IgG4, Immunoglobulin Subclasses, Serum

Casandra

Casandra Test Code MC71352Version 1 (DRAFT)

Performing Lab

Lab Mayo Clinic LabLab Test ID IGGS4CPT Code 82787

IgG4, Immunoglobulin Subclasses, Serum

Clinical Use

Use

The IgG4, Immunoglobulin Subclasses, Serum test is primarily used to support the diagnosis of IgG4-related disease. IgG4-related disease is a systemic inflammatory condition that can affect multiple organ systems, presenting with tumor-like swelling and infiltration by IgG4-positive plasma cells. Elevated serum concentrations of IgG4 are found in a significant number of patients diagnosed with this disease, which includes conditions like autoimmune pancreatitis, Mikulicz disease, sclerosing sialadenitis, and several others. Measuring serum IgG4 can be a crucial part of the diagnostic process, often in conjunction with tissue biopsy and clinical assessment.

Special Instructions

This test specifically measures the IgG4 protein subclass. If measurement of all IgG subclasses is needed, the IGGS test should be ordered instead. Patients are recommended to fast for 12 hours prior to collection, though it is not a mandatory requirement. The preferred collection container is a serum gel tube, but a red top tube is also acceptable. The serum must be centrifuged and aliquoted into a plastic vial for submission.

Limitations

While elevated levels of IgG4 in the serum can support a diagnosis of IgG4-related disease, they are not exclusively indicative of it. Increased IgG4 levels can also be associated with other conditions such as multicentric Castleman disease, allergic disorders, Churg-Strauss syndrome, and sarcoidosis. Additionally, undetected antigen excess is rare but possible, meaning results need to be considered alongside other clinical and laboratory findings to ensure accurate diagnosis and treatment.

Test Details

FDA Approved