Automated CD61 immunoplatelet analysis of thrombocytopenic samples.

Revision of the current decision point for prophylactic platelet transfusion in thrombocytopenic patients requires the availability of a method that is able to provide accurate platelet counts to as low as 1 x 109/l. This study is the first to evaluate the immunoplatelet method (CD61-Imm) of the haematological analyser Cell-Dyn 4000 in direct comparison with the flow cytometric procedure. Additionally CD61-Imm results were compared with CD4000 optical (Plto) counts in the ranges 20-547 x 109/l (n = 127) and 1-35 x 109/l (n = 107). The immunoplatelet and Plto results were in good agreement between 20 x 109/l and 547 x 109/l, but for samples of < 25 x 109/l the Plto tended to overestimate the counts. We determined the limits of detection (LD) and quantification (LLQ) for all three methods using standard statistical procedures. The LD for the flow cytometric CD41a method was 0.02 x 109/l compared with 0.009 x 109/l and 1.73 x 109/l for the CD61-Imm and Plto methods respectively. The LLQCV = 15% for the CD41a method was 1.8 x 109/l compared with 1.6 x 109/l and 18.0 x 109/l for the CD61-Imm and Plto procedures. In conclusion, (i) the CD61-Imm method performance is at least equivalent to the reference flow cytometric method, and (ii) in severe thrombocytopenia the CD61-Imm count is superior to the Plto count.