Blood banking 16.2: Immune Hemolytic Anemias

What happens in the Membrane Modification Mechanism form of immune hemolytic anemia?

-*NON-IMMUNOLOGIC* (not a true drug-induced IHA) -drugs modify the RBC membrane, making it susceptible to nonspecific adsorption of plasma proteins (IgG, IgM, C') -If adsorbed in the right combination on the RBC, C' can be activated and hemolysis occurs

What are Autoantibodies?

-Ab produced to self Ag on RBC -Most react w/ high incidence Ag & therefore react w/ most donor & reagent cells -May interfere w/ type, screen, and crossmatch procedures

How do you resolve interference from cold autoagglutinins when doing Ab screening and panels?

-Adsorption to remove cold auto-Ab before testing for allo-Ab; -Prewarm cells & serum before testing -Avoid RT centrifugation -Wash w/ saline at 37-45C; -use IgG AHG

What drugs are involved with the drug-adsorption mechanism of drug-induced immune hemolytic anemia?

-Cephalopsporins, -streptomycin, -massive doses of penicillin

How do cold autoagglutinins interfere with ABO/Rh typing?

-Cold autoagglutinins coat the RBC & may cause spontaneous agglutination -they may cause false-pos reactions w/ routine ABO reagents

What are the characteristic lab results in PCH?

-DAT: IgG AHG neg; C3 AHG 3+ or 4+ -IgG Ab (cold/warm): Auto anti-P, biphasic

What are the characteristic lab results of CAS?

-DAT: IgG AHG neg; C3 AHG 3+ or 4+ -IgM Ab: Auto anti-I; Auto anti-IH, Auto anti-i (most common auto anti-I)

What are the lab findings in WAIHA?

-Decreased Hgb, decreased Hct, and decreased haptoglobin -Increased bilirubin & urinary urobilinogen -Ab found: IgG1, IgG3 -sensitized rbc are removed from circulation by phagocytes and destroyed extravascularly by the liver and spleen

Which monoclonal reagent will warm autoantibodies react with most often? 2nd?

-IgG AHG (67%) -C3 AHG (7%)

Why is it important to recognize autoantibodies?

-May explain decreased rbc survival in vivo and offer an explanation for an otherwise unexplained anemia -May be hard to accurately determine ABO/Rh type -May affect the results of the Ab screen, compatibility testing, and reverse ABO typing

In warm autoimmune hemolytic anemia (WAIHA), what are the associated disorders and how does it usually start?

-Onset is usually insidious, precipitated by infection, trauma, surgery, pregnancy, stress -Disorders include Hodgkins, SLE, RA, viral syndromes, ulcerative colitis, benign tumors

With paroxysmal cold hemoglobinuria, what happens to the body? (what are the clinical features of PCH?)

-Patient's RBCs, when they pass through the extremities at cold temperatures, become sensitized and C' binds; -When the body temperature rises to 37C, intravascular hemolysis occurs; -Acute attacks upon exposure to the cold; Rapid hemolysis -Mainly in children (acute); -Secondary to viral infections

What are the lab findings in drug absorption mechanism?

-Pos DAT (IgG AHG) -Occasionally pos DAT (C3 AHG) -*no interference in blood bank testing* -Neg eluate for Ab screen (b/c no drug on screen cells)

What are the lab findings with Immune complex mechanism form of drug-induced immune hemolytic anemia?

-Pos DAT with both IgG and C3 AHG -Neg eluate for Ab screen -No interference in crossmatch

What are the lab findings in membrane modification mechanism?

-Pos DAT, maybe due to IgG and/or C' -neg eluates -No interference in screen or crossmatch

When should you suspect cold autoantibodies?

-Pos autocontrol at IS/RT phase -Pos DAT at IS, w/ polyspecific AHG; differentiate w/ monospecific AHG (monospecific IgG AHG is neg; C3 AHG is pos) -Pos Ab screen at IS -precipitate/clumping sticks to the tubes but disappears at 37C/warming.

When should you suspect warm autoantibodies?

-Pos autocontrol in the AHG phase -Pos DAT in AHG phase; use different AHG reagents to differentiate b/t anti-IgG and anti-C3 -Pos Ab screen in AHG phase

Characteristics of warm autoantibodies?

-React w/ high incidence RBC Ag -May mask allo-Ab that may be present in patients having previous transfusions or pregnancies -May activate C' -Enhanced w/ enzyme techniques -Pos autocontrol in the AHG phase -Pos DAT in AHG phase; use different AHG reagents to differentiate b/t anti-IgG and anti-C3 -Pos Ab screen in AHG phase

How do you ID Ab with CAS?

-Test at < RT (including O cord cells)

What happens in the Immune Complex Mechanism form of drug induced immune hemolytic anemia?

-drug is NOT bound to RBC membrane -drug combines w/ plasma proteins & becomes immunogenic; Ab are produced -drug-Ab complexes indiscriminately bind to RBC & other cells and membranes, and may activate C' leading to hemolysis (*"innocent bystander* *mechanism"*

How do you select blood for WAIHA recipients?

-ensure compatibility w/ any allo-Ab present in recipient's serum -Compatibility w/ auto-Ab is controversial: if auto-Ab shows simple specificity (anti-e), select e neg units but be aware of other Ag on donor cells that may stimulate the production of allo-Ab. If auto-Ab shows broad-specificity, select the least incompatible donor unit

Characteristics of pathologic cold autoantibodies?

-may react at >= 30C (warm) -Titer @ 4C >= 1000 -reaction strongly enhanced w/ albumin -Anti-I -Biphasic, can bind C' -clinically significant -*may be secondary to viral or M. pneumoniae* *infection*

Characteristics of benign (normal) cold autoantibodies?

