Exam B Practicum SQ Flashcards
Enzymes are proteins that do what for chemical reactions?
They increase the rate of a chemical reaction
In transfusion medicine is what altered by enzymes?
RBC antigens
What are the two most commonly used enzymes in immunohematology?
Papain and ficin
What are the less commonly used enzymes in immunohematology?
bromelin, pronase, trypsin, and chemotrypsin
Where do destroyed antigens reside after enzymes have done their work?
On the part of the molecule that the enzyme removed from the RBC membrane.
When are enzymes used?
To clarify the reaction of weakly reactive antibodies or antibody that may be present or confirm the presence of an antibody.
What is the one step technique for enzyme treatment?
Enzyme is added as an enhancement to the tube containing test plasma and RBCs. The technique is carried out in IAT phase of testing.
What is the two step technique for enzyme treatment?
Treatment of RBCs with enzyme and washing prior to the addition of patient plasma. Method preferred b/c enzymes any antibodies present may be damaged.
How are untreated RBCs and enzyme treated RBCs tested?
They are tested together at the same time to identify all antibodies that may be present in the test sample.
Why would an MLS use neutralization in blood bank?
Aid in identifying a suspected antibody that does not react with a typical pattern. It is done by combining it with a soluble form of the corresponding antigen.
What does saliva neutralize?
ABO (secretor), and Lewis (secretor for Le^b)
What does hydatid cyst fluid and pigeon egg whites neutralize?
Neutralizes anti-P1 b/c it has P1 antigen in the fluid.
What antigen is neutralized by urine?
Sd^a
What is neutralized by serum?
Chido and Rodgers
What is neutralized by breast milk?
What is neutralized by amniotic fluid?
What antigens are destroyed by sulfhydryl reagents? Reagents such as 2-mercaptoethanol (2-ME), Dithiothreitol (DTT, and 2- aminoethylisothiouronium bromide (AET)
Kell antigens
Kidd antibodies can show ___A____ and are ___B___ by enzymes.
A. dosage / B enhanced
What is the purpose of doing an elution?
Freeing any antibodies that are bound to the membrane of RBCs using an acid.
What techniques can be combined with elution?
DAT to further investigate for possible antibodies. Adsorption to detect weakly reactive antigen such as weak ABO subgroup.
What methods are used to detect cold reactive antibodies or antibodies that have a broad temperature range?
Lansteiner and Miller heat elution
Weiner’s freeze–thaw method
Lui’s freeze–thaw method and sonication
What methods are suited for recovering warm- reactive alloantibodies, or autoantibodies?
Organic solvents such as ether, xylene, methylene chloride, and chloroform. Acids can also be used to recover the same antibodies such as digitonin, citric, or glycine.
What procedures remove antibodies but leave RBCs intact?
Gentle heat, chloroquine, and acid glycine - EDTA methods
What factors can cause an eluate to fail?
Improper technique
Inadequate stroma removal
Insufficient washing of the sensitized red blood cells before eluting the
antibody
Incorrect method of transferring washed red blood cells
Incorrect procedure used during the wash phase
Use of saline to prepare eluates
Adsorption is a technique used to….
Remove an antibody or antibodies from plasma. It is done to remove autoantibodies from a patient’s specimen in order to see if other antibodies are present in plasma.
What is the preferred method to remove autoantibodies?
Autologous adsorption. It cannot be used on patients that have been transfused within 3 months because donor RBCs may also have autoantibodies.
What is the preferred method for removing autoantibodies if a patient has been transfused within 3 months?
Allogenic adsorption. It can be used on patients that have been transfused. It can be paired with elution techniques. To separate mixtures of antibodies for identification.
How are RBCs chosen for alllogenic adsorption?
RBC antigens that stimulate the most clinically significant antibodies are considered.
What is the risk of allogenic adsorption?
Not detecting clinical significant antibodies if a weakly reactive alloantibody is diluted or antibody to a high frequency antigen is absorbed. Autoantibodies are only partially absorbed may mimic the reaction pattern of alloantibodies.
