Selective Antibody Deficiency With Normal Immunoglobulins (SADNI) By James Fernandez, MD, PhD, Cleveland Clinic Lerner College of Medicine at Case Western Reserve University Reviewed / Revised Jan 2023 View Patient Education Diagnosis Treatment Selective antibody deficiency with normal immunoglobulins (Ig) is characterized by deficient specific antibody response to polysaccharide antigens but not to protein antigens, despite normal or near normal serum levels of immunoglobulins, including IgG subclasses.