MLS 2304 Unit 3 Chapter 23: Immune Hemolysis, DAT Patterns, and Differential Diagnosis

What are the two main categories of red blood cell (RBC) destruction?

Nonimmune and Immune

What factors can cause nonimmune RBC destruction?

Mechanical shear, infection, heat, or chemical injury

What is the role of antibodies in immune hemolysis?

Antibodies mark RBCs for removal or lysis

What are the three types of immune hemolysis?

Autoimmune, alloimmune, and drug-associated

What does an antibody against patient RBC antigens indicate?

Autoimmune hemolysis

What does an antibody against nonself RBC antigens indicate?

Alloimmune hemolysis

What is the significance of drug-dependent antibodies?

They can indicate drug-associated hemolysis

How does immunoglobulin G (IgG) influence RBC removal?

IgG can lead to splenic macrophage removal and complement activation

What is the structure of immunoglobulin M (IgM)?

IgM is a pentamer

What is the role of complement component 3 (C3) in hemolysis?

C3 can mediate opsonization or direct lysis of RBCs

What is the direct antiglobulin test (DAT) used for?

To detect IgG and/or complement bound to patient RBCs

What does a positive DAT indicate?

The presence of IgG or C3 on RBCs, suggesting hemolysis

What can a negative DAT result imply?

It does not exclude immune hemolysis

What is warm autoimmune hemolytic anemia (WAIHA)?

A condition where IgG reacts near 37°C, leading to RBC destruction

What distinguishes hereditary spherocytosis from warm autoimmune hemolysis?

Hereditary spherocytosis is inherited, while WAIHA involves IgG coating

What is cold agglutinin disease (CAD)?

A condition where cold-reactive IgM clumps RBCs and activates complement

What is the significance of thermal amplitude in CAD?

It indicates the warmest temperature at which the antibody reacts

What clinical findings are associated with warm autoimmune hemolysis?

Spherocytes and often polychromasia in peripheral blood film

What is the mechanism of macrophage removal in immune hemolysis?

Antibody coating leads to partial membrane removal and loss of deformability

What does C3b coating on RBCs facilitate?

Macrophage clearance of RBCs

What happens during intravascular hemolysis?

RBC lysis occurs within circulation

What is the role of spherocytes in immune hemolysis?

They indicate membrane loss but do not establish immune hemolysis

What factors should be considered when interpreting DAT results?

Hemolysis evidence, transfusion history, and medication history

What is the relationship between spherocytes and hereditary spherocytosis?

Both conditions show spherocytes but have different underlying causes

What laboratory findings support the diagnosis of cold agglutinin disease?

Agglutinated RBCs and C3d detection on DAT

What is the clinical significance of reticulocyte counts in hemolysis?

Increased reticulocytes indicate marrow response to hemolysis

What is the primary function of a Complete Blood Count (CBC)?

To evaluate overall health and detect a variety of disorders, including anemia and infection.

What can cause falsely low RBC counts in a CBC?

Agglutinated RBCs may register as one event, leading to an inaccurate count.

What is MCV in the context of a CBC?

Mean Corpuscular Volume, which measures the average volume of a red blood cell.

What does a high MCHC indicate?

Mean Corpuscular Hemoglobin Concentration, which may appear high due to agglutination.

What condition is associated with cold-binding IgG?

Paroxysmal Cold Hemoglobinuria (PCH).

What is the significance of the Donath-Landsteiner test?

It confirms the presence of a biphasic hemolysin in PCH.

What are the four autoimmune patterns of Autoimmune Hemolytic Anemia (AIHA)?

Warm, Cold, PCH, and Mixed.

What is the primary antibody involved in Warm Autoimmune Hemolysis?

Warm-reactive IgG.

What characterizes Cold Agglutinin Disease?

Cold-reactive IgM that activates complement, leading to agglutination.

What does a positive Direct Antiglobulin Test (DAT) indicate?

It suggests the presence of antibodies bound to RBCs, indicating hemolysis.

What is the primary mechanism of hemolysis in transfusion reactions?

Complement-mediated intravascular lysis.

What is the role of maternal IgG in Hemolytic Disease of the Fetus and Newborn (HDFN)?

Maternal IgG targets fetal RBC antigens, leading to hemolysis.

What are the two types of transfusion reactions?

Acute and Delayed transfusion reactions.

What is the difference between drug-dependent and drug-independent RBC autoantibodies?

Drug-dependent requires the drug for antibody binding; drug-independent occurs without the drug.

What laboratory findings confirm hemolysis?

Increased reticulocytes, LDH, bilirubin, and decreased haptoglobin.

What does a low reticulocyte response indicate?

It may suggest ineffective production of RBCs or peripheral destruction.

What is the significance of morphology in blood films?

It helps identify the type of anemia and underlying causes.

What does increased LDH and bilirubin with low reticulocytes suggest?

Ineffective production of red blood cells.

What is the first step in evaluating anemia?

Assess the reticulocyte response.

What is the role of targeted testing in hemolysis diagnosis?

To confirm hemolysis and identify specific causes.

What does a positive DAT alone not establish?

It does not prove hemolysis; further context is needed.

What are the key markers to assess in a patient with suspected hemolysis?

Reticulocytes, LDH, bilirubin, haptoglobin, and blood film morphology.

What does the presence of spherocytes in a blood film indicate?

It may suggest warm autoimmune hemolysis or hereditary spherocytosis.

What is the importance of the reticulocyte response in diagnosing anemia?

It helps determine whether the bone marrow is responding appropriately to anemia.

What does the presence of schistocytes in a blood film suggest?

It may indicate microangiopathic hemolytic anemia.

What is the clinical significance of a high MCV?

It may indicate macrocytic anemia, often due to vitamin B12 or folate deficiency.

What does the term 'extravascular hemolysis' refer to?

Destruction of red blood cells primarily in the spleen or liver.