Rack position	1	2	3	4	5	6	7	8	9	10	11
Tube identity	Pt. red cells	2-5% Pt. red cell suspension	A	B	D	DC	Pt. plasma tube	A/	B/	I	II
Tube Additions			Anti-A and Pt. cells	Anti- B and Pt. cells	Anti- D and Pt. cells	Rh control and Pt. Cells		Pt. Plasma and A1 cells	Pt. plasma and B cells	Pt. plasma and I cells	Pt. plasma and II cells

RESULTS: (10 points)

Analyze the results below for each sample and interpret the ABO group and Rh and Antibody Screen result. (DC= Rh control, CC = check cells, NT = not tested, = positive agglutination with check cells). Sample 1 is already resulted for you.

Sample	A	B	D	DC	A/	B/	Group Rh	I IS	I 37	I AHG	I CC	II IS	II 37	II AHG	II CC	Screen Interp
1	4+	0	0	0	0	4+	A NEG	1+	0	0		0	0	0		POS
2	4+	4+	3+	0	0	0		0	0	1+	NT	0	0	2+	NT
3	0	0	2+	0	2+	3+		0	0	0		0	0	0
4	0	2+	0	0	3+	0		0	0	0		0	2+	3+	NT
5	0	4+	2+	0	2+	0		0	1+	2+	NT	0	0	0	0
6	4+	3+	0	0	0	0		0	0	2+	NT	0	0	0

MLT 2471 IMMUNOHEMATOLOGY AND SEROLOGY

ANTIBODY SCREENS AND TYPE & SCREENS (T&S, TS) ONLINE

PRINICPLE:

Clinically significant unexpected antibodies against blood group antigens occur in less than 3% of the population. Antibodies occur more frequently in women than in men because of the possibility of sensitization during pregnancy. Multiple antibodies are more commonly seen in patients older than 60 years who have undergone transfusions multiple times. The primary test that is used in antibody screening and detection is the IAT. Careful and complete identification of an unexpected antibody is important in the prevention of transfusion reactions due to the infusion of the incompatible RBCs, as well as in the diagnosis of HDFN. Most clinically significant antibodies can be identified by agglutination in routine procedures using reagent red blood cells of known antigenic constitution. The plasma being screened for unexpected (atypical) antibodies is reacted at various stages with red cells containing known antigens. If the specific antibody is present in the plasma, a positive reaction will occur with the corresponding antigen on the screening cell. This reaction may manifest itself as either agglutination or hemolysis.

INTERPRETATION:

Screening cells are Group O cells that have known antigens present. Cells must be group O, otherwise, if they were A1, B or AB, patients plasma ABO antibodies would agglutinate the cells making it impossible to screen for non-ABO antibodies. The reagent red cells should contain at least one cell with a homozygous expression of each of the major antigens. Tube testing is performed in three consecutive phases using patient plasma and screening cells.

1. Immediate Spin in saline at room temperature

2. 37 C incubation with a potentiator

3. AHG phase after incubated cells are washed with saline

The manufacturers antigram supplied with each screening cell set indicates the presence or absence of specific antigens in each vial. Results should be consistent with the characteristic of the identified antibody, such as optimal reaction temperature.

A positive reaction, at any phase of testing, indicates that the patient has developed an antibody. This antibody may have been developed in response to stimulation by pregnancy or transfusion. The antibody may also be naturally occurring or non-red cell stimulated. The naturally occurring or non-red cell stimulated antibody will usually be IgM.

1. In what phase(s) did the reaction occur?

   1. IgM usually prefer colder temperatures (Anti-M)

   2. IgG react best at AHG (Rh, Kell, Kidd and Duffy)

   3. Lewis and M antibodies may either be IgM or IgG

2. Did more than one screening cell sample react: If so, did they all react at the same strength? More than one cell could be multiple antibodies. If the reaction strengths are equal and occur at the same phase of testing, suspect a single antibody specificity. Multiple antibodies are suspected when reactions are different strengths and occur at different phases.

3. Is hemolysis or mixed field agglutination present?

   1. Lewis, P and Vel antibodies cause in vitro hemolysis

   2. Mixed field agglutination is associated with Anti-Sda and Lutheran antibodies.

4. Are the cells truly agglutinated, or is rouleaux present?

Check for rouleaux. Patients with Multiple Myeloma or those who have received high molecular weight plasma expanders (dextran) may cause rouleaux.

LIMITATIONS:

Factors influencing antibody screening results:

1. Cell to plasma ratio: prozone, postzone (antigen excess)

2. Temperature: Clinically significant antibodies react at 37C or with AHG

3. Length of incubation:

   1. Too short = decreased opportunity for antibody/antigen attachment

   2. Too long = possibility of dissociation of attached antibody from RBC

4. pH: Optimal pH is 6.8-7.2 (neutral)

The antibody screen will NOT detect antibodies when the titer has dropped below the level of sensitivity for the screening method employed.

The antibody screen will NOT detect antibodies to low frequency antigens that are not present on any of the screening cells.