ABO

Question 1

is a laboratory test used to determine a person’s blood group based on the presence or absence of A and B antigens on red blood cells (RBCs) and the corresponding antibodies in the plasma.

Answer 1

ABO typing

Question 2

two main procedures:

Answer 2

1. Forward Typing (Direct or Front Type, Shift to the Right Typing)
2. Reverse Typing (Back Type, Shift to the Left Typing, Indirect or Serum Typing)

Question 3

FORWARD TYPING
• Also known as:

Answer 3

Front type, shift to the right typing, direct cell typing

Question 4

FT

• Purpose:

Answer 4

Detects ABO antigens (A and B antigens) on the patient’s red blood cells

Question 5

FT

Sample Used:

Answer 5

Patient’s red blood cells (RBCs)

Question 6

FT

Reagents Used:

Answer 6

Commercially prepared anti-sera (Anti-A, Anti-B, sometimes Anti-D for Rh typing)

Question 7

FT

Reaction Principle:

Answer 7

• If a patient’s RBCs have the A antigen, they will agglutinate with Anti-A sera

• If the RBCs have the B antigen, they will agglutinate with Anti-B sera

• If neither antigen is present, no agglutination will occur in both Anti-A and Anti-B sera

• If both antigens are present, agglutination will occur in both

Question 8

RT
• Reagents Used:

Answer 8

Known red cells (A1 cells and B cells)

Question 9

RT

•	Also known as:

Answer 9

Back type, shift to the left typing, indirect or serum typing

Question 10

RT

• Purpose:

Answer 10

Detects ABO antibodies (Anti-A and Anti-B) in the patient’s plasma

Question 11

RT

• Sample Used:

Answer 11

Patient’s plasma or serum

Question 12

RT

Reaction Principle:

Answer 12

• If a patient’s plasma contains Anti-A antibodies, it will agglutinate with A1 cells

• If a patient’s plasma contains Anti-B antibodies, it will agglutinate with B cells

• If no antibodies are present, no agglutination occurs

Question 13

Why Perform Both Forward and Reverse Typing?

Answer 13

• Forward typing alone can identify ABO antigens, but not antibodies.

• Reverse typing confirms the result by checking for corresponding antibodies in plasma.

• The two tests should be consistent with each other to ensure accurate blood typing.

• Discrepancies between forward and reverse typing must be investigated before issuing blood.

Question 14

is the clumping of red blood cells due to_____.

Answer 14

Agglutination

antigen-antibody binding

Question 15

Agglutination

It is graded based on the____ and ______

Answer 15

size of the agglutinates and the clarity of the background

Question 16

4+

Answer 16

Red cell button is a solid agglutinate with a clear background

Question 17

3+

Answer 17

Several large agglutinates with a clear background

Question 18

2+

Answer 18

Many medium-sized agglutinates with a clear background

Question 19

1+

Answer 19

Medium- and small-sized agglutinates with a turbid (cloudy) background due to many free RBCs

Question 20

0

Answer 20

(Negative) No visible agglutination; red cells flow freely when resuspended

Question 21

require further investigation (e.g., weak subgroups, transfusion history).

Answer 21

Weak or mixed-field reactions

Question 22

is the clumping of red blood cells (RBCs) caused by the interaction of antigens on the RBC membrane with specific antibodies.

Answer 22

Hemagglutination

Question 23

This reaction is crucial in blood typing, crossmatching, and detecting antibodies in serological testing.

The degree of agglutination provides information on the strength of antigen-antibody interactions.

Answer 23

Hemagglutination

Question 24

Why is Grading Important?

Answer 24

• Standardization: Ensures uniform interpretation across different laboratories.

• Clinical Relevance: Helps in detecting weak antibodies or weak antigen expressions.

• Troubleshooting: Identifies issues like mixed-field reactions or rouleaux formation.

Question 25

is always considered a positive reaction, as it indicates the destruction of RBCs by antibodies (e.g., in hemolytic transfusion reactions).

Answer 25

• Hemolysis (H)

Question 26

suggest weak reactions, requiring further evaluation.

Answer 26

• Lower grades (W+ and 1+)

Question 27

• indicate strong antigen-antibody reactions.

Answer 27

Higher grades (3+ and 4+)

Question 28

H (Hemolysis) Presence of free hemoglobin in the serum (RBC lysis)

Answer 28

10

Question 29

4+ One solid aggregate (complete agglutination, no free cells)

Answer 29

10

Question 30

3+ Several medium to large aggregates with no free cells

Answer 30

8

Question 31

2+ Many small to medium aggregates, clear background

Answer 31

5

Question 32

1+ Many small aggregates, turbid background

Answer 32

3 + or W+ (Weak Positive) Few small aggregates, mostly unagglutinated cells

Question 33

+m or +m (Microscopic Agglutination) Aggregates only visible under a microscope

Answer 33

1

Question 34

0 (Negative) No visible aggregates, all cells remain unagglutinated

Answer 34

0

Question 35

Red cells appear as stacks of coins, a nonspecific aggregation Not a true agglutination; disappears upon adding saline

Answer 35

R (Rouleaux Formation)

Question 36

Presence of two cell populations, one agglutinated and one free May occur in recent transfusions, chimerism, or weak subgroups

Answer 36

mf (Mixed-Field Agglutination)

Question 37

In blood banking,______ is considered a strong positive reaction because it indicates complement activation and RBC destruction.

Answer 37

hemolysis

Question 38

How to Differentiate in the Lab? Agglutination vs Hemolysis

Answer 38

• Perform a saline wash or saline replacement test: Rouleaux will disperse in saline, while true agglutination remains. • Microscopic examination: Rouleaux appears as stacks of coins, whereas agglutination looks like clumps of irregularly shaped cells.

Question 39

Why Wash RBCs?

Answer 39

• To remove plasma proteins, fibrin, and interfering substances that can cause false reactions. • To eliminate substances like fibrin strands, rouleaux-inducing proteins, and hemolysis-inducing contaminants.

Question 40

How to Wash RBCs?

Answer 40

• Add normal saline (NSS) to the pRBCs. • Mix gently by inverting the tube. • Centrifuge for 3 minutes at 1000-2000g. • Discard the supernatant carefully without disturbing the cell button. • Repeat the process for a total of 3 washes.

Question 41

Why is the Tube Method More Accurate? The tube method provides better sensitivity and specificity than the slide method because:

Answer 41

• It allows better mixing of reagents. • It uses centrifugation, which enhances weak reactions. • It reduces false-negative results that may occur in slide testing.