-react below 20-24C -titer at 4C <= 64 -reaction marginally enhanced w/ albumin -Anti-I -IgM, Can bind C' -Not clinically significant -not associated w/ disease

How do you resolve interference from cold autoagglutinins when doing compatibility testing?

-use prewarmed or adsorbed serum -use IgG AHG

How do you resolve interference from cold autoagglutinins in doing ABO/Rh typing?

-wash the patient's RBC w/ saline at 37-45C before testing, autoadsorption for serum. prevents reattachment in vitro -Prewarming is another technique, but not always reliable as some ABO isoagglutinins are not reactive at 37C; promotes dissociation of Ab from RBC

What are 2 types of AIHA?

1. 16-32% Cold Agglutinin Syndrome (CAS) 2. 0-2% Paroxysmal cold hemoglobinuria (PCH)

What are 3 causes of Immune hemolytic anemias?

1. Alloantibodies 2. Autoantibodies 3. Drug-induced Antibodies

What happens in Drug Absorption Mechanism?

1. Drug binds to proteins on RBC 2. Body produces anti-drug IgG 3. Anti-drug IgG attaches to drug on RBC, C' binds, & cells are destroyed intravascularly.

What are the steps to remove interfering warm autoAb by autoadsorption in order to type & screen, crossmatch, and test for allo-Ab?

1. Elute auto-Ab from patient's RBC by using ZZAP or other method 2. Adsorb patient's serum with these cells 3. Spin and remove serum 4. Test serum for allo-Ab

What are 2 types of CAS?

1. Idiopathic cold AIHA 2. Secondary cold AIHA: transient disease secondary to infection by *M. pneumoniae or EBV*(infect. mono)

What are 3 types of AIHA?

1. Warm reacting (70%) 2. Cold reacting (18%) 3. Drug induced (12%)

What are the 3 types of drug induced immune hemolytic anemias?

1. drug absorption mechanism 2. immune complex mechanism 3. membrane modification mechanism *NO AUTOANTIBODIES INVOLVED*

What are the test reactions with warm autoantibodies?

AHG and/or 37C: -4+ reaction w/ R1R1 and rr RBC -3+ reaction w/ R2r RBC -0 reaction w/ R2R2 RBC

What are drug-induced antibodies?

Ab produced to a drug or drug complex

What are alloantibodies?

Ab produced to foreign Ag on RBC introduced by transfusion or pregnancy

What is a drug that can induce Drug-Induced AIHA?

Aldomet (a methyldopa, treats hypertension) -when taken off aldomet, the AIHA may be present for several years

What is the autoantibody associated with PCH?

Autoanti-P -biphasic -Positive Donath-Landsteiner test

What is cold agglutinin syndrome (CAS) also called?

CHD: cold hemagglutinin disease

What are the drugs involved in drug induced hemolytic anemia caused by RBC membrane modification?

Cephalosporins (mainly cephalothin aka Keflin)

With drug-induced autoimmune hemolytic anemia, what happens to the body?

Decreased hemoglobin, hematocrit, and haptoglobin; Increased bilirubin and urinary urobilinogen (same as warm autoAb)

How do you resolve problems when testing with drug induced AIHA?

Eluate Ab from the RBC before testing.

What are some of the cold antibodies?

M, N, I, P, Lewis

What autoantibodies are seen in drug induced AIHA?

NONE; these are hemolytic anemias induced by certain drugs

Which test distinguishes AIHA from other types of anemia?

Positive Direct antiglobulin test (DAT) using polyspecific and monospecific AHG, followed by antibody identification using normal methods -differentiate b/t monospecific IgG AHG and monospecific C3 AHG

What drugs are involved with the immune complex mechanism of drug-induced immune hemolytic anemia?

Quinidine, phenacetin, and other drugs

What is the definition of autoimmune hemolytic anemia?

RBCs have decreased survival (anemia) because of hemolysis, but specifically hemolysis that occurs because an individual produces antibodies against their own RBC antigens (they attack their own)(self Ag)

In Drug-induced AIHA, the Ab is a true IgG autoAb that preferentially binds to what?

Rh system antigens, particularly e

How do you treat immune complex mechanism?

Stop treatment; quick reversal upon stopping the drug

How do you treat membrane modification mechanism?

Stop treatment; will only limit the condition

What does drug-induced AIHA mimic?

WAIHA (same symptoms, etc) -check the patient's medicinal history

With cold agglutinin syndrome, what happens to the body? (What are the clinical features of CAS)

When the person's body gets cold, the IgM autoantibodies get sensitized, and then as blood travels through the extremities (hands, feet, face), those RBCs agglutinate in the presence of the autoantibodies Complement binds, and intravascular hemolysis occurs It is *mainly chronic (particularly with older adults)* *and rarely severe* -is idiopathic or secondary to M. pneumoniae or EBV

In PCH, how may Ab interfere and how do you resolve it?

With type & screen -use adsorption to resolve

In CAS, A, B, and AB adult cells react strongly with what Ab?

anti-I

What is the most common auto-Ab?

anti-I -I Ag is found on most donor cells

In CAS, O adult cells react strongly with what Ab?

anti-I anti-IH

In CAS, O cord cells react strongly with what Ab?? (newborns)

anti-i

Warm autoantibodies show specificity toward this antibody:

e (small e)

When a DAT is positive in AHG phase, which do you use monospecific or polyspecific?

monospecific

In PCH, how do you ID Ab?

perform a panel

What do you do to prevent interference from CAS with type & screen?

prewarm or adsorption

What is the definition of immune hemolytic anemia?

shortened RBC survival due to Ab

How do you treat drug absorption mechanism?

stop treatment; patient should revert to pre-treatment RBC status

Where can you see problems in testing with drug induced AIHA?

type & screen, crossmatch