Rabbit erythrocyte stoma can remove…
Cold autoantibodies, anti-B, and antibodies in the P blood group system (anti-P1).
True or false, can plasma from adsorption with rabbit erythrocyte stroma be used for ABO typing?
No
When is rabbit erythrocyte stroma preferably used?
When an autoadsorption cannot be performed because a patient with a cold autoantibody has been recently transfused.
What is the risk with rabbit erythrocyte stroma?
It can complex or decrease the strength and remove other IgM antibodies including clinically significant antibodies.
What does titration do?
Used to measure the strength (concentration) of an antibody.
Describe titration
A serial dilutions are made of the antibody containing plasma and tested against selected red blood cells to determine the highest dilution causing a positive reaction. Result or titer is expressed as the reciprocal of the highest plasma dilution reacting +1.
What is titration score?
A number assigned to each positive reaction in the titration based on the strength of the reaction (+1-+4).
What does titration score tell the blood banker about the antibody?
Sum of these scores reflect the total binding strength of the antigen and antibody molecule (known as titration score or avidity). Its useful for comparing how an antibody reacts to different RBCs or how different antibodies react to the same RBC.
Complete the statement; Two antibodies can have the __A__ titer but __B__ titration scores, demonstrating the same strength but differing avidity.
A = same
B = different
Reliable titration results depend on…
technique
What situations is titration useful?
- Used for determining antibody activity
-Determines potential severity of HDFN in alloimmunized pregnant women
-Useful in identifying antibodies to certain high-incidence antigens
-Can distinguish characteristic high-titer, low-avidity antibody (HTLA) and a weakly reactive antibody with a low titer
What cannot be done in a blood panel if all cells are positive?
No antibodies can be excluded
If the autocontrol or DAT is negative and the patient has been transfused or pregnant then the reactions are likely due to….
alloantibodies! Note: Both combinations of multiple antibodies and a single antibody to a high-incidence antigen may cause this pattern of reactivity.
If the autocontrol or DAT is positive, the patient has not been transfused recent, then the results are likely due to an…
Autoantibody that could be warm reactive, cold reactive or both.
If the autocontrol or DAT is positive and the patient has been transfused recently, the results may indicate either….
an autoantibody or a delayed serological transfusion reaction
False-positive panreactivity may occur with….
rouleaux or antibodies to reagents
What is the typical pattern from a patient that has developed an antibody to a high incidence antigen?
Negative autocontrol or DAT, but almost all screen, panel, and donor RBCs react positively.
What is the best way to confirm the specificity of an antibody?
Testing with rare selected cells that lack the antigen.
What is an alternative to confirming an antibody if no rare selected cells are available?
Testing the patient’s plasma against treated cells may provide clues to the antibody’s identity. Know a patient’s ethnicity can be helpful too!
Warm autoantibodies may cause….
Autoimmune hemolytic anemia. They react with patient’s own RBCs at body temperature.
What is the typical pattern of warm autoantibodies?
- Positive autocontrol
-Positive DAT
-All screen, panel, and donor RBCs react positive
Describe panagglutination
An antibody that causes all cells tested to agglutinate. A panagglutinate can be a warm autoantibody (panagglutinin)
What method is used for a patient that may have an alloantibody and hasn’t been transfused in the last 3 months?
autoadsorption. Adsorb plasma and test for alloantibodies.
Patients with warm autoantibodies seem to have an increased….
sensitivity to alloimmunization compared to other patient populations.
Patient cells can be ________ for antigens of clinical significance.
Phenotyped. The cells may be treated to remove antibody prior to phenotyping if the antiserum requires an IAT phase.
What may not be necessary if the patient has phenotypically matched RBC donor units available?
Allogenic adsorption
What kind of antibodies react at temperatures between 4C and 25C and can be autoantibodies or alloantibodies?
Cold agglutinins
What technique or method differentiates cold agglutinins from other antibodies?
autocontrol or DAT
Why are cold agglutinins a concern?
