Upload
erin-oneal
View
390
Download
3
Tags:
Embed Size (px)
Citation preview
Compatibility Testing (cross matching)
Compatibility testing
PurposePurpose Selection of safest blood components for transfusion With acceptable donor’s red cell survival rates Without destruction of recipient’s red cells
Compatibility testing Compatibility testing Confirms ABO compatibility Detects clinically significant unexpected antibodies
Importance of cross matchingImportance of cross matching
Routine blood grouping involves only ABO and Rh. Other clinically significant blood group systems
not matched routinely Though, antibodies to minor antigens are of rare
occurrence, they can cause transfusion reactions Cross matching between patient’s serum and
donor’s cells will detect antibodies to other blood groups, if present.
1. Identification of patient & its sampleo patient full name & hospital registration #o name of requesting physiciano date & time of sample collectiono initials of phlebotomisto information clearly written on requisition form and
sample
2. ABO & Rh of recipient and donor blood3. Test for clinically significant red cell antibodies
on patient serum
Steps in pre-transfusion testingSteps in pre-transfusion testing
4. Selection of appropriate unit of blood ABO & Rh compatible Expiration date Component as per need of patient
PRBC, FFP, PC, Cryo
5. Performance of serological cross match
6. Labeling of component with patient identification details
7. Issue after verification of patient identity along with compatibility report & reaction form
Steps in pre-transfusion testingSteps in pre-transfusion testing
Pre-transfusion testing procedure
Donor Unit Testing Donor Unit Testing ABO grouping: Forward and Reverse Rh grouping: Rh (D) including weak D (Du)
Recipient TestingRecipient Testing ABO grouping: Forward and Reverse Rh grouping, Weak D (Du) not required IAT testing: Antibody screen Cross match: Major & Minor
Major crossmatch: Test donor cells with recipient’s serum to detect antibodies in patient serum
Minor crossmatch: Test donor serum with recipient’s red cells to detect antibodies in donor serum
Inclusion of autocontrol helps to rule out Auto antibodies Allo antibodies Rouleaux formation
Serological cross matchSerological cross match
Preparation of donor cells for cross-matching
Select appropriate unit of blood from inventory Check for
o Donor ID o Blood Group o Expiry dateo Hemolysis / leakage
Detach a segment from the blood bag, cut ends of segments and pour the contents in a labeled test tube
Wash red cells with saline 3 times and prepare 5% suspension
• Donor cells are taken from segments that are attached to the unit itself.
• Segments are sampling of the blood and eliminate having to open the actual unit.
Clinically significant Abs
• Abs regarded as always being potentially clinically significant;ABO, Rh, Kell, Duffy, Kidd & S s U
• Abs that may sometimes be clinically Significant;Lea, p, Lua, Lub & Cartwright.
• Other Abs are rarely if ever, clinically significant.
Cross Matching Procedure
Cross matching should be performed at following phaseso Saline phase at room temperatureo AHG phase
Cross matching can be performed using conventional test tubes or by using newer technologies such aso Column Agglutination Technologyo Solid Phase Technologyo Electro Magnetic (EM) Technology
Immediate Spin Technique (IST)Immediate Spin Technique (IST)
Detects only IgM antibody, reactive at 22oC.
Clinically significant IgG antibody reactive at 37oC not detected
Patient serum
2 drops
Donor RBC
1 drop, 5%
Immediate centrifuge
ABO incompatibility
22oC
Conventional AHG-crossmatchConventional AHG-crossmatch
Patient serum
2 drops
Incubation37oC, 1 hr
Donor RBC
1 drop, 5%
3 washes
Centrifuge
2 drops AHGMix properly
Agglutination = incompatible
No agglutination = compatible
Detects clinically significant (IgG) antibody
Serological cross match
PhasePhase DetectsDetectsIS phase ABO incompatibilities
AHG phase Rh, Duffy, Kidd, others
Points to remember: Preserve recipients serum & donor red cell segment for a week.
