BACKGROUND AND AIMS: The prozone effect is one factor causing false negative reactions in HLA antibody testing. EDTA, which is commonly used to remove this effect, may result in the identification of HLA antibodies that were previously masked by prozone. These unmasked antibodies may in turn, increase the number of unacceptable antigens entered into UNOS. The current study aimed to determine whether the unacceptable antigens submitted to UNOS changed after the implementation of EDTA serum-treatment. Furthermore, we investigated cPRA changes, in particular, those leading to cPRA >98%.

PATIENTS AND METHODS: We retrospectively reviewed the reports that our laboratory submitted to UNOS on behalf of renal transplant candidates whose monthly samples were tested in our laboratory pre- and post-implementation of EDTA serum-treatment. A total of 199 patients were included in this study. The reports pre- and post-implementation of EDTA treatment were reviewed and compared for cPRA and unacceptable antigens reported to UNOS.

RESULTS: cPRA increase after EDTA treatment was observed in 45 of 199 patients (22.6%). By reviewing the dilution results for these patients, we identified 19 patients (42.2 %) with prozone effect. The distribution of prozone effect included 64.4% class I antibody, 16% class II, and 20% in both class I and class II. Importantly, among these 45 patients with cPRA increases, 8 of them (17.8%) had a cPRA greater than 98% after EDTA treatment.

CONCLUSION: The analysis of single antigen beads' MFI revealed that EDTA treatment removed the prozone effect in all tested samples and unmasked strong antibodies. Accordingly, the number of unacceptable antigens and cPRA were increased in patients with prozone effect. The removal of prozone effect by EDTA treatment led to an increase in patients with cPRA greater than 98%, which has a direct impact on patient's priority on the waiting list.

CITATION INFORMATION: Xin J, Brown N, Upchurch R, Weidner J, Marino S. Impact of Serum EDTA Treatment on Identification of Unacceptable Antigens for Kidney Transplant Candidates. Am J Transplant. 2017;17 (suppl 3).

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