Application of flow cytometry to measure anti-A/B antibody in ABO-incompatible kidney transplantation

The aim of this study was to compare anti-ABO antibody levels as measured by means of flow cytometry (FCM) with the levels measured with the use of the column agglutination test (CAT), and to evaluate the clinical outcome as it relates to the baseline mean fluorescence intensity (MFI) ratio obtained by FCM.

We reviewed 21 cases of ABO-incompatible kidney transplantation (ABO-i KT). In these patients, baseline IgG titers were measured with the use of both FCM and CAT methods. We investigated the correlation between levels measured by FCM and those by CAT with the use of correlation coefficients. Patients were classified into a high MFI ratio group (≥200; n = 7) or low MFI ratio group (<200; n = 14).

The MFI ratio for the FCM-based method was highly correlated with the titer measured by CAT (r = 0.890; P = .01). The relationship between MFI ratio and CAT titer can be expressed as follows: log (MFI ratio) = 0.879 × log (CAT titer) + 0.298. The number of pre-transplantation rounds of plasmapheresis significantly increased as the baseline MFI ratio increased. The allograft function was immediately recovered and stable. A single case of acute cellular rejection was observed in the low MFI ratio group.

Anti-ABO antibody levels measured by means of the FCM-based method were highly correlated with the levels measured with the use of CAT in cases of ABO-i KT. The decreased level of anti-ABO antibody measured by means of FCM after plasmapheresis suggests its potential as an effective and objective method for assessment of anti-ABO antibody levels.