AIHA Flashcards
Purpose of performing a warm autoadsorption (W.A.R.M.)
- Removes warm autoantibodies
- To ID any clinically significant alloantibodies in patient’s serum
Describe how to perform a warm autoadsorption
- AutoAb removed from patients cells using W.A.R.M. (warm autoantibody removal medium) or ZZAP = DAT neg
- Wash and incubate DAT neg cells at 37ºC to allow warm autoAb to bind
- alloAb will remain in plasma
- Sample is spun = supernatant is removed and step 2 is repeated “X” times depending on titre of autoAb
- Autoadsorbed (clean) plasma can now be tested against screen & panel cells to ID alloAb
T or F: autoadsorption using WARM/ ZZAP can be used for autoAb that have specificity to Kell, MNS and Duffy antigens
FALSE; WARM/ ZZAP destroys Kell, MNS, and Duffy antigens on patient’s cells
- autoAb that have specificity to these antigens will not be removed by treated cells
Why is the Donath-Landsteiner antibody called “biphasic?”
anti-P binds to RBCs at cold temperatures and causes complement-mediated hemolysis after warming to body temperature
Purpose of performing a cold autoadsorption
- Removes cold autoantibodies
- Cold autoAb (IgM) interfere with ABO Rh typing, Ab Scr, XM, and DATs
- To ID any clinically significant alloantibodies in patient’s serum
Describe how to perform a cold autoadsorption
- AutoAb are removed from patient cells = DAT neg
a). prewarm and wash 3-6 times w/ warm saline
b). ZZAP removes IgM autoAb - Incubate DAT neg cells at 4º C with patient plasma
- Sample is spun = supernatant is removed and step 2 is repeated “X” times depending on titre of autoAb
- Autoadsorbed (clean) plasma can now be tested against screen & panel cells to ID alloAb
Discuss PCH: antibody specificity, immunoglobulin class, and ability to bind complement
Paroxysmal (sudden onset) Cold Hemoglobinuria (Hb in urine through IVH)
- Antibody specificity = anti-P
- IgG that reacts in the cold!
- binds complement right to C9 = IVH
What is another name for anti-P ?
Donath-Landsteiner Antibody
PCH etiology
often 2ry to MMRV; often seen in children
Discuss PCH: typical clinical symptoms
intermittent hemolysis with exposure to cold = anemia, fatigue, etc.
Discuss PCH: lab findings
- same as CHD =
- NO SPHEROCYTOSIS
- increased nBRCs
- anemia
- decreased Hb
- decreased haptoglobin
- increased LDH
- increased bilirubin (slow)
Does PCH involve IVH or EVH ?
IVH; anti-P binds complement right to C9
Describe how to do the Donath-Landsteiner Test and its purpose
Purpose: to identify autoanti-P in PCH
- keep collected blood warm, and allow to clot (37C)
- incubate tests with P(+) RBCs at 4C:
a). patient serum = POS hemolysis
b). normal serum = NEG - warm to 37C
- spin and read for hemolysis
hemolysis = anti-P present
no hemolysis = anti-P not present
why can’t we use EDTA to test for PCH ?
always SERUM !
EDTA = false negative as it would get rid of Ca 2+ and Mg 2+ which complement needs
why do we add normal serum in the Donath-Landsteiner test?
To supply complement
- in vivo, patient may have used up all of the complement
Compare/ contrast drug-related autoantibodies vs warm autoantibodies
- both are active at body temp
- methyldopa HA and WAIHA are serologically similar
Drug-related autoAb:
- IVH
- Penicillin = IgG Ab = DAT IgG pos
- Quinidine = DAT C3 pos
- Methyldopa = IgG Ab = DAT IgG+C3 pos
WAIHA:
- EVH
- IgG
- DAT IgG pos +/- C3
How is drug-related AIHA different from delayed hemolytic transfusion reactions ?
- Drug-related AIHA is an acute hemolytic reaction
- Delayed hemolytic is usually due to secondary exposure of an RBC antigen
Discuss drug-related AIHA: follow-up investigation
WIP
Causes of autoimmunity
- malfunctioning T cells
- cross-reactivity
- molecular mimicry
- alteration of self-antigens
- secondary to disease
- inherited tendency
Primary idiopathic autoimmunity
- Ab against own RBCs
- unknown cause
- 60 y/o +
autoimmunity secondary to disease
- viral or bacteriogenic disease
- often 2° to CLL
- WBC problems (ex: B cell lymphoma = can make Ab that’s not quite right, if malignant = makes a whole lot)
three main types of AIHA
- WAIHA = 70%
- cold autoimmune hemolytic anemia
> cold hemagglutinin disease (CHD) = 16%
> paroxysmal cold hemoglobinuria = 1-2% - drug-related hemolytic anemia = 12%
instances when DAT is positive
- patient alloantibodies bind donor cells
- maternal Abs bind fetal cells
- passive antibodies (blood products/IVIg)
- autoantibodies
- antibodies/complement due to drugs
What does a DAT positive mean ?
