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ABO Grouping

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2. ABO Grouping

Aim of this subsection is to make the medical officers understanding the principle of ABO grouping so that they can perform accurate basic blood grouping test.

ABO Grouping Techniques

Principle

The principle of ABO grouping is based on a specific agglutination reaction between antigens on red cells and IgM antibodies in the tyuping serum. Cell grouping is determined by testing an individual’s red cells with known blood grouping reagents and the corresponding serum grouping with known A cells, B cells and 0 cells.

Practical Aspects of ABO Grouping

1. ABO grouping tests should be done at room temperature (2Oo24oC) or lower; testing in hot environment weakens the raction.

2. Routine ABO grouping must include both cell and serum testing as each serves as a check on the other.

3. Antisera used in the ABO grouping must be used as per the manufacturer’s instructions.

4. Adequate controls should be put with each batch of tests for quality control of the reagents, alternately once a day the reagents must be checked with appropriate cells. Before use all the reagents must be checked grossly to rule out any turbidity or contamination.

5. Tubes, slides, tiles, microplates or gel cards should be labelled properly. One should not rely on the colour of the dye to identify the antiserum.

6. The glassware used should be dry and clean.

7. Serum should be added before adding cells and each tube should be examined after serum has been added to ensure that none has been missed.

8. Results should be recorded immediately after observation.

9. Concave mirror (agglutination viewer) or microscope may be used to examine reactions that appear negative by the naked eye.

ABO grouping sera

It is essential to use reliable grouping reagents to obtain correct results. Commercially prepared polyclonal (human source) and monoclonal (tissue culture) antisera are available. Monoclonal antisera give more specific reactions and are very sensitive for weaker reactions.

Adequate quality control must be done before purchasing commercial antisera. Each batch of antisera must be checked against A1,A2, (if available, otherwise A group) B and 0 cells before use and should be put to routine use onlyw hen unequivocal results are obtained.

The potency of any antisera deteriorates rapidly if kept for too long at ambinet temperature, groupign sera should therefore, be kept at 4°C or as directed by the manufacturer when not in use. Frozen antisera must be completely thawed before use and no refreezing should be done.

Blood sample for ABO grouping

1. Properly labelled samples of clotted blood collected in screwcapped plain test-tube are most suitable for ABO grouping. Ths amples should be stored at 4°C and preferrably be tested within 48 hours.

2. Haemolysed samples are not suitable for testing.

3. The blood sample may be centrifuged at 1000-3000 rpm for 3 minutes for adequate serum separation.

4. Separated serum should be placed in a prelabelled tube for serum grouping and other serological tests.

5. Cells from the test sample should be washed in 0.9% nromal saline and a 2-5% cell suspension should be prepared.

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