(determined by doing an FVIII or FIX assay on a venous blood sample). The severity is generally the same in all affected members of a family.
Normal values for FVIII and FIX can range between 50 and 150 percent of the mean value, while severely affected individuals generally have levels of less than or equal to 1 percent, moderately affected persons 1 to 5 percent, and mildly affected persons 5 to 35 percent. Severely affected individuals often have spontaneous joint and muscle hemorrhages, whereas mildly affected persons bleed only with trauma or surgery.
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