Cold Auto Antibodies Flashcards
Where are normal cold Autoantibodies found
what are there specificities
thermal range
-present in all normal human sera
-naturally occurring
-specificities include Anti I, Anti H and Anti IH
-low conc in serum with a thermal range of 4-22C
-can be detected with ABO anomaly or if the instrument cant detect
-AutoAB can be masked by AB in a group O pt
-the difference is the thermal range
What does clinically insignificant mean
-not associated with HDFN
-doenst shorten the survival of transfused red cells
3 groups of pathological cold agglutinins
1) Primary or Idiopathic Cold Agglutinin Syndrome (Primary CAS)
2) Cold Agglutinin Syndrome secondary to infection (Secondary CAS)
3) Paroxysmal Cold Hemoglobinuria (PCH)
What is Pathological Primary CAS
-HA from cold autoAB that reacts at 4, RT and 30 - WIDE THERMAL RANGE
-idiopathic can be SEASONAL , in winter pt can start having signs of anemia
-high titre >1000 at 4C
-IgM activates complement
-mostly caused by Anti I
What is Pathological Primary CAS
Acrocyanosis (Raynaud’s Phenomenon):
-cold extremities
-AB agglutinates red cells in capillaries causing hemolysis
-in the cold , a persons exposed skin temperature can fall down to 28C which activates the cold AutoAB. The activation causes agglutination and fixes complement as RBCs are flowing through the capillaries
-when your temp returns back to 37 the AutoAB elutes off the RBC
-hemolysis occurs because complement was activated
-hemoglobinuria occurs from intravascular hemolysis
-Chronic Mild Anemia doesnt need transfusion of packed cells
-mostly in older people and is associated with Lymphoproliferative disorders
What happens if there are complications in surgery
-it can induce hypothermia
-warm donor blood with blood warmer during transfusion
-use prewarm techniques for crossmatching
-a cold agglutinin screen can be requested and results can be seen at RT and IS
-usually always Auto Anti I , whereas the allo Anti I is not as common
how do you insure there are accurate results for CAS pts
-Spontaneous autogglutination means that the pt samples must be maintained and seperated at 37 for accurate titre and thermal amplitude studies
-Samples for DAT testing must be done in an EDTA tube to inhibit in vitro attachment of complement to cells after collection
how is the testing done to screening for cold AutoAB
-test the ability of the pt serum to agglutinate at 20C and 4C
-test with diluted serum with Group O adult and cord cells at RT or 4 c
- positive = titre?
What is Cold Agglutinin Syndrome secondary to infection
-transient
-happens secondary to Upper resp infection Cold autoAB is IgM
-Auto Anti I found in pt with Mycoplasma pneumoniae
-rapid hemolysis
-pts have pallor and jaundiced
Anti i is seen with IM
-low titre
-IgM with narrow thermal range
-Auto anti i = lymphoproliferative disease and CAD
What is Paroxysmal Cold hemoglobinuria (PCH)
-found in kids after a viral illness like measles, mumps, chicken px
-Intravascular HA
-caused by Donath-Landsteiner Antibody
-Biphasic Hemolysin
-D-L antibody is an IgG Auto-Anti-P (Auto hemolysin - destruction of RBC because of cold IgG AutoAB)
-Auto hemolysin binds to pts red cells at lower temps and fixes complement
-hemolysis will occur when red cells return to body core temps and the sensitized cells undergo intravascular hemolysis
-Anti P attaches to red cells at cool temperatures and activates in warmer temps
What is the Donath-Landsteiner test needed for
- confirmation of PCH
-D-L AB binds to red cells and complement at low temps
-when temps return to 37 complement mediated intravascular hemolysis occurs
-in this test blood will be incubated at 4 and 37 since Auto Anti P binds at 4 and causes hemolysis at 37C
What will a cold AIHA show you on a pbs
Decreased RBC
Increased MCV
Rule of 3 violation
Very increased MCH
Very increased MCHC
PBS: agglutination present
What will a warm AIHA show you on a PBS
Normal MCV
Rule of 3 acceptable
Very increased MCHC
PBS: spherocytes, increased polychromasia
What type of sample should be taken for testing for Autoantibody
- EDTA
-put in 37 ASAP
-EDTA is anticomplementary in that complement will not bind in vitro and at 37 it will prevent autoagglutination
-at 37 separate plasma from cells and wash cells with warm saline to be used in further testing
Investigating and Detecting an Autoantibody
- you will know that you have an autoantibody because youll see an anomaly only in Group A, B and AB pts
-positive AB screen in IAT method - in MTS youll see a positive or MF
-do an immediate spin XM or prewarm XM for compatibility
What is done if you suspect a Cold autoAB vs a warm
cold
DAT testing
Set up a cold panel which includes an auto-control and cord cells
COLD AIHA is positive for Complement on RBC
-IgM or complement on Red blood cells
Warm
DAT testing
Set up a panel with an auto-control
-IgG bound to red cells
With a positive DAT what are the reactions noted at RT and IAT
Cold Ab reactions at RT
Auto and DAT Positive
Differential DAT usually indicates only Complement on cells
Proceed with further testing, such as a Cold panel
Warm AB - reactions at IAT
Auto and DAT Positive
Differential DAT usually indicates IgG and/or Complement on cells
Perform Eluate to Identify Autoantibody
Perform Adsorption tests to determine if Allo Antibody is present
How is a Cold Antibody Screen/Cold Panel
-mini cold panel for identifying IgM AB like Anti I , Anti IH or Anti i
-agglutination = presence of normal or pathological allo/auto cold agglutinin
-a cold agglutinin titre is done for testing of significant cold agglutinin
-significance determined by degree of titre and temperature of reactions
how is a cold agglutinin titre completed
-semi quantitative method to measure antibody activity under test conditions
-tells you strength, concentration, and avidity of the AB
-titre can be used to determine the severity of an infection like mycoplasma pneumonia or to differentiate between cold agglutinin because of CAS
how would you cross match pt with cold AB
- Full IAT crossmatch
- Phenotype/antigen negative units, if required
- Auto immune cold antibodies (Cannot find I-negative blood)
- Full IAT crossmatch may still be positive
What is a prewarm crossmatch
-cold AB can mask the presence of a clinically significant AB or make it hard to crossmatch compatible units or interpret a blood group
-prewarm samples at 37 so you eliminate AB that react at colder temperatures
Keep sample warm/separate plasma (37˚C)
Warm all reagents and specimens to 37˚C
Tube IAT testing in 37˚C waterbath:
1) Add 37˚C serum to prewarmed cells
2) Omit the IS and 37˚C reading
3) Wash using prewarmed saline
4) Add AHG and CCC as per SOP
Give Crossmatch Compatible Units
Pathogenic vs benign autoantibodies
Pathogenic
Cold auto-antibodies have a high titre (>1000) and wide thermal amplitude (up to 37˚C)
Benign
Usually have a titre of <64 and only react below 22˚C (4˚C to 22˚C usually benign)
IF it reacts at 31˚C to 37˚C it can be a more severe disease and exhibit sign and symptoms
