Monday, August 15, 2011

Parvovirus B19 Laboratory diagnosis

• Serology
IgM directed against parvovirus B19 can be detected 10 - 12 days after infection and is a convenient marker for recent or ongoing infection. The most sensitive methods use the capture technique in RIA or ELISA. Testing for IgG is useful for seroprevalence studies but is not helpful in diagnosing acute infection because it simply indicates past exposure to virus (Brown and Young, 1997).
• Molecular detection
Detection usually relies on presence of the viral genome. During acute uncomplicated infections in immunocompetent patients, B19 DNA is only detectable for 2 to 4 days by dot-blot hybridization. The sensitivity of B19 DNA detection has been greatly increased by the use of PCR. However, confusing results can be a problem in diagnosing acute disease because of the ease of contamination, long-term persistence of low levels of virus in uncomplicated infections, and false-positive results. Because of these issues, DNA hybridization is more certain than PCR (Abkowitz et al., 1997).
DNA can also be detected by in situ hybridization of tissues (Morey et al., 1992), but this is not a useful routine screening test. In the event of B19 infection or seroconversion during pregnancy, hydrops can be detected by ultrasound and fetal infection determined by PCR (Torok et al., 1992).

No comments: