Properties of the monoclonal protein that altered the coagualtion profile. (A) Overlaid MALDI-TOF/MS LC [M +2H]²⁺ spectra of sialidase-treated and untreated immunopurified IgG from patient 1. Arrow indicates mass shift of sialidase-treated IgG. Mass spectra similar to (A) of 2 patients with myeloma with no bleeding or coagulation abnormalities (B-C) and a normal healthy control (D). Note the absence of mass shifts in LC. (C) Smaller heavy chain mass shifts were noted with sialidase treatment (inset). (E) Table of clot-based TT measured in sialidase-treated or untreated PNP and PNP spiked with sialidase-treated or untreated immunopurified IgG from sera of patient 1 and 4 normal controls, at 1:10 ratio. The percentage decrease in TT with sialidase treatment is shown. (F) MALDI-TOF spectra of sialidase-treated or untreated immunopurified IgA from patient 2. Arrow shows a clear mass shifts in sialidase-treated IgA heavy chain (inset). No LC mass shift was noted with sialidase treatment.