Principle: | Clinical Significance: | Specimen: | Materials: | Reagents: | Standardization: N.A. | Procedure: | Limitations: | Results Derivation: | Expected Result(s) | Quality Control: | References:
Patient plasma/serum is tested with Group O reagent red cells, possessing known antigens, by methods that will demonstrate clinically significant coating, hemolyzing and agglutinating antibodies at the antiglobulin phase. In this test, the red blood cells, suspended in a hypotonic-buffered saline solution, are mixed with patient plasma/serum, incubated, and centrifuged through a gel microtube containing anti-IgG. If sensitization has occurred, agglutinates of red cells will be trapped in the gel. If sensitization has not occurred, the red cells will move freely through the gel, forming a button at the bottom of the microtube.
The Gel test, a potentiated (LISS) and antiglobulin phase technique, is the method used for routine antibody detection.
II. Clinical Significance:
The antibody detection procedure is designed to detect unattached immune antibodies in a patient’s plasma/serum using anti-human globulin following plasma/serum incubation with red cells of known antigenicity. Almost all clinically significant antibodies react at 37°C and have been formed due to sensitization to red blood cell antigens from past transfusions or pregnancies. A positive antibody screen (antibody is present) needs to have an antibody identification performed and an antibody titer may be indicated in the prenatal patient.
Antibody identification is necessary to determine the clinical significance of the detected antibody and the likelihood of obtaining compatible blood. Clinically significant antibodies are those that are known to cause transfusion reactions or decreased red blood cell survival. A patient with a clinically significant antibody must only receive blood that is negative for the corresponding antigen to ensure the best possible patient outcome.
Note: Recently transfused patients who have been sensitized may not yet exhibit detectable antibody levels.
Refer to the Specimen section of the “General Processes, Blood Bank” protocol.
Note: The technologist performing the testing on the patient sample must confirm that all identifying information on the request form agrees with that on the specimen tube label before using the specimen for blood grouping, typing or antibody detection. This is noted by placing a checkmark by “Specimen Integrity” on the requisition for the test.
Refer to the Materials section of the “General Process; Blood Bank” protocol for vendor and product information.
1. MTS Incubator
2. MTS Centrifuge
3. ID TipMaster
4. MTS Pipette Tips
5. Marking Pen (water resistant)
Refer to the Reagents section of the “General Process; Blood Bank” protocol for vendor and product information.
1. MTS Anti-IgG Gel Card
A. Store gel cards upright at 2 - 25°C.
B. Visually inspect the gel cards before use. Each microtube should have a clear liquid layer on top of the opaque gel.
C. DO NOT USE A GEL CARD IF:
a. the gel matrix is absent or the liquid level in the microtube is at or below the top of the gel matrix.
b. the gel card shows signs of drying, discoloration, bubbles, crystals or other artifacts.
c. the foil seals appear damaged or are opened.
2. 0.8% Prediluted Antibody Screening Cells
VI. Standardization: N.A.
1. Check the previous patient records to determine if an antibody has already been identified.
Note: It is possible to miss a previous antibody that has decreased below detectable levels but may still cause a delayed transfusion reaction.
2. If records indicate previous antibody(ies) identified for this patient, retrieve all past workup records to use as an aid to help determine serological testing methods.
3. Label an MTS Anti-IgG Gel Card™ with the Selectogen number(s) and a patient identifier (name, number, or initials).
Note: Visually inspect the Gel Card before use.
4. Remove the foil seal from as many microtubes as needed.
Note: Remove foil immediately before or within 1 hour of testing.
5. Set the ID TipMaster to deliver 50 µl.
6. Mix the 0.8% Selectogen suspension by slowly aspirating and dispensing the suspension with the ID TipMaster.
7. Aspirate enough of the well-mixed 0.8% Selectogen(s) with the ID TipMaster to discard a portion as a primer and still be able to deliver a 50 µl aliquot.
8. Deliver 50 µl of each 0.8% Selectogen to the correct microtube on the appropriately labeled Anti-IgG Gel Card.
9. Set the ID TipMaster to deliver 25 µl.
10. Aspirate enough of the patient plasma/serum with the ID TipMaster to discard a portion as a primer and still be able to deliver a 25 µl aliquot.
11. Add 25µl of patient plasma/serum to the correct microtube(s).
12. Read and record the temperature of the Gel Card incubator.
13. Incubate the Gel Card at 37°C for 20-25 minutes. (Incubation may be extended to 30 minutes.)
14. Centrifuge the gel card for 10 minutes.
15. Read the front and the back of each microtube macroscopically against a white background after centrifugation and record the reaction. (Refer to the policy: “Reading and Grading Reactions; Blood Bank”.)
In some low ionic strength systems certain antibodies, such as Anti E and Anti K have been reported to be nonreactive.
IX. Results Derivation:
1. Negative: No agglutination or hemolysis seen, indicating the absence of an antigen/antibody reaction.
2. Positive: Agglutination or hemolysis seen, indicating the presence of an antigen/antibody reaction.
Note: Antibody identification must be performed for all positive antibody detection tests. (Refer the specimen with an Antibody Identification request to UCL Mercy.)
X. Expected Result(s) and/or Critical Values:
XI. Quality Control:
Quality control is performed per protocol. Instruments and equipment are tested as prescribed in the Maintenance and Function Verification procedures.
1. Committee on Standards, "AABB Standards for Blood Banks and Transfusion Services." American association of Blood Banks; current edition.
2. Technical Manual. Bethesda, MD: American Association of Blood Banks; current edition.
3. Anti-Human Globulin Anti-IgG (Rabbit) MTS Anti-IgG Card® package Insert. Pompano Beach, FL: Micro Typing Systems, Inc.; current version.
i. April 1996 S. Rodriguez, N. Comb.
ii. December 1997 S. Hosch (Revised: changed diluent to MTS Diluent 2®)
iii. November 1999 M. Burger (Revised: III. second note added)
iv. June 2001 M. Burger, S. Rodriguez (Revised: III., IV., VII.2., XI.)
v. September 2005 M. Burger, S. Hosch, S. Rodriguez (Revised: combined Antibody Identification and Detection [MTS Gel Card] procedures)
vi. June 2007 N. Combs (Revised: VII.2.)
vii. October 2008 N. Combs, M. Burger (Revised: for Medical Associates)
Interim Review: October 2010 N. Combs (Revised: III.note; IX.note)