How to Read Rubella IgM Test Report
Rubella IgM Test:Rubella virus causes mild infection which is characterized by fever and rash that lasts for about 3 days. This test detects measures the amount of antibodies and detects their presence, mainly IgM, produced by the immune system against the virus in response to infection or immunization. Elevated levels of IgM require immediate medical attention.
Factors involved to understand the normal range of Rubella IgM levels:
- What is the normal range of Rubella IgM test?
- What does negative Rubella IgM test result mean?
- What does positive Rubella IgM test result mean?
- Symptoms of a positive Rubella IgM test
- Causes of a positive Rubella IgM test
- Precautions to be taken to avoid infection
- Are there any risks associated with Rubella IgM test?
- What other tests are ordered along with Rubella IgM test?
What is the normal range of Rubella IgM test?
The absence of Rubella IgM antibodies in the blood is the normal range of the test.
What does negative Rubella IgM test result mean?
Absence of Rubella IgM antibodies in the blood indicates that the person has not been exposed to the rubella virus or vaccination and does not have immunity against it.
Positive IgG and negative IgM test result indicates a patient has been previously exposed to the virus and vaccination and has immunity against it.
What does positive Rubella IgM test result mean?
Presence of IgM antibodies against rubella suggests an active infection or previous exposure to rubella. Positive IgM and negative IgG indicates a recent infection. Positive IgM in newborn babies are an indication of congenital infection or recent post-natal infection.
Since, several factors can interfere with the test and give false positive results, doctor may order an IgG test to confirm the diagnosis and look for an increase in the amount present.
The optimum time-point for collection of serum is five days after the onset of symptoms (fever and rash) when >90% of cases will be IgM positive. If serum collected less than five days after onset is negative, a second sample would be necessary to confirm/rule out rubella.
Symptoms of a positive Rubella IgM test
Rubella infection is usually mild with less noticeable symptoms. In cases where symptoms are observed, they include:
- Low grade fever
- Headache
- Redness or swelling in the eye
- General discomfort
- Swollen or enlarged lymph nodes
- Cough
- Runny nose
- Aching joints
- Maculopapular Rash which starts from face and spreads all over the body.
Causes of a positive Rubella IgM test
Rubella test can give false positive results for the presence of IgM antibodies due to infection with other viruses. The test is also positive when a person having a rash illness due to other reasons is screened for measles or rubella IgM. Cross reaction of components with other proteins in the body may also give false positive IgM results or non-specific positive results for the test.
False positive result for Rubella infection can occur due to infection with other viruses such as Cytomegalovirus, Epstein-Barr Virus (EBV), infectious mononucleosis, parvovirus infection, and rheumatoid factor (RF).
In cases of positive results, IgM testing is repeated 5-10 days later to check for significant increase in the titer to confirm the diagnosis of rubella infection.
Precautions to be taken to avoid infection
Rubella infection can be prevented through immunization with vaccines. The rubella vaccine is a part of the combination vaccine called MMR, which stands for Measles, Mumps, and Rubella. It is recommended that children should receive two doses of MMR, first at the age of 12-15 months and second dose at the age of 4-6 years.
Woman receiving MMR vaccine should avoid getting pregnant for at least a month after the vaccine is administered. This can help avoid complications in the baby caused by rubella virus. Children having rubella infection should avoid going to childcare, preschool, and school until the child has fully recovered from the infection. Person suspected with rubella should consult a doctor to confirm the diagnosis and avoiding any contacts to prevent the spread of infection.
Are there any risks associated with Rubella IgM test?
Blood tests involve minor chances of side effects due to having a sample taken from a vein. This may include:
- Pain, soreness, and bruising at the site of puncture
- Bleeding or hematoma
- Fainting or feeling lightheaded
- Infection at the site due to the needle used
- Pain from multiple punctures done to locate a vein
These side effects can resolve on their own.
What other tests are ordered along with Rubella IgM test?
In addition to screening for antibodies, a rubella viral culture test and detection of rubella virus by testing for genetic material using a throat swab is also recommended for confirming the diagnosis. Since, infections with other viruses can give false positive results, specific testing for those viruses is also recommended.
TORCH screen test that checks for different infections, such as Toxoplasmosis, Rubella, Cytomegalovirus, and Herpes simplex virus, is also ordered to rule in or rule out rubella diagnosis. Other tests include diagnostic tests for screening for syphilis, hepatitis B, HIV, enterovirus, Epstein-Barr virus, varicella zoster virus, etc. are also suggested. CRP test is also ordered as an additional diagnostic test. Nasal, or urine specimens for viral detection by polymerase chain reaction (PCR) testing and molecular typing are also suggested for confirmation.
Repeat testing for IgM and IgG is recommended when the initial tests are positive to confirm the diagnosis.
The test requires no special preparation. Rubella infection generally lasts for 2-3 days and resolves without treatment. Rubella is best prevented by the MMR vaccine. Once antibodies are developed against rubella virus, the person will develop immunity for the infection. It is recommended that pregnant women be tested for rubella immunity prior to or during early pregnancy.
Anti-viral medication, anti-fever medications, hydrating skin lotions, etc. are some of the treatment measures suggested to Rubella patients. Drinking plenty of fluids, eating healthy foods, and lots of rest is often recommended to help fight the infection. However, since the illness is mild, doctors generally let it run its course. Doctors often recommend isolation from others especially pregnant women during the infectious period.
