Case Scenario: Crossmatch Is Positive, What to do?
Case Study: 45 y/o male with ESRD and on MHD with permacath for 2 months, presents for transplant with wife as donor. During his workup he is found to be Hep C positive, with the rest of his workup being normal, including Liver. His Immunological workup is below.
| Sensitization History | None | |||||
| HLA Typing | A | B | C | DR | DQ | DP |
| Donor (A+) | 02:01, 11:01 | 13:02, 57:02 | 06:02, 18:02 | 15:03, 16:02 | 05:01, 06:01 | 02:01, 05:01 |
| Recipient (AB+) | 30:01, 24:02 | 08:01, 40:01 | 03:03, 07:02 | 09:01, 17:01 | 03:03, 02:02 | 03:01, 07:01 |
| XM | T cells | B Cells | ||||
| CDC XM | Positive | Negative | ||||
| Flow XM | Negative | Negative | ||||
| Single Antigen Bead | Class I : No anti HLA Abs | Class II: No Anti HLA Abs. |
Questions & Answers
Q1. How is a CDC XM done?
Ans: Donor cells, recipient serum incubated, Complement added and then vitality dye to assess for viability. If Antibodies against cell present then membrane attack complex formed and cell shows up as not viable. T for class I, B for class I and II.
Q2. Why is this CDC XM positive?
Ans: Likely false positivity due to hypergammaglobulinemia of HCV, may even be autoantibodies. How would you confirm your suspicion ? – Auto-crossmatch and a negative single antigen bead test show that these antibodies are not Anti- HLA antibodies.
Q3. What may be causes of false positive CDC XM?
Ans: Autoantibodies, IgM (Treat with DTT), non specific cross-reactive antibodies, poor test technique: no viable B cells, poor controls.
Q4. What may be causes of false negative CDC XM?
Ans: Meaning CDC negative but anti-HLA antibodies are present) Low level titer of anti- HLA antibodies, non complement binding antibodies.
Q5. What does a positive CDC XM predict?
Ans: Early acute rejection and hyperacute rejection. Terasaki original paper shows the utility of the test. Terasaki,P NEJM 1969: 280 (14):735-9
Q6. What will you do for this transplant pair?
Ans: Move forward for transplant with normal immunological risk.
