Erythema Infectiosum Workup

Updated: Mar 06, 2020
  • Author: Glenn L Zellman, MD; Chief Editor: Dirk M Elston, MD  more...
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Approach Considerations

The diagnosis of erythema infectiosum usually is based on clinical presentation alone, and a workup for patients with the classic presentation is not necessary. For patients with other signs or symptoms associated with human parvovirus (PV) B19 or for exposure in a woman who is pregnant, confirmation of infection may be helpful and can be accomplished with the following specialized tests [5, 6, 7] :

  • IgM assays - Enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA)

  • Dot blot hybridization

  • Polymerase chain reaction (PCR) assay

  • Loop-mediated isothermal amplification

Consider determination of the complete blood count (CBC) and serologic testing in the presence of coexisting hemolytic disease, pregnancy, or arthropathy. Human PV-B19 does not grow in standard blood or tissue culture systems.

In infected pregnant patients, maternal alpha-fetoprotein levels and serial ultrasonography followed through the pregnancy may help to predict complications.

Effective noninvasive testing for PV-B19 using quantitative PCR to analyze oral fluid from swabs is currently under development. [50]

Histologic findings

Skin biopsy does not aid in diagnosis, but it may reveal nonspecific changes, including mild basilar vacuolation, dyskeratotic cells, and a sparse perivascular infiltrate.


RIA and/or ELISA

Antibody testing is most commonly performed with RIA and/or ELISA. IgM antibody, which always indicates acute infection, is usually detectable within 3 days of symptom onset. The level peaks at about 3 weeks. IgG antibody confirms previous infection and is observed 2-3 weeks after exposure; it persists for life.

Antibody testing usually is available only through commercial reference laboratories or state health and research laboratories. These tests are unreliable for diagnosing infection in immunosuppressed patients.