Blood Typing Discrepancies

Reverse blood typing discrepancies of patients is often due to various problems.  Often I see medical technologist assume that the patients has an cold auto such anti A1 for A patients or anti M. This assumption is usually wrong. The problem for most reverse typing discrepancies is usually rouleaux or not pre-warming.

*Some facilities SOP’s may require identifying cold agglutins  before pre-warming but these antibodies are usually considered benign. Identifying cold agglutins usually requires testing the patients serum against I negative cells.

The first step an technologist must take when investigating an ABO reverse typing discrepancy is pre-warm everything  one is testing. This encompasses the patients serum, testing reagents and pipette for 5 minutes before performing test. If the resulting test is still positive the blood banker will then observe the test tube under the microscope. If rouleaux is present the technologist must perform the saline replacement technique. This test requires removing all serum from the test tube using a pipette. *The technologist must make sure to remove all of the serum and not disturb the cell button when performing this test. After removing the serum the technologist will add the two drops of saline to the test tube and the centrifuge. If agglutination is not present the patient has rouleaux.

If agglutination is still present the patient may have rouleaux and a antibody. Further evaluations must be done such a a 3 cell antibody screen and patient history.

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