Terminal α(2-6)-linked sialylation on VWF is significantly reduced in patients with low VWF compared with controls. Lectin plate-binding ELISAs were performed in plasma samples collected from 110 patients with low VWF (▿) and compared with O blood group-matched control subjects (○). N- and O-linked sialylation on VWF were assessed using the lectins SNA, MAL-II, and WGA. As indicated in the illustrations, SNA (A) binds preferentially to terminal α(2-6)-linked sialic acid (NeuAc), which is predominantly expressed on the N-glycans of VWF; MAL-II (B) has affinity for terminal α(2-3)-linked sialic acid expressed on the O-glycans of VWF; and WGA (C) binds to sialic acid with a preference for α(2-3)-linked rather than α(2-6)-linked sialic acid residues, but also recognizes exposed N-acetylglucosamine (GlcNAc) residues. All ELISAs were performed in duplicate and results expressed as a percentage of binding to reference plasma (100%), using the slope of different dilutions. SNA binding was significantly reduced in patients with low VWF compared with controls. **P < .01, Mann-Whitney U test.