Question

You are working second shift at a rural hospital. Although you were trained in using gel technology, your lab utilizes the conventional tube testing methods using LISS as an enhancement medium. An hour before the end of your shift, the phlebotomist brings a routine type and screen for a patient just admitted to the medical surgical ward. You decided to proceed with testing. The patient typed as A-positive. The antibody screen results were negative in all phases of testing. Therefore, check cells were added to all tubes and the reactions after centrifugation were also negative.

1. Can the antibody screen be interpreted as negative?

2. What steps must be takeh to resolve the problem?

3. What is the most likely cause for the discrepant results?

4. What are other causes for the results?

Answer 1

1. Antibody screen results cannot be interrupted as negative.
2. Testing plasma by various test methods

• Testing a panel even when the Ab screen is negative
• Testing low-prevalence Ag- positive cells

1. Antibody screening cells don’t carry all antigens.

• IgM antibodies less reactive in solid phase
• Anti-Jka is only detectable in solid phase
• Antigen may be only on a donor’s red cells when a single XM is incompatible

1. Antigen may be present but test system will not adequately detect: test method or difference in antigen dosage between Ab screen cells and crossmatch

• Antibodies may be directed at antigens not on Ab screen cells: HDFN, unexpected incompatible XM.

answered by: anonymous