Nurse Practitioner Chronicles

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...

  SPEP, UPEP, Immunofixation, and Free Light Chains: The Myeloma Workup NPs Need to Know The dipstick misses light chains. SPEP finds the spike. UPEP catches what spills into the urine. And free light chains changed everything. This post complements the immunoglobulin levels post and the SPEP section from the autoimmune serologic review. When you suspect a monoclonal gammopathy—whether it's MGUS, multiple myeloma, Waldenström's, or amyloidosis—you need to understand the full diagnostic panel: SPEP, UPEP, immunofixation, and serum free light chains. The Diagnostic Panel Test What It Does When to Order SPEP (Serum Protein Electrophoresis) Separates serum proteins by charge. Detects and quantifies an M-spike (monoclonal protein) in the gamma region. Suspected myeloma, MGUS screening, unexplained elevated total protein, unexplained proteinuria, polyclonal gammopathy evaluation Immunofixation (IFE) Identifies the heavy chain (IgG, IgA, IgM) and light chain (kappa or lambda) type of ...