Quantitative Immunoglobulins (IgG, IgA, IgM): When to Order, What the Patterns Mean, and the Myeloma Connection
Quantitative Immunoglobulins (IgG, IgA, IgM): When to Order, What the Patterns Mean, and the Myeloma Connection Recurrent infections, monoclonal spikes, and the difference between too much of one and not enough of everything else. The Three Immunoglobulins IgG (700–1600 mg/dL): The workhorse—75% of serum immunoglobulins. Provides long-term immunity after infection or vaccination. Crosses the placenta (maternal IgG protects the newborn). Low IgG = increased risk of bacterial infections. IgA (70–400 mg/dL): Mucosal immunity—found in saliva, tears, respiratory and GI secretions. Selective IgA deficiency is the most common primary immunodeficiency (1 in 400–800). Connects to our celiac post (IgA deficiency causes false-negative tTG-IgA). IgM (40–230 mg/dL): The first responder—the initial antibody produced during acute infection. Elevated IgM on infection-specific testing = acute/recent infection. Also the antibody class in Waldenström's macroglobulinemia. When to Order Qu...