Guidelines
Investigation and Diagnosis
Urgent testing for:
- Prvovirus B19-specific serology (IgM and IgG)
- If parvovirus B10-specific IgM is detected → suggest recent infection
- Confirm diagnosis with high-titre viral DNA PCR or parvovirus B19-specific IgG
- Rubella serology (irrespective of any previous testing or immunisation status)
The above is a simplified version (sufficient for exams), see below for full guidance. As the approach differ slightly depending on whether it is suspected infection of exposure to the virus.
Suspected Parvovirus B19 Infection
Order urgent parvovirus B19-specific IgM
- -ve IgM → excludes infection in the 4 weeks prior blood test
- Note if the test is taken >4 weeks after rash onset / illness → unable to exclude infection, seek specialist advice
- +ve IgM → suggest recent infection → confirm diagnosis with high-titre viral DNA PCR or parvovirus B19-specific IgG
Urgent testing for rubella should also be arranged (irrespective of any previous testing or immunisation status).
Possible Exposure to Parvovirus B19 Infection
Order urgent parvovirus B19-specific IgG and IgM
| Test result | Interpretation | Subsequent Action |
|---|---|---|
| -ve IgM and +ve IgG | Past infection, no recent infection | Re-testing not necessary |
| +ve IgM (irrespective of IgG result) | Suggest recent infection | Confirm diagnosis with antenatal booking blood sample / repeat blood test after 7-10 days |
| -ve IgM and -ve IgG | Susceptible to infection | Repeat blood test 1 month after last contact (even if asymptomatic or earlier if symptoms develop) |
Urgent testing for rubella should also be arranged (irrespective of any previous testing or immunisation status).
Management (confirmed infection)
Urgent referral to fetal medicine specialist for:
- Serial fetal ultrasound scans and Doppler (to detect fetal anaemia, heart failure and hydrops)
If there is suspected fetal hydrops:
- Amniotic fluid sample for parvovirus B19 virus DNA detection
- Fetal blood sampling + intrauterine RBC transfusion may reduce fetal mortality rate