Reasons for the negative panel and donor results include:
- pre- and post-transfusion specimens are not from the same person
- pretransfusion specimens are grossly contaminated
- technologist made a technical error and obtained false-positive results with the pretransfusion specimens
- blood specimens taken post-transfusion were incorrectly drawn from the arm with the IV line and taken above the line, thus contaminating them with IV fluid that diluted the patient's antibody
While these are possible explanations for the discrepant results, given the positive DAT with MFAon the post-transfusion specimen, they are unlikely.
- The negative results are most likely because most or all of the patient's antibody has adsorbed to antigen-positive transfused donor RBC
- Antibody detection tests are not 100% sensitive. The patient's antibody strength may now be below the threshold detectable by the gel test.
Note: To identify the now very weak antibody, depending on their policies and technical capacity, the TS laboratory could try other antibody detection techniques, e,g., PEG, solid phase adherence assay, enzymes. Enzymes are sensitive for Rh and Kidd system antibodies but known to destroy some antigens, e.g., MNS and Duffy system antigens.