Resolving Complex Aby mixtures

Question 1

How might Low & High freq. Aby cause unexplained rxns in Aby ID & how each is solved

Answer 1

Lo: Aby’s to these are rare bc not many ppl become exposed to Ag. Solve: Phenocell C screen + ID panel cells
Hi: Aby to these are rare bc most ppl express Ag (not foreign Ag). Solve: Enz treated cells = Ag neg, phenotype pt

Question 2

How can you distinguish if a person has Anti-G or instead has 2 Aby, anti-C + D?

Answer 2

• Anti-C + D: Anti-D stronger than Anti-C
• Anti-G: reaction to anti-C (D-C+ cells) stronger than anti-D (D+C- cells)

Question 3

What’s the G Ag & link to C & D Ag

Answer 3

• present on Rh blood group i.e. on C & D Ag: C+ &/or D+ = G+
• G neg indiv. (rr/cde) produce anti-G Aby
• Note: Anti-G aby reat w/ C+ & D+ cells on panel

Question 4

Describe why it is important to differentiate anti-D+C and anti-G in the management of HDN (to giving Rh(D)Ig

Answer 4

• bc someone producing anti-G (OR anti-G +C) can receive Rh(D)Ig
• BUT someone producing anti-D + C is not bc already produce/have immune anti-D
• differentiate using G- or D- differnetiation

Question 5

What 4 methods can we use to separate & confirm multiple Aby in Aby ID

Answer 5

• Phenotype Pt RBC w/ known Aby, but can’t perform if recently transmufed <3mths
• Adsorption: remove an Aby & ID remaining Aby
• Antigen modification (enhance or degrade Ag): can ID unbound Aby
  -Neutralisation: incubate plasma w/ soluble Ag in fluid = ID unbound Aby. e.g Le Ag in saliva

Question 6

What is adsoprtion

Answer 6

• removal of Aby from plasma/serum
• by having only 1 Ag on RBC to suspected Aby
• now allows you to ID the remaining Aby in plasma

Question 7

Describe the 2 step Enzyme method (Ag modification)

Answer 7

E.g.
1. Destroy Fyb Ag on cells by enz.
2. Enz.-treated cells mixed w/ plasma & unknown Aby bind to cell
3. Wash the cell => remove Aby
4. ID Aby by IAT

Question 8

a) Whats the calculation to determine the % of population having compatible blood?
b) …having compatible blood in fridge?
c) how many units must be screened if need to compatible units

Answer 8

Using freq. tables to find % of finding Ag neg cells (won’t react w/ allo Aby)
a)1. Convert % to decimal
2. Multiply together (can convert back to %)
b). No. of compatible units in fridge = total # units x % compatible in pop
c). # units required / % compatible in pop = units (will need to round up if in decimals)

Question 9

a) How can you identify high-titre, low avidity “like” Aby (HTLA) &
b) the 3-4 blood groups that have these Aby

Answer 9

a) 1+ rxn to most panel cells w/ neg auto (tubes/cards) & high titres (by dilution)
b) -Chido/Rodgers (Ch/Rg)
- John Milton Hagen
- Knops

Question 10

What separation methods can be done when trying to ID anti- Ch/Rg from Gh/Rg neg person

Answer 10

x Can’t use Enz = Ag destroyed, OR reducing agent = R
/ Neutralising w/ normal plasma: 1:1 ratio of pt + normal Pl in test sample. Cnt sample: pt Pl + Alb
-> then ID using Ch/Rg Ag
= neg test, 1+ cnt = pt has anti-Ch/Rg (remember it got removed)

Question 11

What can’t you use when trying to separate:
a) john Milton hagen (JMH)
b) Knops aby

Answer 11

a) Enzymes & reducing agents = Ag destroyed
b) Enz (weakened Ag) & reducing agents (destroyed)