Detection of oxaliplatin-dependent platelet antibodies by using flow cytometry. Patient's serum, but not normal serum, reacted with group O platelets in the presence of oxaliplatin 0.1 mg/mL (black histograms) but not in its absence (gray). No reactions were obtained with fluorouracil (5-FU) or leucovorin (not shown). Numbers shown above for each histogram represent the median fluorescence intensity (MFI) values, in log scale.