Lab Tips

Failed crossmatches can be devastating for NKR chains because one failure often affects many potential transplants. A single unexpected crossmatch failure in NKR can impact eight or more surgeries. Crossmatch failures are also costly when tests at other centers are performed for patients who cannot proceed to transplant.

Although some crossmatch failures are unavoidable, most can be prevented by the HLA laboratory by playing a proactive role in donor selection. Virtual crossmatch accuracy is a measure of how well a transplant center’s lab performs as compared to their peer group.

The NKR has invested in high-resolution typing and developed tools to preview potential donor matches. In addition, we have made it easy to perform exploratory crossmatches on potential donors for sensitized patients through cryo-preserved donor tissue.

Using these tools will improve your patients’ chances for transplant and will reduce unexpected crossmatch failures. Good communication and understanding between the laboratory, coordinators, physicians and surgeons is a key to success in paired exchanges.

Establish an understanding of your crossmatch results with the transplant team

  1. Convey the importance of avoiding or at least reporting potential sensitizing events to the transplant team and to the laboratory.
    1. Patients should notify the transplant team prior to being transfused, having surgery, etc. Retest patients whose antibody profiles may have changed.
  2. Review patients with special requirements for compatibility (e.g. children, patients unable or unwilling to accept a donor with potential incompatibilities).
  3. Establish clear crossmatch thresholds with your transplant team.
    1. Borderline positive or negative results may change with retesting.
    2. Flow cytometry results are semi-quantitative, rather than a dichotomous positive or negative, flow values provide an indication of increasing risk.
  4. Anticipate confounding crossmatch results.
    1. Screen for IgM or autoantibodies.
    2. Treat patient sera with DTT or EDTA to reduce prozone effects in solid-phase tests.
    3. Test sera at dilution to identify weak antibodies or antibodies at saturation.
    4. Be careful enrolling patients in KPD with non-HLA antibodies that may preclude a transplant.

Personalize the virtual crossmatch to get the most compatible donors for your patient

  1. List all DSAs.
  2. List more low level avoids for easy-to-match pairs (cPRAs < 95%) since they will have many potential donors.
  3. List more low-level avoids for patients who will not tolerate aggressive immunosuppression, plasmapheresis or who otherwise require a completely DSA-free transplant.
  4. Look for donors with a low or zero eplet mismatch in combination with DSA avoidance in the pre-select screens.

Use the NKR pre-select screens for difficult to match pairs

  1. Review donors with one avoid HLA antigen in the avoid conflict tab.
  2. Determine whether desensitization is feasible for specific incompatibilities.
  3. Review ABOi donors for 100% CPRA patients (ABOi is often less difficult than desensitization for HLA).

Evaluate patients with allele-specific antibodies

  1. Review the third-generation typing results provided by the NKR lab to find donors without allele specific antibodies.
  2. Use tools like the epitope registry ( to evaluate allele reactivities in the context of shared potential epitopes.

Use exploratory crossmatches with donors for hard-to-match patients who have:

  1. A weak DSA.
  2. Multiple low-level DSAs.
  3. Cw, DQ or DP DSAs with uncertain crossmatch potential.
  4. Allele-specific antibodies not likely to react with a selected donor.
  5. Exploratory XMs should be requested as soon as the potential donor becomes available via pre-select.
  6. Exploratory XMs using NKR supplied cryo cells should be completed in 1-day.