What additional testing should be done on the specimen?

  1. The first step to resolve any discrepancy is to confirm that the test was performed correctly. This involves performing a clerical check of the specimen label information, comparing it to the test tube label information and the request form information. If all information is consistent, start over and repeat the entire test (in this case the ABO) using a new cell suspension. This step is often overlooked but is essential to ensuring technical accuracy before proceeding to investigate clinical reasons for the discrepancy.

    See complete investigaton steps.

    In this case the discrepancy is a missing reaction with the A1 cells in the reverse grouping.

  2. The next step would be to enhance the reverse grouping. This may be accomplished in several ways:

    1. Add more serum or plasma to the reverse grouping cells and re-centrifuge. This will increase the antibody-to-antigen ratio and enhance agglutination.
    2. Increase the incubation time, which will allow more time for the antigen and antibody to react.
    3. Incubate the reverse grouping at 4° C. It is important to include an autocontrol using the patient’s serum (or plasma) and red cells. Omitting an autocontrol may result in not detecting false positive reactions due to cold autoagglutinins.