They create problems in the lab by interfering with ABO typing and mask reactions of more clinically significant antibodies.
What are the most common cold autoantibodies?
autoanti-I (big i)
Cold autoantibodies can be specific to what antigens?
Big i, little i, IT, IH, and Pr
What is a good way to show if cold-reactive autoantibodies are clinically significant?
Antibody titer (serial dilution) and thermal amplitude
If cold autoantibodies are masking significant alloantibodies, how can cold autoantibodies be removed?
autoadsorption using a low temperature or by adsorption with rabbit erythrocyte stroma
List some cold alloantibodies
Anti-M, anti-N, anti-P1, anti-Pk, anti-Lea, anti-leb, and anti-Lua
What are three ways to avoid detecting cold alloantibodies using tube method?
- Eliminate IS phase
- Eliminate microscopic readings
- Testing with anti-IgG instead of polyspecific antihuman globulin.
What is the pre-warm technique?
Used to detect presence of slinically significant antibodies in the presence of cold-reactive antibodies.
What is the risk of the prewarm technique?
Warming the plasma causes a decrease in the reactivity of 40-47% of clinically significant antibodies per research.
What does a lab scientist do in the prewarm technique?
Plasma and cells are warmed separately at 47C prior to testing in an attempt to avoid binding of cold antibodies.
If performing tube technique, warm saline may be used in the wash step of IAT.
Prewarming can avoid detecting cold reactive antibodies it could resolve ….
ABO descrepancies due to cold antibodies
What can the lab scientist do to predict the potential complications of cold agglutinins during cardiac surgery?
thermal amplitude and titers
Cold agglutinins are present and a problem in cardiac surgery. What can the surgeon do to avoid disaster?
Blood or patient’s body temp. kept above temp at which cold antibodies react or a plasma exchange to remove cold agglutinins prior to surgery.
In delayed hemolytic reaction the patient exhibits symptoms of…
hemolysis
Delayed serologic reaction the DAT becomes _____ but does not exhibit symptoms of hemolysis
DAT becomes positive
Blood transfusion induces the formation of autoantibodies without the development of
autoimmune hemolytic anemia
Rouleaux can occur as a result of… two things
- various intravenous injections
- abnormal concentration of serum proteins
How can a medical lab scientist differentiate rouleaux from true agglutination?
saline replacement procedure
Patient antibodies can be can be specific to…
antigens, drugs, or chemicals
Antibodies reacting to reagents may mimic reaction patterns to high frequency antigens except in….
Except in crossmatch with donor RBCs will be negative. Differences can be seen if cells from different manufacturers are tested.
What kind of antibiotics would elicit a reaction from antibodies?
neomycin, chloramphenicol, gentamycin
What sugar could elicit a reaction from a patient’s antibody?
Glucose
What are some dyes that can elicit a reaction from a patient’s antibody?
Acriflavine and yellow #5 (tartrazine
What bacteriostatic / antifungal reagent can elicit a reaction from a patient’s antibody?
Paraben, Themerosal, and sodium azide
What miscellaneous chemicals could elicit an a reaction from a patient’s antibody?
EDTA, citrate, and inosine
If a patient’s antibodies are reacting to antibiotics, dyes, bacteriostatic, or antifungal reagent; what would an MLS do to the specimen?
Wash patient RBCs to remove the offending reagent
If glucose is suspected of causing agglutination, what can an MLS do to the specimen?
add glucose to test medium
True or false, antibodies directed towards HLA are not clinically significant.
False, they are clinically significant in RBC transfusion
Antibodies that react to HLA have been associated with…
febrile and nonhemolytic transfusion reactions and cause platelet refractoriness.
Reports suggest something may be responsible for decreased survival of transfused RBCs. What is that something?
Antibodies directed to HLA
Antibodies to HLA can interfere with _____________________________ of clinically significant antibodies
detection and identification. To fix this use adsorption.