In vivo binding of immunoglobulins, complement components, or both
if a DAT is positive, what follow-up testing is needed ?
elution > Ab ID
Describe warm autoimmune hemolytic anemia
- often in elderly patients
- primary idiopathic
- secondary
> white cell malignancies (CLL, lymphoma, MDS)
> autoimmune diseases (Lupus, rheumatoid arthritis)
> viral infections (children or adults)
clinical symptoms of WAIHA
- pallor
- weakness
- shortness of breath
- dizziness
- jaundice (EVH)
- fever
- splenomegaly
Hematology results of WAIHA (CBC/ peripheral smear/ serological)
CBC:
- hemoglobin and hematocrit decreased
Peripheral smear:
- nRBC
- polychromasia
- spherocytosis
- HJ bodies (seen in asplenic individuals)
Serological indicators of EVH:
- increased bilirubin
- increase LDH
- deceased haptoglobin
- high RDW
T or F: autoadsorptions cannot be performed if the patient has been transfused in the past three months
TRUE; alloantibodies can be adsorbed/removed by donor cells
cold autoantibodies general characteristics
- IgM
- thermal range = 4°C (<15C; sometimes RT; up to 32C)
- binds complement
Compare harmless vs pathological autoanti-I characteristics
Harmless:
- titre <64
- max. thermal range = RT
- rxn not readily enhanced by albumin
- polyclonal
Pathological:
- titre >1000
- max. thermal range = 30°C
- rxn enhanced by albumin
- monoclonal (one B cell going out of control => making this autoAb)
Causes of cold AIHA
- Primary idiopathic = common in older people
- Secondary to disease:
> Mycoplasma pneumonia = anti-I
> Erythromycin use
> EBV = anti-i
CHD physiological and hematological symptoms
Physiological:
- tingling upon cold exposure = auto anti-I attaches at 30°C = decreased blood flow = lack of O2
- when warmed up = IgM pops off BUT complement stays and works more efficiently
Hematological:
- NO SPHEROCYTOSIS
- increased nBRCs
- anemia
treatment for CHD and PCH
- avoid the cold
- wait for secondary infection to clear
Define acrocyanosis
bluish discoloration of the extremities due to decreased amount of oxygen delivered
Describe a CHD investigation
- ID autoAb
- panel
- AC = pos (at RT)
= cord cells = neg - titration = >1000 titre
- DAT
- polyspecific = pos
- IgG = neg
- C3 = pos
Describe a cold agglutinin titration
- pre-warm plasma
- serial dilution
- test with adult O cells, patient cells, and cord cells at various temps (37°C, RT, 4°C)
- determine titre at 4°C
- use strength of adult vs cord cells to determine identity (anti-I vs anti-i)
Often a cold agglutinin screen is performed before doing a ______. if the patient plasma does not react with O adult cells at 4 degrees when diluted at _____, there is no need for _______ _______
Often a cold agglutinin screen is performed before doing a TITRATION. if the patient plasma does not react with O adult cells at 4 degrees when diluted at 1/40 (harmless), there is no need for SERIAL DILUTIONS.
How to find compatible blood after CHD investigation
- prewarm XM samples
- use autoadsorbed patient plasma
- ensure monospecific anti-IgG used (don’t want to pick up complement binding)
- only EDTA
- transfuse using blood warmer if necessary
Characteristics of Drug-induced HA
- ONLY monospecific DAT IgG = pos
- rarely leads to hemolysis
- more often seen as interference
When are blood products used as drugs?
- RhIg given to Rh pos patients with ITP
- IVIg therapy
> monitor Hb
> drop in Hb (<100g/L); perform DAT, Bili, LD
ITP = immune thrombocytopenia; platelet clotting disorder
Describe methyldopa HA
- positive DAT
anemia
autoAb produced
serologically indistinguishable from WAIHA
> panreacting
> specificity
substance sensitizing cells
treatment = take them off drug
Cause of methyldopa HA
- due to methyldopa; antihypertensive drug used in pregnancy
- autoantibody produced is related to dose and time
Discuss methyldopa HA: clinical symptoms and lab results
Symptoms: anemia
Lab results:
- PANREACTING; serologically indistinguishable from WAIHA
- DAT = pos
- Increased LDH, bilirubin, RDW
- Decreased haptoglobin, hemoglobin
Treatment for methyldopa HA
take them off drug
Describe how Drug-adsorption (penicillin) affects testing
- penicillin binds to RBCs
- drug/RBC complex stimulates immune response
- IgG antibodies attaches to penicillin on RBCs = mono-IgG DAT = pos
What causes Drug-adsorption on RBCs ?
- massive IV doses of penicillin
Lab results for drug adsorption
- DAT = pos; due to IgG; neg for C3d
- AbScr = negative bc screen cells do not have penicillin
- Eluate = neg
What is referred to as the “innocent bystander” reaction ?
- when patient makes antibodies to quinidine (a drug)
- immune/ drug complex attaches to RBCs = complement activation = IVH
Describe how quinidine causes AIHA
- “immune complex”
- patient makes drug Ab (IgM)
- Ab-Ag complex binds; RBC activates complement
- RBC destroyed by complement
- IVH
Immune complex lab results
DAT = pos (for complement only; IgM)
Ab Scr = neg
Eluate = NOT done; even if we did = still neg
Cases when complement is only positive for DAT
- Cold AIHA
- Drug-induced (penicillin)
- Immune complex (quinidine)
Cause of membrane modification AIHA
- Cephalosporins ADSORB to RBC
- Modifies RBC membranes (more sticky)
- NON-SPECIFIC BINDING of complement, IgG, IgM, IgA
Lab results for membrane modification AIHA (cephalosporins)
DAT = pos (IgG and complement)
Ab Scr = neg
Eluate = neg
- bc drug Ab are not represented on screen cells
