Table 3.

Prospects for implementing HLA‐Ab detection into the AMR classification in cardiac transplantation: limitations and potential solutions

Problem	Interpretation	Resolution
HLA‐Ab to denatured antigens	False positive results: HLA‐Ab to cryptic epitopes, clinically irrelevant	Repeat testing after acid treatment of SAB; surrogate crossmatch
Intrinsic and extrinsic factors inhibiting the SAB assay	False low MFI or negative results: due to inhibition of SAB assay	Dilution of sera pretesting, adsorption, inhibition of C1q, addition of EDTA, heat treatment to remove and uncover the real reactivity
Low MFI on SAB resulting in higher reactivity using cellular targets	False low MFI: DSA to a shared target present on multiple beads	Adequate analysis of specific DSA epitope
Using MFI to evaluate level and strength of DSA for risk stratification	Low or high MFI level of DSA may not correlate with risk of AMR, or response to treatment following antibody removal therapies	Modified SAB assay to distinguish between complement and noncomplement binding DSA and determining titer of DSA (serial dilutions of patient sera)

Ab, antibody; AMR, antibody‐mediated rejection; DSA, donor‐specific antibodies; EDTA, ethylenediamine tetraacetic acid; MFI, mean fluorescence intensity; SAB, single‐antigen bead.