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1、Compatibility Testing,Ahmad Shihada Silmi Msc,FIBMSIUG,What is compatibility testing?,Also called pretransfusion testingPurpose:To select blood components that will not cause harm to the recipient and will have acceptable survival when transfusedIf properly performed,compatibility tests will confirm
2、 ABO compatibility between the component and the recipient and will detect the most clinically significant unexpected antibodies,Compatibility testing?,There are several components of compatibility testingProper specimen collectionReviewing patient transfusion historyABO,Rh,and antibody testing(scre
3、en/ID)CrossmatchingActual transfusion,Compatibility testing,Can be divided into 3 categories:Preanalytical proceduresSerological testingPostanalytical procedures,Pre-analytical phases,Patient identificationSpecimen collectionReview of patient history,Patient Identification,Must confirm recipients ID
4、 from bracelet ON the patientFull patient name and hospital numberName of physician,http:/,Sample Identification,The sample should also have the full patient name,hospital number,and physicianDate and time of collection,phlebotomists initialsAll of this should be on the request form and the sample,S
5、pecimen Tubes,Pink Top-EDTA,Red Top no additives,Specimen Collection,Collected in tube with EDTA or no additivesIf the venipuncture causes hemolysis,the sample may be rejectedTrue hemolysis in the patient is the result of complement activationSamples are labeled at the bedside(pre-labeling is not re
6、commended)A record of individuals who collect(or test)the specimens should be documented in order to“backtrack”in case of an error,Specimen Collection,If the sample is drawn from an IV line,the IV infusion should be stopped 5-10 minutes prior to blood drawing and the first 10 mL discardedTesting sho
7、uld be performed on samples less than 72 hours or else complement dependent antibodies may be missed(complement can become unstable),Getting the history,Look at recipients records for any prior unexpected antibodiesPrevious transfusion reactions,Serological Testing,3 tests:ABO/RhAntibody detection/i
8、dentificationCrossmatch,ABO/Rh Typing,In the ABO typing,the forward and reverse MUST matchIn the Rh typing,the control must be negativeBoth of these will indicate what type of blood should be given,Antibody screen and/or ID,The antibody screen will detect the presence of any unexpected antibodies in
9、 patient serumIf antibodies are detected,identification should be performed using panel cells(with an autocontrol)IS37(LISS)AHGIf an antibody is present,units negative for the antigen must be given Proceed to the crossmatch,Crossmatching,Purpose:Prevent transfusion reactionsIncrease in vivo survival
10、 of red cellsDouble checks for ABO errorsAnother method of detecting antibodies,Crossmatch,Two types of crossmatchesMajor routinely performed in labsMinor not required by AABB since 1976,History,Major vs Minor Crossmatch,Why is the minor crossmatch unnecessary?Donated units are tested for antibodies
11、Most blood is transfused as packed cells,having little antibodies,Crossmatches,The AABB and FDA develop the standards for blood bankingAccording to the AABB Standards:The crossmatch“shall use methods that demonstrate ABO incompatibility and clinically significant antibodies to red cell antigens and
12、shall include an antiglobulin phase”,Crossmatch,Donor RBCs(washed),Patient serum,No agglutination compatible,Agglutination incompatible,The procedure,Donor cells are taken from segments that are attached to the unit itselfSegments are a sampling of the blood and eliminate having to open the actual u
13、nit,Units of whole blood with segments attached,Procedure,ABO/Rh typing is FIRST performedAntibody Screen is performed next.,Crossmatch Procedure,if antibodies are NOT detected:Only immediate spin(IS)is performed using patient serum and donor blood suspensionThis fulfills the AABB standard for ABO i
14、ncompatibilityThis is an INCOMPLETE CROSSMATCHIf antibodies ARE detected:Antigen negative units found and X-matchedAll phases are tested:IS,37,AHGThis is a COMPLETE CROSSMATCH,Crossmatches,WillVerify donor cell ABO compatibilityDetect most antibodies against donor cellsWill NotGuarantee normal survi
15、val of RBCsPrevent patient from developing an antibodyDetect all antibodiesPrevent delayed transfusion reactionsDetect ABO/Rh errors,Incompatible crossmatches,Additional Information on Types of Compatibility Tests,Manual(IS and IAT)Gel TechnologyElectronic(Computerized)Cross matchRed cell Affinity C
16、olumn Technology(ReACT)Solid Phase Adherence Assays(SPAA),Manual(IS and IAT),IS detect RT reactive antibodies(Auto,Alloantibody,Naturally occuring)IAT detect IgG antibodies(Auto&alloantibody),Antibody,Naturally occuring(Cold agglutinin),Acquired,Autoantibody,Alloantibody,Gel Technology,Patient serum
17、,and 1%of suspended RBCs in LIM are dispensed into the microtube and incubated at 37oC for 15 minutes.The card containing the microtubes is then centrifuged at a controlled speed for 10 minutes.At the start of centrifugation the cells are separated from the serum;then they meet the AHG contained in
