ABO Discrepancies

Question 1

Define ABO grouping discrepancy

Answer 1

• when FWD & RVS groups don’t match
• reported as indeterminate
  *Must be investigated & resolved before issue blood unit

Question 2

Give 3 e.g. of Clerical error

Answer 2

• incorrect collection/labelling
• incorrect labelling
• Incorrect recording

Question 3

Give 4-6 e.g. of Technical error

Answer 3

• Fibrin formation in sample
• mix-up of sample at set up
• Not put in reagents
• not put correct reagent
• COntaminated/expired reagents
• incorrect cell % / centrifugation / rxn temp / reading

Question 4

Resolution for clerical or technical errors

Answer 4

re-test sample, collect new sample

Question 5

Describe cause & resolution for Group I discrepancy (CAUSED => resolved)

Answer 5

• dec Ab production (newborn, immunodeficient) => Not do RVS for newborn
• sample diluted bc more plasma => add more plasma then centrifuge; OR incubate @ RT (/4ºC) for 15-30 min -> centrifuge

Question 6

Describe cause & resolution for Group II discrepancy (CAUSED => resolved)

Answer 6

• ABO subgroups; OR Dec Ag production (leukaemia, lymphoma) => incubate @ RT or 4ºC for 15-30min -> centrifuge
• excess production of soluble AB (in unwashed RBC) = neutralises a-A or a-B = weak FWD rxn => WASH cells then re-test
• B(A) phenotype = weak expression of A Ag => use diff. gping reagent
• Group A w/ gut disease (Acquired B)= can remove acetyl group from GalNAc => use diff. Ab reagent OR dec pH

Question 7

How can an individual have B(A) phenotype?

Answer 7

• produce Hi [ ] of B glycosyltransferase => adds D-Galactose & N-acetyl-D-galactosamine = weak expression of A Ag on RBC surface

Question 8

Differences of Group I, II, III and IV discrepancies

Answer 8

I: weak reacting (1+ / 2+) or missing (0) Ab in the RVS grouping
II: weak reacting (1+ / 2+) or missing (0) Ag in the FWD grouping
III: weak rxn of 1 Ag & 1 Ab in FWD & RVS grouping
IV: bc transfused = mix-field agglutination in FWD OR extra Ab type w/ weak rxn

Question 9

Describe cause & resolution for Group III discrepancy (CAUSED => resolved)

Answer 9

due to protein or plasma abnormalities -> rouleaux (from multiple myeloma, wharton’s jelly) => • microscope for rouleaux • wash cells w/ saline • perform saline replacement (remove plasma & replace w/ saline = dec [protein]

Question 10

Describe cause & resolution for Group IV discrepancy (CAUSED => resolved)

Answer 10

• bc transfused = mix-field agglutination in FWD => check patient history
• bc additional ABO Ab bc recent transfusion => check patient history
• cold reacting alloAb @ RT => Ab screen/ID @ RT OR use Ag neg cells @ RVS grouping
• bc patient makes Ab to dyes => wash cells
• ABO subgroups (A2 indiv. making a-A1 Ab) => issue RBC that’s XM-compatible by IAT
• cisAB indiv. = dec glycosyltransferase production = dec Ag expression = weak FWD rxns & has weak a-B Ab => family studies

Question 11

4 e.g. of cold reacting alloAb @ RT

Answer 11

Anti -M, -N, -P1, Le^a,

Question 12

Resolving ABO discrepancies generally (6)

Answer 12

• Check, retest sample
• Wash pateint cells, retest
• Check history: age; disease; transfusion history
• determine whether discrepancy is in FWD or RVS grouping
• know reagents
• begin testing for sp causes