Antibodies to HLA are not easy to….
identify in pretransfusion testing
Antibodies to HLA can be adsorbed using…
pooled human platelets
Adsorption can confirm ______ reactions were due to HLA antibodies and can now ID clinically significant antibodies that may have been masked by HLA antibody reactivity.
nonspecific reactions due to HLA antibodies
What should be given to patients with antibodies that react to HLA in pretransfusion testing?
Crossmatch-compatible blood.
Low-incidence antigens are….
Wra, Kpa, Jsa, Cw, Dia, Goa, SC2, Mia, Lua, Cob, and Ytb
What are the typical reactions of antibodies to low incidence antigens?
-Antibody screen is negative but one donor unit is incompatible if IAT crossmatch is performed
-Cell reacting on the panel that is not explained by the antibody or antibodies identified.
-Patient appears to experience a delayed hemolytic or serologic transfusion reaction but antibody screen is negative.
What methods should be used if a patient has a history of an antibody to a low incidence antigen?
IAT crossmatch even if antibody screen is negative
True or false, crossmatch incompatibility may be seen when the patient’s antibody screen is negative.
True per SQ notes. Why?
-Antibody may be A or B in origin. They won’t react to screening cells that are group O.
-Donor cells may contain low frequency antigen that just by chance was not present in the panel.
-Antibody detection RBC may lack antigen
-Reagent RBCs may be too old so labile antigens on donor cells may be stronger than on the reagent RBC
-Donor cells may have positive DAT or polyagglutinable
-Dosage. Antibodies can be missed if screening cells exhibit heterozygous expressions of antigens or if heterozygous cells are used for exclusion and antigen shows dosage.
Define mix field agglutination
Specimen that contain two separate populations of RBCs may demonstrate mix field agglutination in testing.
What procedures could show mixed field agglutination?
ABO/Rh typing
DAT
Antigen phenotyping
Antibody screening
What is the reason why a mix field agglutination may be observed in DAT?
B/c the patient has delayed hemolytic or serologic transfusion reaction
What two antibodies characteristically produces a mixed field agglutination reaction?
Anti-Sda and anti-Lua
Define polyagglutination
State in which surface membrane of a person’s RBC is altered in a way that exposes carbohydrates (abnormal). The affected RBC reacts with all adult plasma except that of self.
Polyagglutinable cells have a __A___ reaction in an autocontrol, but polyagglutinable donor RBCs have a __B___ reaction if used in a serologic cross match
A = negative
B = positive
Polyagglutinable donor or recipient cell will have a ______ reaction if antigen-typed with a human source antiserum.
Positive reaction
Polyagglutinable cells are often undetected in
routine testing
Polyagglutinable RBCs may be the cause of unexplained
unexplained hemolytic transfusion reaction
What is the resolution with polyagglutinable RBCs?
Plant lectins to differentiate types of polyagglutination
How can a patient have polyagglutinable cells?
acquired or inherited (result in exposure of cryptic autoantigens)
What are the different categories of polyagglutination?
-Passively acquired cryptic autoantigen activation
-VA polyagglutination
-Inherited polyagglutination
-Pretransfusion and Compatibility Testing
How would an MLS proceed to get an informed consent from a patient?
Educate the patient about risks and benefits of transfusion. Inform the patient of any alternatives that may be available to patient.
Where does the responsibility lie in educating a patient?
Ordering physician with the help of nursing or lab staff. (emphasis on physician…)
What is required by blood donation facilities?
Policies in place to govern informed consent process.
Consent may be done at what time?
Time of admission or obtained separately when the need to transfuse is identified.
How does a patient give consent when they are incapacitated or unable to?
From a legal medical next of kin who must also be educated before giving consent.
Who are responsible for ordering blood components for transfusion?
Physician or other authorized health professionals
What is considered when blood components are being ordered?
- Name of physician ordering indicated
-Placed early enough to provide sufficient time to perform complete testing
-Orders should include enough clinical information and patient history
-Must include number and types of components required
-Request can be verbal but (must) should be followed up with a written request.
Where should documentation of blood components be?
