red blood cell (RBC) antigen phenotypes for patients with recent history of transfusion or with conflicting serological antibody results due to partial, variant, or weak expression antigens. Also useful as an aid in management of hemolytic disease of the fetus and newborn (HDFN).
Disease Overview
Prevalence and/or Incidence
Erythrocyte alloimmunization occurs in up to 58% of sickle cell patients, up to 35% in other transfusion-dependent patients, and in approximately 0.8% of all pregnant women.
Symptoms
Transfusion reactions or HDFN can occur due to alloimmunization:
- Intravascular hemolysis: hemoglobinuria, jaundice, shock
- Extravascular hemolysis: fever and chills
- HDFN: fetal hemolytic anemia, hepatosplenomegaly, jaundice, erythroblastosis, neurological damage, hydrops fetalis
Clinical presentation is variable and dependent upon the specific antibody and recipient factors
Pathophysiology
Extravascular Hemolysis
Removal of antibody-bound RBCs via splenic macrophages
Intravascular Hemolysis
- Rare for non-ABO antibodies
- Donor RBCs are destroyed by the recipient's antibodies while they are still inside blood vessels
- Hemoglobin released into plasma and excreted in urine; bilirubin accumulates in blood
HDN-Mediated Disease
- Caused by antigen-antibody mediated red-cell hemolysis from previously transferred maternal antibodies
- Examples of antibodies associated with HDFN:
- Rh (Ant-D, -C, -c, -E, and -e)
- Kell (Anti-K, -k, -Kpa, -Kpb, -Jsa and -Jsb)
- Duffy (Anti-Fya and -Fyb)
- MNS (Anti-M, -N, -S, -s, and -U)
- Kidd (Anti-Jka and -Jkb)
- Anti-D is the most common cause of HDFN, followed by anti-c, anti-K, and anti-E; anti-Jka and -Jkb is rare cause
- Antibodies cross the placenta and cause immune destruction of RBCs in fetus, leads to hydrops fetalis
Genetics
See Genes and Variants Tested table below
Inheritance
Typically codominant for RBC antigens; autosomal recessive for HbS
Test Interpretation
Sensitivity/Specificity
- Clinical sensitivity and specificity
- >99% for C, c, E, e, K, k, Jka, Jkb, Fya, Fyb, M, N, S, s
- Unknown for Kpa, Kpb, Jsa, Jsb, Lua, Lub, Dia, Dib, Coa, Cob, Doa, Dob, Joa, Hy, LWa, LWb, Sc1, Sc2, U, V, VS, HbS
- Analytical sensitivity and specificity
- >99% for C, c, E, e, K, k, Jka, Jkb, Fya, Fyb, M, N, S, s
- Unknown for Kpa, Kpb, Jsa, Jsb, Lua, Lub, Dia, Dib, Coa, Cob, Doa, Dob, Joa, Hy, LWa, LWb, Sc1, Sc2, U, V, VS, HbS
Results
- Predicted phenotype for each RBC antigen tested will be provided
- If identified, weak alleles will be reported
- Possible variant
- Reported for allele combinations that have not widely been reported in the literature
- Indeterminate
- Abnormal signal intensities may result in inability to predict genotype resulting in indeterminate results for all tested antigens and HbS
Limitations
- Only the variants listed will be interrogated
- Does not test for Rh D, a major cause of HDFN
- Patients who have had allogeneic hematopoietic stem cell transplants may have inconclusive results on this test
- Diagnostic/phenotype prediction errors can occur due to
- Rare variants affecting primer/probe binding
- Molecular events that affect the blood-group antigen expression and phenotypes that are not detected by this assay (ie, certain null phenotypes or other phenotypes with altered expression)
- This assay is not designed to diagnose sickle cell disease
References
-
The Blood Group Antigen FactsBook
Reid ME, Lomas-Francis C, Olsson ML. The Blood Group Antigen FactsBook. 3rd ed. Academic Press; 2012.
-
Blood Groups and Red Cell Antigens, Ch 8
Dean L. Blood Groups and Red Cell Antigens. Chapter 8: The Kell blood group. National Center for Biotechnology Information (US). [Accessed: Jun 2019]
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Avent ND. Large-scale blood group genotyping: clinical implications. Br J Haematol. 2009;144(1):3-13.
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Chou ST, Jackson T, Vege S, et al. High prevalence of red blood cell alloimmunization in sickle cell disease despite transfusion from Rh-matched minority donors. Blood. 2013;122(6):1062-1071.
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Cruz Rd, Mota MA, Conti FM, et al. Prevalence of erythrocyte alloimmunization in polytransfused patients. Einstein (Sao Paulo). 2011;9(2):173-178.
Names for FY (ISBT 008) Blood Group Alleles
Gassner C, Hyland C, Red Cell Immunogenetics and Blood Group Terminology. Names for FY (ISBT 008) blood group alleles, v4.1. International Society of Blood Transfusion. [Accessed: Nov 2019]
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Mitra R, Mishra N, Rath GP. Blood groups systems. Indian J Anaesth. 2014;58(5):524-528.
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Wilkinson DS. Clinical Utility of Genotyping Human Erythrocyte Antigens. Lab Med. 2016;47(3):e28-e31.
Typical Testing Strategy
Phenotype Testing