PURPOSE: Development of de novo donor specific antibody (dnDSA) following kidney transplantation is not uncommon. As laboratory techniques advance, rates of dnDSA have increased. However, with more sensitive techniques, questions arise as to the significance of these antibodies. Mean fluorescence intensity (MFI) has shown inconsistent results. We looked at antibody dilutions as an alternative method of identifying significant antibodies.

METHODS: We retrospectively analyzed data for all patients who have developed dnDSA since our current screening program began in January 2012. Antibodies were reported by MFI and the lowest titer at which they could be identified. Patients were analyzed by class of DSA, time to development, c1q positivity, titer, coincident change in renal function, biopsy findings, and antibody treatment. Statistical calculations were made using Fisher's exact test with a two tailed P value.

RESULTS: 91 patients were analyzed who had developed dnDSA following kidney or kidney/pancreas transplantation. 54 had titers of 1:64 or less, 37 had titers of 1:128 or greater. The low titer antibody group was associated with significantly better outcomes including reduction in or complete resolution (CR) of antibody (54% vs 19% p= 0.001 for CR, 74% vs 49% p= 0.016 for reduction) as well as a better chance to return to baseline renal function (85 v. 51% p= 0.0003).

The low titer group was associated with less aggressive treatment (46 v. 81% p=0.001). It also was more likely to be c1q negative (88 v. 22% p=0.0001), occur within 6 months of transplant ( 76 v. 54% p=0.04), be limited to class I antibodies (52 v. 14% p=0.0002), and not be associated with an elevation in creatinine (81 v. 54% p=0.04). Each of these variables was also analyzed as possible confounders, but with the exception of elevation in creatinine, none were found to be significant independent predictors of outcome.

Other cutoffs for antibody titer were similarly analyzed, but none showed a statistically significant impact on clinical or serologic outcomes.

CONCLUSION: Antibody titer, more than MFI, is a useful tool to help identify antibodies which have greater risk to the patient and graft. Titer was a better predictor of this than time to development, c1q positivity or antibody class.

CITATION INFORMATION: Gilbert A, Zaheer M, Timofeeva O, Rosen-Bronson S, Awwad M, Li D, Grafals M, Javaid B, Abrams P, Verbesey J, Cooper M. Antibody Titers as Predictors of Kidney Graft Outcomes. Am J Transplant. 2016;16 (suppl 3).

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