Use of Relative Ratio to analyze Donor Specific Antibody – One center’s experience

Aim To determine whether the use of Relative Ratio (RR) calculations would prove to be a better analysis for Donor Specific Antibody (DSA) testing as opposed to the currently used MFI cutoffs. The RR calculation is thought to standardize Single Antigen tests from one run to another and allow for comparison and monitoring of trends. Methods A retrospective analysis of 12 post-transplant patients who were identified as having specific DSA detected a minimum of 3 times was conducted using the following RR calculation (presented by Deborah Crowe at the 2010 ASHI Regional Meeting): Negative Background (NBG) Ratio ∗ 100/Positive/Negative Ratio. All tests were performed using One Lambda Single Antigen Luminex kits. Results Of the 12 patients, 6 had Class I DSA and 7 had Class II DSA, based on a MFI cutoff of 1500. Cutoffs for RR have not been established for our lab, however a great variability in RR values was seen within the same patients’ tests when looking at specific DSA beads. Some patients demonstrated an expected result of high RR values at the onset of DSA that decreased as antibody reduction treatment was given to the patient, also evidenced by changes in MFI values, while others showed no such patterns. A comparison of a sample of this data can be seen in Figs. 1 and 2. Download full-size image Download full-size image Conclusions We feel that the use of Relative Ratio is a no more effective means of analyzing DSA than our current MFI-based analysis, and in some cases is less useful. The additional technologist time necessary to establish cutoffs for the lab, then re-analyze each DSA test as it is run does not make this method one we are considering adopting when our current protocol for analyzing DSAs produces satisfactory results for our patients and transplant program.