However, fresh sample of the patient is needed after 48 hrs of transfusion
Do not withdraw sample from the IV line
Infuse red blood cells within 4 hours
Cross matching Procedure • If antibodies ARE detected:
– Antigen negative units found and X-matched
– All phases are tested: IS, 37° & AHG
– This termed as COMPLETE CROSSMATCH
Cross matching for platelets & plasma No compatibility testing required for platelets and plasma components
Only ABO matching is required for fresh frozen plasma
No need for compatibility, ABO and Rh matching for platelet concentrates and cryoprecipitate
Exceptions
Neonates, alloimmunized patients – preferably ABO & Rh matched platelets
Incomplete requisition forms
Hemolyzed samples
EDTA and clotted sample
oPlasma prevents detection of complement
dependent antibodies
oFibrin clots, which may form, can be mistaken for
agglutination
Problems In Cross MatchingProblems In Cross Matching
Incompatible crossmatches
Antibody Antibody screenscreen
Cross Cross matchmatch
Cause Cause ResolutionResolution
Pos Neg Antibody directed against antigen on screening cell
ID antibody, select antigen negative blood
Neg Pos Antibody directed against antigen on donor cell which may not be on screening cell OR donor may be DAT positive
ID antibody, select antigen negative blood OR perform DAT on donor unit
Pos Pos Antibodies directed against both screening and donor cells
Antibody ID, select antigen negative blood
Normal sampleHemolyzed
Expired / contaminated reagents Improper cell concentration (cell : serum ratio) Labeling errors Improper washing of red cells before forward grouping Equipment – Improper centrifugation Dirty glass wares Reading and recording reactions
oGrading of reaction strengthoHemolysis – positive resultoAuto-agglutination
Technical ProblemsTechnical Problems
Clinical urgency Clinical urgency
Immediate Within an hour Minutes
Group O Rh neg Packed RBCs
ABO & Rh D type
Group specific blood
ABO & Rh D type
Complete crossmatch
Cross matching: Special CircumstancesCross matching: Special Circumstances
If units are issued without X match – take written consent of physician, complete X match after issue
Neonatal (< 4 months) Transfusions Only ABO and Rh grouping; no serum grouping Antibody screen with maternal serum Exchange transfusion:
o WB or PRBCs within 7 days of collectiono ABO and Rh D compatible with maternal sampleo Irradiated unit for infant weight < 1500 gm
Cross Matching: Special circumstancesCross Matching: Special circumstances
Transfusion in AIHA Avoid transfusion as far as possible in Warm AIHA There could be problems in blood grouping
o Spontaneous agglutination of red cells on addition of antisera in WAIHA
o Non specific agglutination of reagent cells during serum grouping in cold AIHA
Difficult to find absolutely compatible blood for such patients. In emergency, consider the least incompatible blood.
o Blood unit showing minimum strength of reaction in terms of titer designated as the ‘least incompatible’.
o Blood unit must be compatible with the patient's auto-absorbed-serum.
Transfusion should be done under strict medical supervision.
“Dangerous group O donor” In emergency situations group ‘O’ donor blood is used as universal donor where group identical blood is not available. This is an outdated concept in major blood banks. Certain donors possess in their plasma potent ABO antibodies, which are dangerous to the recipients’ red cells. These are anti A and anti B haemolysins, titer of which is > 32 Such donors are called as “dangerous O donor” Therefore, if group O blood is to be used as universal donor, it should always be plasma depleted (packed red cells)
Red blood cell compatibility table
AB+
AB-
B+
B-
A+
A-
O+
O-
AB+AB-B+B-A+A-O+O-
DonorRecipient
Plasma compatibility table
O
B
A
AB
AB
BAO
DonorRecipient
IATIAT
• Patient plasma and O negative pooled cell• 30-60 min incubation in 37ºC• Wash 3 times • Add PS-AHG• For more precision in negative results please check with:• Microscope, check cell and elution
• PH, time, ionic power, Ab: Ag ratio are important• LISS, PEG, Polybern, 22-30% albumin can be used for special purposes
IATIAT
• PEG enhances the reaction of anti kidd with low titers• 22-30% Albumin enhances the reaction of anti RH and anti P1 in 37ºC• Anti K doesn’t have good reaction in LISS solution
DATDAT
• 2-5% suspension of RBCs should be prepared• EDTA anticoagulated blood• Wash 2-3 drop of blood for 3-4 times• Wash with press of saline between each centrifuge : cell pellet will be
suspend and negative result wont appear. • In multiple myeloma and WM wash 6 times• Immediately add 2 drops of PS-AHG and spin(30 seconds in 3000 rpm)• If agglutination observed : DAT positive• If the result was negative : incubate 5-10 min in RT(C3d)• If the result was negative : add2-3 drops of CC
Check cell preparationCheck cell preparation
• Check cell: • 1 drop of 1:4000 of diluted serum can corrupt 1 drop of AHG• Then any contamination with serum may lead to AHG negative result• preaper 5% suspension of Rh pos cells• You can use Anti D or RhoGam• Dilute the anti body• Add 250 micro liter suspension to each tube of .5 ml RBCs• Incubate in 37ºC for 30 minuets• Then centrifuge at 3000 rpm for 1 minuete
Check cell preparationCheck cell preparation• Select the first negative tubes and wash 3 times. For example 1:32 and 1:64
and 1:128• Add AHG and centrifuge• +2 agglutination should be noticed