title: A newly developed gel centrifugation test for quantification of RBC-bound IgG antibodies and their subclasses IgG1 and IgG3: comparison with flow cytometry.
abstract: BACKGROUND
  Novel gel centrifugation test (GCT) cards were evaluated with respect to their ability to estimate the quantity of IgG on RBCs and the determination of the IgG subclasses IgG1 and IgG3.
  
  
  METHODS
  In 65 patients with a positive DAT, the amount of IgG-gamma-, IgG1, and IgG3 on RBCs was examined by use of GCT cards and flow cytometry (FC) in parallel. The results were correlated with the presence or absence of hemolysis. In addition, D+ RBCs were studied after sensitization with anti-D sera from 22 alloimmunized pregnant women.
  
  
  RESULTS
  The amount of IgG on the RBCs as determined by GCT dilution cards correlated with FC (r=0.70, p < 0.0001). IgG subclass results as determined by GCT IgG subclass cards were confirmed by FC in 14 cases with an anti-IgG-gamma-chain titer > or =300, whereas IgG subclass cards were not suitable in cases with anti-IgG-gamma-chain titers less than 300. In 44 patients with 2+ or 3+ DAT in the GCT and anti-IgG-gamma-chain titer < or =30, no hemolysis was observed, whereas hemolysis occurred in 13 of 14 patients with an anti-IgG-gamma-chain titer > or =300. GCT data obtained by IATs with anti-D sera were concordant with FC results.
  
  
  CONCLUSIONS
  There is a correlation between the amount of RBC-bound IgG and immune hemolysis. The GCT cards that detect the anti-IgG-gamma-chain may be useful to predict hemolysis in patients with a 2+ or 3+ DAT in the GCT. The diagnostic value of GCT cards for IgG subclass testing should be investigated further.
authors.affiliation: Department of Transfusion Medicine, University of Göttingen, Göttingen, Germany. rlynen@med.uni-goettingen.de
authors.forename: Rainer
authors.initials: R
authors.lastname: Lynen
authors.forename: Olaf
authors.initials: O
authors.lastname: Krone
authors.forename: Tobias J
authors.initials: TJ
authors.lastname: Legler
authors.forename: Michael
authors.initials: M
authors.lastname: Köhler
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Mayr
mesh_terms: D000328:Adult; D000744:Anemia, Hemolytic, Autoimmune / Q000097:blood; D001787:Blood Group Incompatibility / Q000097:blood; D002498:Centrifugation; D004899:Erythroblastosis, Fetal / Q000097:blood; D004910:Erythrocyte Membrane / Q000276:immunology*; D005260:Female; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D005782:Gels; D006386:Hemagglutination Tests / Q000295:instrumentation; D006461:Hemolysis; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000145:classification; D007142:Immunoglobulin gamma-Chains / Q000097:blood; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D011250:Pregnancy Complications, Hematologic / Q000097:blood; D011256:Pregnancy Outcome; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D005456:Fluorescent Dyes; D005782:Gels; D007074:Immunoglobulin G; D007142:Immunoglobulin gamma-Chains; D016650:Fluorescein-5-isothiocyanate