What is CMV IgM?
When a person is exposed to the cytomegalovirus and contracts an infection the body produces an antibody cytomegalovirus immunoglobulin M, in response to it. Cytomegalovirus belongs to the family of herpes virus and can affect individuals of any age. This virus is usually asymptomatic in healthy individuals but is extremely lethal for newborns, pregnant women and individuals with a compromised immune system. The IgM antibodies are produced as an early immune response and appear in the first or second week of the infection. The antibodies can be detected for several months, then their levels start to decline and the IgG antibodies become more prominent to provide long-term immunity.
A CMV IgM antibody test is conducted for the measurement of the CMV IgM bodies to detect the presence of an active infection. Positive result suggests that the person has an ongoing or a recent infection. Further testing is suggested by the healthcare provider for the confirmation of the stage of the infection.
How is the Test Performed?
CMV IgM test is a simple blood test with no associated risks, although, some people may experience slight discomfort while drawing the blood.
Preparation
- No special preparation is required for the test.
- Inform your healthcare provider about the medications you are taking, had any recent infection, or got a vaccine.
Collection
- The collection is simple involving the blood drawn from the vein and sent to the laboratory for further analysis.
Laboratory Analysis
- The sample is then analyzed in the laboratory using techniques such as Enzyme-Linked Immunosorbent assay (ELISA) and chemiluminescence immunoassay (CLIA).
What are the symptoms that prompt this test?
The healthcare provider may recommend this test if an individual is showing symptoms of acute CMV infection particularly if they are pregnant or immunocompromised;
General Symptoms
- Unexplained fever followed by chills
- Sore throat
- Swollen lymph nodes
- Fatigue
- Extreme weakness
- Appetite loss
- Headache
What are Normal Ranges for This Test?
The CMV IgM test results are given as positive or negative. Positive indicating the presence of virus whereas negative result is indicative of no infection. The generally accepted reference ranges are given in arbitrary units (AU);
Negative – Less than 0.9 AU
Equivocal – 9 to 1.1 AU
Positive – More than 1.1 AU
**The reference ranges given above are for general guidance only and may vary between the laboratories according to the assay of the test.**
What Happens if Test Results Show Abnormal Levels?
If the CMV IgM test results comes out to be positive the healthcare provider warrants further testing such as CMV IgG avidity testing and Polymerase Chain Reaction (PCR). Mostly the infection goes away on its own however in high-risk individuals the doctor starts an early treatment including the antibiotic medications, commonly these antibiotics are recommended;
- Ganciclovir and valganciclovir in severe infections
- Foscarnet and cidofovir for resistant CMV infection
In pregnant women the specialist ensures regular monitoring and consultation for the assessment of the potential risks to the baby.
