How does the sensitivity of Mean Fluorescent Intensity (MFI) affect the outcome?

Mean Fluorescent Intensity (MFI) values are used to estimate the likelihood of a positive physical crossmatch. Because MFI technology is highly sensitive, the way thresholds are set can strongly influence whether a match is considered acceptable:

• Risk of Overestimation: If the MFI cutoff is too low, a recipient may lose the opportunity to receive a kidney from a donor who would have been compatible in the physical crossmatch.

• Risk of Underestimation: If the MFI cutoff is too high, a virtual match may appear acceptable, but then fail the final physical crossmatch.

• Memory Responses: Even when MFI levels are low and the physical crossmatch is negative, longterm risks may still exist due to the immune system’s memory responses. For this reason, previous immunologic test results—including the most recent HLA antibody screen—are taken into account. It is also important to consider the HLA typing of relatives who have donated a kidney.

Higher MFI values generally indicate a greater likelihood of a positive physical crossmatch, as seen in CDC or flow cytometry tests.