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53-P: Adding affinity to the equation
Abstracts
S37
52-P
CORRELATIONS OF DONOR-SPECIFIC ANTIBODY DETECTION METHODS. Younhee Park,1 Hyon-Suk Kim,2 Dong Il Won,3 Hae Jin Kim,4 Yu Seun Kim.4 1Laboratory Medicine, Kwandong University College of Medicine, Goyang, Korea; 2Laboratory Medicine, Yonsei University College of Medicine, Seoul, Korea; 3Laboratory Medicine, Kyungpook National University Hospital, Daegu, Korea; 4Surgery, Yonsei University College of Medicine, Seoul, Korea. Aim: Donor-specific HLA antibodies are known to significantly affect graft survival in renal transplantation. Screening tests with higher sensitivity than complement dependent cytotoxicity (CDC), like the flow cytometric crossmatches (FCXm) and Luminex donor-specific crossmatches (LumXm), have been introduced in the past years. Methods: FCXM, LumXm (Tepnel Lifecodes, CT) and CDC techniques were performed from 143 patients waiting for renal transplantation between April 2008 and April 2009. The results were compared. If the ratio of median fluorescent intensity (MFI) of recipient serum to negative control serum was ⬎2 for T cells and ⬎3 for B cells, FCXm was considered positive. In LumXm, over than 3 of score using adjusted MFI was positive. Results: Twelve (8.4%) and 10 (7.0%) patients were positive in T cells and B cells from all tests. Each concordant rate from all tests and between CDC and FCXm, CDC and LumXm, and FCXm and LumXm were 85.3%, 90.2%, 88.1% and 92.3% in T cells and 70.6%, 77.6%, 82.5% and 81.1% in B cells. Minimum results of statistically significant MFI of FCXm were 2.82⫾0.62 in T cells and 10.9⫾10.10 in B cells, although MFIs were 1.01⫾0.09 and 1.14⫾0.50 from same cells of all negative groups. Conclusions: Disagreements among three tests were not so significant. The rates were higher in T cell than B cell and between FCXm and LumXm than other combinations. For a helpful clinical decision depending on laboratory tests, adjustment of MFI cut-off of FCXm should be considered.
53-P
ADDING AFFINITY TO THE EQUATION. Daniel Ramon, Ashley Brain, Anat R. Tambur. Northwestern University, Chicago, IL, USA. Aim: To evaluate efficacy of desensitization protocols, changes in MFI/MESF or actual antibody titration can be performed. When comparing the two approaches, we have noticed multiple cases in which samples with similar MESF values showed different DSA titers. We hypothesized that this phenomenon is due to differences in binding affinity. Methods: To increase SA reactions stringency a commercially available Elution Buffer (EB) was added [Aff-EB]. PBS was served as control [Aff-PBS]. Net affinity value Aff(PBS-EB) as well as an affinity ratio EB/PBS % were calculated. Serum samples were selected from patient-pairs exhibiting antibodies against the same DSA with similar MESF but with different titers. Results: Figure 1 provide two examples of the predictive value of the affinity assay. Pt1 and Pt2 both with antibodies to DR53 showed similar MESF values but different titers. The affinity assay showed stronger affinity for the patient that had actual higher titer in dilution studies. The second example shows two patients with DSA to A24. Pt4 had a higher MESF value but lower titer compared with Pt3; also predicted by the affinity studies. Similar results were obtained for all patient-pairs compared in this study. Conclusions: Many labs struggle with the ability to provide clinically valuable DSA levels. MFI/MESF values sometimes show discrepancies with actual patients’ responses to treatment. Our approach provides an easy method to characterizing the affinity and concentration of DSA for monitoring during pre and post transplant desensitization protocols.
S37
52-P
CORRELATIONS OF DONOR-SPECIFIC ANTIBODY DETECTION METHODS. Younhee Park,1 Hyon-Suk Kim,2 Dong Il Won,3 Hae Jin Kim,4 Yu Seun Kim.4 1Laboratory Medicine, Kwandong University College of Medicine, Goyang, Korea; 2Laboratory Medicine, Yonsei University College of Medicine, Seoul, Korea; 3Laboratory Medicine, Kyungpook National University Hospital, Daegu, Korea; 4Surgery, Yonsei University College of Medicine, Seoul, Korea. Aim: Donor-specific HLA antibodies are known to significantly affect graft survival in renal transplantation. Screening tests with higher sensitivity than complement dependent cytotoxicity (CDC), like the flow cytometric crossmatches (FCXm) and Luminex donor-specific crossmatches (LumXm), have been introduced in the past years. Methods: FCXM, LumXm (Tepnel Lifecodes, CT) and CDC techniques were performed from 143 patients waiting for renal transplantation between April 2008 and April 2009. The results were compared. If the ratio of median fluorescent intensity (MFI) of recipient serum to negative control serum was ⬎2 for T cells and ⬎3 for B cells, FCXm was considered positive. In LumXm, over than 3 of score using adjusted MFI was positive. Results: Twelve (8.4%) and 10 (7.0%) patients were positive in T cells and B cells from all tests. Each concordant rate from all tests and between CDC and FCXm, CDC and LumXm, and FCXm and LumXm were 85.3%, 90.2%, 88.1% and 92.3% in T cells and 70.6%, 77.6%, 82.5% and 81.1% in B cells. Minimum results of statistically significant MFI of FCXm were 2.82⫾0.62 in T cells and 10.9⫾10.10 in B cells, although MFIs were 1.01⫾0.09 and 1.14⫾0.50 from same cells of all negative groups. Conclusions: Disagreements among three tests were not so significant. The rates were higher in T cell than B cell and between FCXm and LumXm than other combinations. For a helpful clinical decision depending on laboratory tests, adjustment of MFI cut-off of FCXm should be considered.
53-P
ADDING AFFINITY TO THE EQUATION. Daniel Ramon, Ashley Brain, Anat R. Tambur. Northwestern University, Chicago, IL, USA. Aim: To evaluate efficacy of desensitization protocols, changes in MFI/MESF or actual antibody titration can be performed. When comparing the two approaches, we have noticed multiple cases in which samples with similar MESF values showed different DSA titers. We hypothesized that this phenomenon is due to differences in binding affinity. Methods: To increase SA reactions stringency a commercially available Elution Buffer (EB) was added [Aff-EB]. PBS was served as control [Aff-PBS]. Net affinity value Aff(PBS-EB) as well as an affinity ratio EB/PBS % were calculated. Serum samples were selected from patient-pairs exhibiting antibodies against the same DSA with similar MESF but with different titers. Results: Figure 1 provide two examples of the predictive value of the affinity assay. Pt1 and Pt2 both with antibodies to DR53 showed similar MESF values but different titers. The affinity assay showed stronger affinity for the patient that had actual higher titer in dilution studies. The second example shows two patients with DSA to A24. Pt4 had a higher MESF value but lower titer compared with Pt3; also predicted by the affinity studies. Similar results were obtained for all patient-pairs compared in this study. Conclusions: Many labs struggle with the ability to provide clinically valuable DSA levels. MFI/MESF values sometimes show discrepancies with actual patients’ responses to treatment. Our approach provides an easy method to characterizing the affinity and concentration of DSA for monitoring during pre and post transplant desensitization protocols.