Immunoglobulin M (IgM)

Test Code

IGM

Alias/See Also

Epic: LAB72

Preferred Specimen

Specimen Type: Serum
Collection Container: Serum gel
Specimen Volume: 3 mL

Minimum Volume

0.25 mL

Other Acceptable Specimens

Collection Container: Red top

Instructions

Centrifuge and separate cells after clot formation and within 4 hours of collection.

Transport Container

Plastic vial

Specimen Stability

Room temperature: 2 months
Refrigerated: 4months
Frozen: 6 months

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Unlabeled, mislabeled, wrong tube type, hemolyzed, visually lipemic, QNS, exceeds specimen stability requirements.

Methodology

Immunoturbidimetric

Setup Schedule

Daily

Report Available

Same day

Limitations

Samples containing paraproteins (abnormal monoclonal antibodies) may incorrectly fall within the reference range. Samples with elevated total protein concentrations or suspected paraproteinemia can be screened with other methods such as electrophoresis. Turbidity and particles in samples can interfere with the assay. Therefore, particulate matter should be removed by centrifugation prior to running the assay.
Hemolysis in excess of 250 mg/dL will falsely decrease serum IgM
Bilirubin up to 60 mg/dL has no effect
Triglycerides up to 1000 mg/dL will not affect the accurate measurement of serum IgM. Triglycerides in excess of 1000 mg/dL has not been evaluated.

Reference Range

Newborn: 6 - 21 mg/dL
3 months - 1 year: 17 - 150 mg/dL
1 - 12 years: 41 - 240 mg/dL
>12 years: 22 - 293 mg/dL

Clinical Significance

IgM, primarily present as a pentamer, is the first immunoglobulin class produced during an initial immune response and antigen-IgM complexes actively fix complement. The large molecular size of the pentamer enables direct cross-linking and agglutination of particulate and cellular antigens. Because IgM is involved in primary immune response, presence of IgM is useful in assessing whether a particular infection is acute (IgM present) or chronic (IgG predominate class present). Additionally, IgM is the first immunoglobulin class to be synthesized by a fetus or newborn. IgM antibodies do not cross the placenta. Polyclonal IgM increases may indicate a viral infection, such as viral hepatitis or infectious mononucleosis, or the early response to bacterial or parasitic infection. Elevated levels are also seen with hyper-IgM dysgammaglobulinemia, active sarcoidosis, collagen vascular disease, and nephrotic syndrome. Monoclonal IgM increases are seen in Waldenstrom’s macroglobulinemia, malignant lymphoma, reticulosis, and cold agglutinin hemolysis disease. Small IgM monoclonal bands can accompany a variety of neoplasms, particularly of the GI tract. Decreased IgM levels are usually not due to primary IgM deficiency. Secondary IgM deficiency may be associated with IgA, or IgG type multiple myeloma, protein-losing enteropathies, burns, or immunosuppressive therapy. IgM deficiency is associated with increased, recurrent infections.

Performing Laboratory

Inova Laboratories

2832 Juniper Street

Fairfax, VA 22031

Last Updated: April 11, 2023
Last Review: N. Wolford, April 11, 2023

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.