Pre-autologous bonk marrow transplant (abmt) screening for hla antibodies does not predict for platelet alloimmunization post-abmt: a case controlled study

In patients with bone marrow failure, up to 30% of all cases of platelet refractoriness are due to HLA alloimmunization. At our institution, ail ABMT candidates are pre-screened for HLA A, B antibodies using the standard microlymphocytoxicity test. We performed a retrospective case controlled study to determine the value of this test to predict for development of HLA alloimmunization. Patients with positive tests who arc refractory to random donor platelets receive single donor platelets (SDP); if no increment occun> then HLA matched platelets are provided. Patients with negative tests who develop platelet refractoriness have a repeat test and if positive, receive HLA matched plateiets. Transfusion products are irradiated, non-leukodepleted and matched for CMV status. Between 1/1/95 and 31/12/96, 18/221 patients had a positive screening test (8 NHL, 3 myeloma, 3 breast cancer, 2 AML and 2 HD) prior to ABMT, The HLA antibody subtypes detected included: B7 (3), B8 (2), A2 (2) and A9 (2). Four patients had polyspecific antibodies and 8 had weakly positive (unclassified) antibodies only. There were 10 males and 8 females. One patient was not évaluable. The remaining 17 (the index group) were compared to 17 controls matched for age, sex, diagnosis and ABMT intensive therapy. A total of 815 platelet units were transfused to the index group (including 15 units SDP and 120 units HLA matched platelets) versus 796 units to the control group (p~NS). Median 18-24hr corrected count increments (CCI) for index, patients was 3400 (range 0-11800); and 4600 (range 2500-13900) for controls (p=NS). One hour CCI were performed if clinically indicated (in 10/17 index and 4/17 control patients). Median Ihr CCI was 3700 (range 400-18500) and 5000 (range 1100-16800) in the index and control groups, respectively (p-NS). Three index patients and no controls developed platelet alloimmunization after ABMT as inpatients (p~NS). The positive predictive value for development of platelet alloimmunization in patients with a positive pre-ABMT screen was 17.6%. We conclude that pre-ABMT screening for HLA antibodies prior to ABMT does not predict for platelet alloimmunization and should not be routinely performed.