Transfusion Medicine I Flashcards Preview

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Flashcards in Transfusion Medicine I Deck (24):
1

What are all transfusion diseases associated with?

Antigen-antibody reactions

2

What test will be positive with transfusion diseases?

All immune hemolytic states are associated with a positive AHG (Coombs’) Test

3

Isoagglutinins

- normally circulate and do not cause disease
- they are expected, “naturally-occurring”

Ex: A/B antibodies

4

Alloantibodies

- Ab against own species but not self

5

What are the most important aspects of blood transfusion?

• Specimen Identification
• Patient Identification

6

What is the Coombs' test?

Detects Ig or complement proteins on red blood cells with visible RBC agglutination used to observe proteins
attached to the RBCs

7

Anti-Human Globulin

AHG is a serum made by purposely immunizing non-
human animals to human Ig and/or complement proteins

8

Indirect Antiglobulin Test

Detects Ig or complement proteins attached to RBCs in vitro. It is positive when IgG from the patients serum attaches to human RBCs which is visualized with the addition of the Coombs' (AHG) reagent

9

What is blood typing?

The determination of the type of blood (A/B/O) and the Rh factor of the blood.

10

What is blood screening?

Test for unexpected clinically significant red blood cells antibodies

The screen is the admixture of patient’s unknown plasma with RBCs of a known phenotype.

11

How is blood type determined?

“Reactivity” is physically visually assessed by agglutination with admix patient’s RBCs with known typing reagents (anti-A, anti-B and anti-D)

12

What is the usual result of a blood screen?

They are usually negative.

13

What must be done with a positive blood screen result?

A positive screen result requires an antibody identification
(for specificity)

14

What is a crossmatch?

Admix patient’s plasma with blood donor’s red blood cells

15

When is a typing and screen done?

When the need for transfusion is remote

Ex: Surgical patients with low risk of bleeding

16

When is a typing and crossmatch done?

Patients with a high likelihood that RBC transfusion will be required

Ex: Actively bleeding patients

17

Direct Antiglobulin Test

Detects Ig or complement attached to RBCs in vivo in situations where RBCs are sensitized while in circulation

18

What are examples of situations where the DAT will be positive?

-􏰀 Immediate (intravascular) hemolytic transfusion reactions
􏰀- Delayed (extravascular) hemolytic transfusion reactions
-􏰀 Hemolytic disease of the fetus / newborn
􏰀- Autoimmune hemolytic anemias

19

Acute Intravascular Hemolysis

IgM’s lead to intravascular hemolysis via the complement activation with RAPID loss of RBCs.

20

What is the 2nd most common cause of death in blood transfusion?

Acute Intravascular Hemolysis - Due to ABO incompatibility with patient or specimen misidentification

21

What are 3 mechanisms where individuals can be exposed to alloantigens that they lack?

􏰀Pregnancy
􏰀Transfusion 􏰀
Transplantation

22

What are lab signs of hemolysis?

• Falling hemoglobin (Hb) and hematocrit (Hct)
• Hyperbilirubinemia
• Low or absent haptoglobin
• Positive DAT

23

Delayed Extravascular Hemolysis

SLOW RBC destruction due to IgG formation against an unexpected alloantigen with extravascular hemolysis (spleen/liver). Complement is usually NOT active.

Future transfusions must honor the alloantibody, by providing RBC’s negative for that antigen.

24

What are hallmarks of extravascular hemolysys?

- Spherocytosis
- Polychromasia

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