What are the other Names for this Test? (Equivalent Terms)
- Parvo B19 Test
- Parvovirus Test
What is Parvovirus B19 Test? (Background Information)
- Parvovirus B19 causes a disease called erythema infectiosum, also known as “fifth disease”. Though it is a common childhood ailment, the test for parvovirus is only used to detect infection or exposure in those individuals prone to complications from the virus, or in pregnant women who may transmit infection to the fetus
- While in most individuals, parvovirus causes a self-limiting illness, in certain individuals, some complications may arise:
- In children, fifth disease might cause a classic “slapped- cheek” rash on both cheeks, while some adults may have joint pain and swelling, or reddishness of the hands and feet, due to “gloves and socks syndrome” (another infection also caused by parvovirus)
- Individuals with pre-existing diseases affecting the red blood cells, such as sickle cell anemia, may develop worsening of anemia with parvovirus infection
- Pregnant women may transmit infection to the fetus, which may result in anemia or myocarditis (inflammation of the heart muscle) or hydrops fetalis (swelling of the fetus, due to fluid retention). There is also a risk of miscarriage or still birth
- Immunocompromised patients, such as those affected by HIV, are prone to persistent anemia, as well
- The Parvovirus B19 Test is done to detect the presence of antibodies (proteins produced by the immune system in response to infection), or genetic material of the virus in such ‘complication-susceptible’ individuals
- Testing for antibodies (IgG and/or IgM) is done on a blood sample, while the presence of viral genetic material is detected using a blood/bone marrow/fetal cord blood/amniotic fluid sample
PCR (polymerase chain reaction) technique is used to increase copies of viral DNA that may be present in the test sample, for detection. The test for viral genetic material is particularly useful in immune deficient individuals.
What are the Clinical Indications for performing the Parvovirus B19 Test?
A physician may order Parvovirus B19 Testing in the following cases:
- Individuals with pre-existing disease affecting life span of red blood cells (such as sickle cell disease, thalassemia, etc.), if they present with symptoms suspicious of parvovirus infection (flu like symptoms, such as fever, fatigue, upset stomach, headache, etc.)
- Individuals, who have been exposed to others with parvovirus infection, and showing symptoms
- Pregnant women with symptoms suspicious of parvovirus, or following exposure to an infected individual. Testing for fetal infection may also be carried out in such instances, if warranted
- Individuals presenting with chronic anemia or arthritis, especially if they are known to be immune compromised
How is the Specimen Collected for Parvovirus B19 Test?
Sample required: Specimen sample of any of the below
- Bone marrow
- Fetal cord blood
- Amniotic fluid
- A blood sample is drawn through a needle inserted into the vein (arm)
- Bone marrow aspiration/biopsy - this procedure is performed under mild sedation, and/or local anesthesia. Commonly, the sample of cells are obtained from the hip bone (other sites include the chest bone /sternum in adults, tibia/shin bone in infants). A special biopsy needle or a needle attached to a syringe is used to obtain cell samples from the bone marrow of the hip bone. After the sample collection, the puncture site is dressed and has to be kept dry for about 48 hours
- Fetal cord blood is collected by introducing a needle into the umbilical vein (vein present in the umbilical cord) using ultrasound guidance. (A probe passes sound waves inside the body and picks up the reflected waves. This information is analyzed by a computer, to form images of the inside of the body)
- Amniotic fluid (the fluid present in the womb around the fetus) is collected by introducing a needle into the womb (procedure called amniocentesis)
Preparation required: None
What is the Significance of the Parvovirus B19 Test Result?
The possible outcomes of Parvovirus B19 Test and their significance are as follows:
- Antibody testing: Presence of both IgM and IgG antibodies indicates active or recent infection. Presence of IgM antibody alone indicates a very recent infection; presence of IgG antibody alone indicates infection in the past. A lack of antibodies indicates no prior exposure to the virus
- Test for Parvovirus B19 DNA: A positive test result is indicative of current infection; while a negative result does not conclusively rule out the infection
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
The following article link will help you understand fifth disease.
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.
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References and Information Sources used for the Article:
http://labtestsonline.org/understanding/analytes/parvo/ (accessed on 03/16/2014)