18、the microtube.Finally the cells are trapped by the gel(if agglutinated)or pellet to the bottom of the tube.,X Match Phases,clinically insignificant such as anti-M,-N,-Lea,-Leb,and-I.,This phase is usually read only macroscopicallyfor agglutination,This phase is read microscopically for agglutination
19、,added to all negative tests and must produce a positive result,Limitations of Pretransfusion Testing,Hemolytic transfusion reaction,if the patients antibody is too weak to be detected.Standard antibody detection methods such as the indirect antiglobulin test require several 100 antibody molecules p
20、er red cell to produce detectable reactions.A hemolytic transfusion reaction due to patient misidentification.For example,group A red cells(meant for transfusion to a group O recipient)will be compatible in vitro tests with an incorrect specimen drawn from a group A person.,Limitations of Pretransfu
21、sion Testing,Hemolytic transfusion reaction if donor red cells are inadvertently hemolysed before entering the patient,e.g.,red cells hemolysed by an improperly functioning blood warmer or red cells hemolysed by contact with an ice pack in a transport container.Nonhemolytic transfusion reactions suc
22、h as allergic,febrile,and other reactions.Pretransfusion test are meant to detect only red cell antibodies.,Incompatible cross match,ABO incompatibility Recheck patient and blood unit ABO groupClinically Significant AbDAT&IAT,Antibody Detection,IAT,IAT is used to detect clinically significant IgG an
23、tibodies bound to RBCS in vitro.Detection of free Abs in patients serum.Clinically significant IgG Abs cause hemolysis or reduce survival of transfused RBCs,like D,c,E,K,k,JKa,JKb,FYa,FYb,S,s.Unimportant Abs:I,P1,Lea,Leb,M,N.Those Abs are Unimportant due toMostly cold reactive(IgM)Could be neutraliz
24、ed,IAT,is principally used forAb detectionAb investigation(identification)Ab titrationCompatibility testing Phenotyping for some RBCs antigens,Reagent used in IAT,Characteristics of RBCs reagent:Three cell reagent sets,Serocyte I,II,III.RBCs antigens corresponding to important and clinically signifi
25、cant Abs.The reagent cells are suspended in saline and 2%-5%antibiotic.Expired reagent should not be used.An antigram defining phenotype of reagent cell must included with every cell.All reagent should be stored at 1-6oC.,Performance IAT,Most clinically significant Abs react at 37oC,RT and IS are no
26、t required.AHG is usually monospecific IgGNo need for polyspecific AHG.Because Anti C will detect Abs during the incubation phase.Anti C enhance the detection of cold agglutinin such as anti I,anti P that are non significant Abs and not important in transfusion.Delaying transfusion in critical situa
27、tions.,Interpretation Result of IAT,Negative IATOCC Positive:Report IAT negative Positive IAT Perform:Ab identification.Ab titration.,Interpretation Result of IAT,Low titer,and weak reactive Abs are failed to be detected Using commercial reagents include RBCs that express important antigens in doubl
28、e dose,as JK(a+b-),JK Fy and Fy(a+b-),Fy(a+b-)cells.Avoiding use of LISS LISS enhance reactivity of cold reactive Abs causing difficulties in detection clinically significant Abs.Increase amount of serum to increase amount of Abs.,Its not a life threatening situation when an unexpected clinically im
29、portant Abs to an RBCs Ags in a blood unit is not detected,BecauseThe plasma volume is small,and Abs will be diluted in recipient circulationUnlikely to cause significant destruction to recipients RBCs.,Antibody Identification,0.3%-2.8%of the population are Ab makers,they produce clinically signific
30、ant Ab.Pregnancy and transfusion are the common cause of immunization to RBCs Ags.,Serological Properties,Abs of blood groups vary in importance and significance due to serological propertiesTemperature phase 37oC reactive Abs as anti D,c,E,K,k,JKa,JKb,FYa,FYb,S,s.Cold agglutinin as anti Lea,Leb,I,P
31、1,M,N.Inducing HDN and HTR Activation complement.Neutralizing by soluble blood group Ags,Problems Encountered,Autoantibody directed against own cell Ags solutionElution IgG Abs can be dissociated from RBCs membrane Ags by physical or chemical means,some procedures destroy membrane,some leave it inta
32、ct.Supernatant fluid(elute)contain the autoantibodies which can be identified.,Problems Encountered,Combination of auto and alloantibody solutionTreatment with ZZAP(Adsorption)ZZAP effectively removes autoantibodies(digestion)allowing more complete absorption of autoantibodies from patients serum,al
33、lowing detection and identification of alloantibody.Chemically treated allogenic RBCs Treated RBCS with proteolytic enzymes,alter some Ags,Problems Encountered,Weak or non reacted with any or some cell reagent.Variable reaction Variable expression of Ags(P1,Lewis)Ags deteriorate on storage(Duffy,P1,
