Chronic infections such as Lyme disease and autoimmune disorders are associated with circulating immune complexes: antigen( foreign protein ) bound to antibodies, immunoglobulins.
Normally these are not present in the blood. A test available only at Quest Diagnostics is available to measure this variable. The is the C3d test: CPT 86332. This should not be confused with the C3a test available at Labcorp which measures a form of complement. This parameter may be useful in following the course of the illness. If levels are elevated enzyme therapy such as Wobenzym-N may be beneficial.