Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (878 page)

   
Type II
(monoclonal immunoglobulin mixed with at least one other type of polyclonal immunoglobulin, most commonly IgM and polyclonal IgG; always with RF)

   Causes up to 25% of cases

   Associated most often with chronic hepatitis C virus (HCV) infection; less often with hepatitis B virus (HBV), EBV, bacterial and parasitic infections, autoimmune disorders, Sjögren syndrome, syndrome of essential mixed cryoglobulinemia, immune complex nephritis (e.g., membranoproliferative GN, vasculitis)

   High titer RF without definite rheumatic disease

   C4 levels decreased

   
Type III
(mixed polyclonal immunoglobulin, most commonly IgM–IgG combinations, usually with RF)

   Causes approximately 50% of cases

   Most commonly associated with lymphoproliferative disorders, connective tissue diseases (e.g., SLE), and persistent infections (e.g., HCV)

   
Normal range:

   Usually present in small amounts (<1 mg/dL serum) in normal persons.

   If positive, immunotyping of the cryoprecipitate is performed.

   Use

   To assist in diagnosis of neoplastic diseases, acute and chronic infections, and collagen diseases