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Test Code IGM Immunoglobulin M (IgM)

Additional Codes

Epic: LAB72

Specimen Required

Specimen Type: Serum

Collection Container/Type

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 3 mL

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

Specimen Minimum Volume

0.25 mL

Specimen Stability

Room temperature: 2 months

Refrigerated: 4months

Frozen: 6 months

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

Rejection Due To

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

Report Available

Same day / 1 day

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..

Method Name



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.

Day(s) Performed