Antibody immunodeficiency disorders — such as multiple myeloma, HIV infection, solid organ tumors, or chronic liver disease — are a spectrum of diseases characterized by decreased immunoglobulin levels. Disease states can range from deficiency of a single class or subclass to the complete absence of all classes of immunoglobulin. xMAP® Technology is of great help in the shedding light on these disorders, as it enables simultaneous quantification of immunoglobulin isotypes. Using xMAP Technology helps reduce the number of tests that must be performed and eliminates the potential for inaccurate results due to the inherent variability of multiple, separate tests.