Patient’s health record as well as transmitted to transfusion service
What is the minimum number of independent patient identifiers on request for transfusion?
2
What can be independent patient identifiers?
Recipient (patient) first and last names
Unique identification number
Patient’s date of birth
Driver’s license number
Other forms of photographic identification
How can patient identification be done?
Eye readable, machine readable info, or a combination of both
Where are specimens labeled?
Patient bedside
What info should be on a patient specimen?
2 patient identifiers (independent), Date of collection, and the initials of collector.
What are the two outcomes for a specimen that does not meet the criteria?
Rejected (into the trash)
Recollected
What are the components of a type and screen?
ABO, Rh type, Antibody test
True or false, RBCs can be released for transfusion based on historical test results.
False, they cannot be released based on past test results. Typing must be done on a current specimen
ABO typing may be performed at least ____ prior to releasing RBCs for transfusion.
Twice. The first time is ABO/Rh type and the second type is a confirmation on a different specimen.
In the event that a patient’s ABO type cannot be determined, Type ___ RBCs may be issued for transfusion until patient’s ABO type is resolved.
Type O. Rh positive or negative depending on certain criterias such as gender and age.
When testing donors for Rh type, donors who appear Rh(D) negative from initial Rh testing get _______ through the antiglobulin phase to identify any donor with _____
additional Rh(D) testing
weak Rh(D) antigen
Weak D donors get what kind of Rh label?
Rh positive label
Giving a weak Rh(D) positive antigen donor to Rh(D) negative patient could result in…
Formation of an anti-D antibody
How are screening tests done to maximize sensitivity and ensure low levels of RBC antibody can be detected?
1.Screening cells must not be pooled
2.Selected to provide at least one expression of all significant antigens
3.Include IAT phase for IgG antibodies
What is not recommended for routine transfusion antibody screening testing?
Autologous control or DAT test
When are RBC reflex test done?
Result of inconclusive or unexpected results during mandatory testing
What does reflex testing include?
methods to resolve ABO discrepancy and positive antibody screen tests
If required it can also include
patient cell antigen typing
Donor cell antigen typing
What is another term to describe crossmatching?
Compatibility testing. Its done prior to releasing RBCs for transfusion
What is compatibility testing?
Its done to detect any ABO incompatibilies with the assigned RBC product to patient before transfusion. The test includes immediate spin testing, incubation/enhancement, and IAt test phase designed to detect unexpected antibodies.
What is a sign in compatibility testing that the donor and patient blood are not compatible?
agglutination in any phase of testing.
Infants under the age of 4 months rarely produce….
RBC antibodies. Their reverse in ABO Rh typing will have forward reactions no reverse reaction. If there is a reaction it may be antibodies from mother circulating in baby.
Some labs include two things in routine neonatal pretransfusion testing. What are they?
Anti-A,B and DAT
What is the major concern with antibody screen testing for neonates?
Detecting and identifying possible passive maternal RBC antibodies
What kind of RBC type is transfused into neonates when needed?
Type O
What is the minimum days RBC units and pigtails are retained by lab?
7 days after transfusion
What is the critical test in pretransfusion testing?
ABO typing
What is minor ABO incompatibility?
Anti-A and Anti-B present in plasma portion of platelet component that could potentially react with A and B antigens in the patient.
What is the reason why patients can be given ABO identical platelets, ABO major incompatible platelets, or ABO minor/major incompatible platelets?
Platelets have a very short shelf life so they will be given the best option available
Patient A can receive A or O platelet
Patient B can receive Bo or O platelet
Patient O can only receive O
Patient AB can receive any platelet type
Platelet Rh match will be done if possible.
A patient receives a transfusion of platelets. At the 10 minute mark the patient’s platelet count only increased by 40% is this patient considered refractory?
Yes, because the patient’s platelet count only increased by 40% at the 10 minute mark. If the patient’s platelet count increased by 50% then the patient would not be considered refractory.
What is considered evidence of alloimmunization of platelets?