34、M,Lewis)Abs is reacting with more than one Ag.DDCCee 3+Ddccee 1+,Solution Use double dose of corresponding Ags,(Rh,Kidd,Duffy,MNS)Use new cell reagent,Post-analytical phase,Post-analytical phase,Involves labeling,inspecting,and issuing the blood unitLabeling form includes patients full name,ID numbe
35、r,ABO/Rh of patient and unit,donor#,compatibility results,and tech IDForm is attached to the donor unit and only released for the recipientThe unit is visually inspected for abnormalities,such as bacterial contamination,clots,etc,Bacterial contamination,This unit shows bacterial contamination and sh
36、ould NOT be given to the patientThe plasma in the segments is fine,but the plasma in the unit shows heavy hemolysis from bacteria,Issuing blood,When its time to release a blood product to the nurse or physician,a few“checks”must be doneRequisition formComparing requisition form donor unit tag blood
37、product labelName of persons issuing and picking up bloodDate and time of releaseExpiration date,What if the unit is unused?,Blood can be returned if it is not needed for transfusionUnit closure has to remain unopenedStorage temperature must have remained in the required range(1 to 10C for RBCs)If n
38、ot at correct temp,unit must be returned within 30 minutes of issue,Infusion Device,Blood Warmer,Special Circumstances,Emergency Release,In an emergency(ER or OR),there may not be enough time to test the recipients sampleIn this case,blood is released only when signed by the physician(O negative)The
39、 tag must indicate it is not crossmatchedSegments should be retained for X-matchingEvery detail is documented(names,dates.),Emergency Release,Once the specimen is received,ABO/Rh typing and antibody screening should be performedCrossmatching the segments from the released unit should be testedIn add
40、ition,the lab may crossmatch additional units as a precaution if more blood is neededIf death should occur,testing should be complete enough to show that the death was unrelated to an incompatibility,What can be given in an emergency?,Group O Rh-negative red cells or AB plasmaEmergency releaseWomen
41、below or of childbearing ageOr if in doubtGroup O Rh-positive red cellsUsed as a substitutionMale or elderly females,Massive transfusion,Defined as a transfusion approaching or exceeding the recipients own blood volume(about 5 liters or 10-12 units in an adult male)within 24 hour periodThe original
42、sample no longer represents the patients conditionComplete crossmatch not necessary(if no antibodies were detected originally)Give ABO identical unitsIf antibodies were originally IDs,continue to give antigen negative units,Appropriate units to give,ABO compatible should always be given first,Group
43、O individuals are“universal donors”,they can donate to any blood group because they have no A or B antigens Group AB individuals are“universal recipients”,they can receive blood from any group because they do not have A or B antibodies,Red blood cell compatibility table,Plasma compatibility table,O,
44、B,A,AB,AB,B,A,O,Donor,Recipient,Type&Screen,Used to conserve blood inventoryOn average,a surgical procedure uses about 1 unit of RBCs,however,many times the units are on“hold”in the lab and will not be needed(reducing inventory)For this reason,only a type&screen are performed and if any blood is nee
45、ded,the sample can be retrieved for crossmatching(only the IS phase is required)If antibodies are identified,then antigen negative blood is reserved or crossmatched,Neonatal Transfusion,A neonate who is 4 months old does not have antibodiesABO/Rh compatible blood is givenHowever,if clinically signif
46、icant antibodies are detected,they are usually maternal and antigen negative units are givenEither infant or maternal serum can be used for the crossmatchPedipacks are small aliquots of larger units and prepared by the donor facility or hospital lab for infant transfusion,Autologous crossmatching,Au
47、tologous refers to a donation from the recipient for later useSpecial procedures/protocols must be available so that the autologous unit is found and transfused to the recipientPretransfusion testing procedures vary,Other components,Other components to be given do not need to be crossmatched because
48、 they have been thoroughly screened for antibodiesFrozen plasmaPlatelet concentrateCryoprecipitatePlatelets pheresisGranulocyte concentratesGive ABO compatible units,New Technologies,The electronic crossmatchAccording to the AABB,the following must be fulfilled:Critical elements of the information s
49、ystem have been validated on-site.No clinically significant antibodies are detected in the current blood sample and there is no record of clinically significant antibodies in the past,Computer crossmatch(contd),The patients ABO group and Rh type has been done twice and entered in the computerThe don
50、or ABO/Rh have been confirmed and entered in the computer.The donor unit identification number,component name,and ABO/Rh type must also be entered in the computer The computer system will alert the technologist to ABO&Rh discrepancies between information on the donor label and results of donor confi
