#32
FACTORS PREDICTING POSITIVE CLASS II ANTIBODY IDENTIFICAATION AND B CELL CROSSMATCH IN KIDNEY TRANSPLANT WAITING LIST SUBJECTS.
Kathryn Tinckam, MD, Dean Sylvaria, BS CHS, Isabelle Wood, BS, Fang Ji, MD and Edgar Milford, MD. Boston MA, USA, Brigham
Women
s Hospital, 02115, Tissue Typing Laboratory.
Purpose: A positive (pos.) B cell crossmatch (BCXM) may be a risk factor for kidney transplant (KTx) rejection. It is desirable, for economy and efficiency, to identify subjects more likely to have a pos. BCXM. We therefore studied KTx waiting list subjects for predictors of Class II Antibody (CIIAb) identification and pos. BCXM.
Methods: 878 subjects were consecutively identified and serum samples were collected from 03/25/03 to 04/08/03. A peak Class I Ab (CIAb) PRA within 6 months prior to study entry was obtained and its predictive value, with other relevant covariates, for CIIAb determined. In 99 of these subjects, stability of CIIAb results was studied over 9 months. In 188 consecutive subjects evaluated for living donor transplant between 9/12/02 and 03/30/04, predictors of pos. BCXM were evaluated (including ClassII FlowPRA (CIIFP), age, sex, prior transplant, and HLA mismatches).
Results: 220 subjects (25%) had CIIAb detected. Female sex (34.1% vs 17.8% male, p<0.001), retransplant (68.6% vs. 15.7% 1o KTx p<0.001) and CIAb>10% (62.0% vs 8.6% CIAb<10%, p<0.001) had pos.CIIAb. CIIAb results were unchanged over 9 months in 98% of subjects. Pos.CDC BCXM occurred in 44/188 subjects (23% ).CIIFP>2%(OR 63.0 [19.6,202.4]) and female gender(OR 5.6 [1.7, 18.0]) predict subsequent pos.BCXM after adjusting for all other relevant covariates. Specificity and NPVof CIIFP>2% for pos.BCXM is 92% and 95% respectively. PPV of FlowPRA>2% for pos.ELISA is 100% in our lab.
Conclusions: We propose an algorithm for CIIAb screening based on CIAb status and sex. CIIAb identification predicts pos. BCXM and may be used to efficiently identify subjects requiring BCXM at the time of KTx.