Positive platelet crossmatches and/or positive HLA antibody screen
Administration of fractionated products does not necessitate ____A_______ except for the administration of ___B___
A=Pretransfusion testing
B= RhIg
When is treatment of idiopathic thrombocytopenic purpura (ITP) with RhIg effect?
If the patient is Rh(D) positive. It won’t work on Rh(D) negative patients.
What procedures can be done in tube and microplate testing?
ABO typing and grouping
Rh(D) typing
Antibody screening and identification
Crossmatching
Antigen typing
Direct antiglobulin testing
What are the two stages of agglutination?
Sensitization & Lattice
In solid phase testing what is required to coat the wells of a microplate in crossmatch testing?
RBC stroma to adhere the antibodies to the well
Labs typically use the ____ technique for antiglobulin crossmatch for antibody screens.
IAT technique
What is electronic crossmatch?
A software system that uses logic tables to detect ABO incompatibilities between patient and donor. If there are ABO incompatibility it will not release the blood to the nurse for transfusion.
All LIS systems should be _______ upon implementation and after updates are installed. The _______ validation should challenge the logic tables.
Validation
Validation
Surgical blood order schedules are based on….
what is usually transfused in the majority of patients undergoing a particular surgery in a particular facility.
What metric is used to assess inventory management?
Discard rate and crossmatched to transfused ratio (C:T). Ideally C:T should approach 1.
Old first out. New last out.
In some labs they will give O negs or O positive if it is nearing expiration date to a patient that needs transfusion.
In phototherapy the most effective spectrum of light is…
Blue-green region b/c bilirubin is most effectively reduced at this spectrum.
Transfusion of neonate depends on
degree and rate of hemolysis
Resultant increase in bilirubin level
Note: Not uncommon for two volume exchange transfusion to require 1-2 hours to complete
What is continuous exchange transfusion in newborns?
2 points of venous access. The removal of newborn blood and transfusion occur simultaneously.
What is discontinuous exchange transfusion in newborn?
There is access to only one vessel. A small amount of blood can be first slowly removed and then replaced.
Where is EPO produced in a newborn?
The liver. The switch to kidney doesn’t switch until several months old.
In a newborn where does IgA come from?
From breast milk
Infants can produce what immunoglobulin?
IgM in response to antigens in small amounts
What immunoglobulin reaches sufficient levels at 1 year of age?
IgG
What age should neonates be tested for ABO/Rh type?
4 months because the infant can produce antibodies.
Transfusing 10 - 15 mL of RBCs will increase hemloglobin levels by approx. …
2-3 g/dL. Transfusion of a newborn should be complete within 4 hours.
The standard blood filter range is?
170 - 260 microns
Whats an alternative to RBC transfusion besides phototherapy?
recombinant human erythropoietin (rHuEPO) however it doesn’t work for all infants. If the rHuEPO works then supplemental iron therapy is also administered.
Platelet count for a neonate to maintain daily hemostasis is?
50k / L
Platelet count for a sick premature baby ma require a platelet count of
100k / L to prevent bleeding
Additional units are required to provide support for an infant on ECMO. What are they and quantities?
2 - 3 units of RBCs to prime the circuit
1 unit of FFP,
portion of a unit of single-donor platelets
Whats the risk for infants on ECMO?
Transfusion associated CMV and GVHD
During ECMO what is the target for platelet count and hemoglobin for an infant?
Platelet count -> 80k-150k
Hemoglobin -> 10 - 12 g/dL
Whats the purpose of performing a DAT?
- Screen for clinically unexpected autoimmune phenomena
- Detect early manifestation of immune response to recent transfusion
- Assist in diagnosis of HDFN
If cold hemagglutinins are suspected what should be done to the lavender top?
Keep at 37C while transporting to lab.
If DAT is positive what test should be done next?
Perform an elution
What should be asked in patient history?
- Recent transfusion?
- Administration of drug? There are drugs associated with immune hemolysis
- Hematopoietic progenitor cell or organ transplantation
- Administration of IVIG or IV anti-D
