P117Clinical relevance of single antigen bead igg, igm, and c1q anti-hla antibody testing

Aim HLA single antigen bead testing for IgG antibodies has significantly improved the clinical outcome of transplantation. However, there are other single antigen bead assays, such as IgM and C1q that aid in identifying types antibodies. This study focuses on analyzing the clinical relevance of the IgG, IgM and C1q assays. Methods 28 specimens were tested using the IgG, IgM, and C1q single antigen bead assays, according to the manufacturer’s procedures. Using the raw data, percentage of positive reactivity, donor specific bead reactivity, and DSA reactivity in relation to creatinine levels were compared. Results 1. It was observed that there is a higher percentage of reactivity with IgM versus IgG in HLA-A and HLA-C. Statistically, the difference in HLA-A is significant (p 0.01) but the difference in HLA-C is not significant (p = 0.124). 2. When comparing donor specific reactivity: a. Very few samples had positive reactions with C1q and IgM but negative with IgG. b. Most positive C1q reactions were accompanied by positive IgG reactions, only. c. There was no direct link between the mean fluorescence intensity (MFI) of C1q and IgG or C1q and IgM. 3. Clinically, one case had elevated creatinine levels with no IgG, IgM or C1q DSA present. Later, that patient developed IgG, IgM and C1q DSA. In addition, there were several cases with low MFI IgG and IgM DSA, with normal creatinine levels. Conclusions Due to the difference in percentage of positive IgM and IgG reactions to HLA-C not being statistically significant, more data needs to be collected to confirm the above results. For clinical interpretation, C1q reactivity may not be predicted based on IgG, IgM, or a combination of IgG/IgM reactivity. The immune binding capability and secondary antibody dilution factor for each assay should be strongly considered. Lastly, each patient’s renal function, as well as anti-HLA antibody results, should be considered when diagnosing AMR and determining treatment.