When is it necessary to treat a patient with low immunoglobulin levels? — Barbara B. Rogers, CRNP, MN, AOCN, ANP-BC, Philadelphia, PA

Typically, starting IVIG replacement therapy for low immunoglobulin level correction is considered necessary when levels of IgG are less than 200 mg/dL. To provide constant protective levels, the monthly dose should be adequate to maintain a trough (measured immediately prior to the next treatment) of greater than 200 mg/dL. IVIG therapy can be justified for IgG levels greater than 200 mg/dL in patients with a significant infectious disease history and reduced IgG subtypes, such as IgG3.— Donald Fleming, MD