Parvovirus B19

Indications for Testing

In most patients, clinical presentation is adequate for diagnosis
Typical presentation in pregnant females – either rash or arthritis
Development of aplastic anemia in immunocompromised patient

Laboratory Testing

Antibody testing
- B19 IgM and IgG antibodies may remain negative in immunocompromised patients or patients presenting with transient aplastic crisis
- By the time rash or polyarthropathy occurs in immunocompetent patients, viremia is usually cleared and serum antibodies can be used to confirm the clinical diagnosis
- Appearance of an IgM antibody response normally occurs 7-14 days after the onset of disease
  - IgM antibodies remain detectable 2-3 months after infection
- Past infection documented by IgG antibodies – IgG antibodies remain detectable for life
PCR testing
- More sensitive than antibody testing
- In serum samples, positive result indicates ongoing acute or persistent infection
- In bone marrow samples, positive result indicates acute or remote infection
Confirmation of parvovirus infection in pregnancy mandates followup with testing of fetus for development of hemolytic disease

Differential Diagnosis

Hydrops fetalis
- Rh incompatibility
- Chromosomal abnormality (Turner syndrome, Down syndrome, trisomy 18)
- TORCH syndrome
- Hereditary hemolytic disease
Rash
- Scarlet fever
- Rubella virus
- Roseola
- Varicella-zoster virus
Arthritis

Parvovirus B19 is a member of the Erythrovirus family, so named because of its tropism for erythroid precursor cells.

Epidemiology

Prevalence
- 15% of preschool children – seropositive
- 50% of young adults – seropositive
- 85% of elderly – seropositive
Incidence – peak in late winter, early spring
Age – peak is 5-15 years
Transmission
- Respiratory droplets
- Blood products

Organism

Small, single-stranded DNA virus
Lacks lipid envelope – resistant to heat and detergent inactivation
Targets rapidly growing erythroid progenitor cells

Risk Factors

Immunodeficiency disorder
Pregnancy

Clinical Presentation

Many parvovirus infections asymptomatic – particularly in children
Erythema infectiosum (EI) or fifth disease
- Classically presents in school-aged children
- EI is a benign, self-limited, febrile illness associated with a slapped cheek appearance on the face and a lacy or reticular rash on the trunk and limbs
Severe anemia is the major complication due to the virus's predilection for red-cell precursors in the bone marrow
- May cause aplastic crisis or persistent chronic anemia in immunocompromised patients
Migratory polyarthropathy may occur in up to 50% of adults – particularly females
- Generally resolves within a few weeks
- May persist for years (rare)
Pregnant females – abortion or stillbirth due to hydrops fetalis
- Risk of transplacental infection – ~30%
- Risk of fetal loss, predominantly in the early 2nd trimester – ~9%
- Represents 10-20% of all cases of nonimmune hydrops
- Congenital infections (primarily diagnosed by ultrasound)
  - Fetal risk greatest in 1st trimester; decreased in 2nd and 3rd trimesters
Associated with the onset of autoimmune disorders
- Systemic lupus erythematosus
- Rheumatoid arthritis
- Systemic vasculitides
- Autoimmune thrombocytopenia
- Hemolytic anemia
Transient aplastic crisis may result in patients with increased erythropoiesis (hemoglobin disorders, hemoglobinopathies)
Chronic bone marrow failure and pure red-cell aplasia (PRCA) – may become persistent in patients unable to mount efficient immune response
- PRCA or chronic anemia may result

Treatment

Treatment is symptomatic
Prophylactic immunoglobulin can be used in pregnant and immunocompromised patients
Weekly monitoring in utero for hemolysis required in parvo-exposed pregnant women

Tests generally appear in the order most useful for common clinical situations

Test name: Parvovirus B19 Antibodies, IgG and IgM

ARUP #: 0065120

Methodology: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Use:

Confirm infectious agent as parvovirus

Provide differential diagnosis for clinically significant chronic anemia in immunocompromised patients

Provide differential diagnosis for abortion or stillbirth due to hydrops fetalis

Limitations:

May be negative in immunocompromised patients and patients in transient aplastic crisis (TAC)

Sensitivity 70-80%

Test name: Parvovirus B19 Antibodies Seroconversion, IgG and IgM