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Diagnosing parvovirus B19 infection
Parvovirus B19 preferentially replicates in erythroid progenitor cells.(1) Infection with parvovirus B19 occurs early in life and the virus is transmitted by respiratory secretion and occasionally by blood products. Antibody prevalence ranges from 2% to 15% in early adults.(1)
Parvovirus B19 may result in an asymptomatic infection or produce a wide spectrum of disease ranging from erythema infections (slapped cheek syndrome or fifth disease) in children to arthropathy, severe anemia, and systemic manifestations involving the central nervous system, heart, and liver depending on the immune competence of the host.(2,3) Infection with parvovirus B19 in pregnant women may cause hydrops fetalis, congenital anemia, abortion, or stillbirth of the fetus.(4) Parvovirus B19 is also the causative agent of persistent anemia usually, but not exclusively, in immunocompromised patients, transplant patients, and infants.
Most acute infections with parvovirus B19 are diagnosed in the laboratory by serologically detecting IgG and IgM class antibodies with enzyme-linked immunosorbent assay testing.
A positive result indicates that parvovirus B19 DNA is present in the clinical sample. However, a positive result does not differentiate between actively replicating virus, transient infection that may beasymptomatic, or simply the presence of remnant viral nucleic acid.
A negative result suggests the absence of parvovirus B19 infection.
A negative result does not necessarily indicate the absence of parvovirus B19 infection. False-negative results may be due to the virus being present at levels below the limit of detection for this assay, or to inhibitory substances that may be present in the specimen.
This assay has only been validated for the detection of genotype 1 parvovirus B19 and its ability to detect the less common genotypes 2 and 3 is unknown.
The following data supports the use of this assay for clinical testing.
Accuracy/Diagnostic Sensitivity and Specificity:
Results from this real-time PCR assay on the LightCycler (LC PCR) were compared to a Centers for Disease Control and Prevention (CDC) PCR-based assay on tissue biopsy specimens of temporal artery. Using the CDC PCR as the gold standard, the diagnostic sensitivity and specificity for detection of parvovirus B19 was 97%.
To supplement the above data, 30 negative cerebrospinal fluid, body fluids, and tissues, and 45 negative blood specimens were spiked with parvovirus B19-positive control plasmid at the limit of detection (LoD)(10-20 targets/microliter). The 30 spiked specimens (45 bloods) were run in a blinded manner along with 30 negative (nonspiked) specimens (45 bloods). Results showed 97% to 100% of the spiked specimens were positive and 100% of the nonspiked specimens were negative.
The LoD of this assay is 10 to 20 targets/microliter in sample matrix.
No PCR signal was obtained with extracts of 11 viral and bacterial isolates that may cause symptoms similar to infection with parvovirus, including herpes simplex virus, varicella-zoster virus, cytomegalovirus, and human herpesvirus-6, -7, and -8.
Interassay precision was 100% and intra-assay precision was 97%.
Although the reference range is typically "negative" for this assay, it may detect viremia in asymptomatic individuals or viral nucleic acid. However, this assay is only to be used for patients with a clinical history and symptoms consistent with parvovirus B19 infection, and must be interpreted in context of clinical picture. This test is not to be used to screen asymptomatic patients.
This is a qualitative assay, and results are reported as either negative or positive for targeted parvovirus B19.
1. Heegaard ED, Brown KE: Human parvovirus B19. Clin Microbiol Ref 2002;15:485-505
2. Bultmann BD, Klingel K, Soltar K, et al: Fatal parvovirus B19 associated myocarditis clinically mimicking ischemic heart disease: an endothelial cell-mediated disease. Hum Pathol 2003;34:92-95
3. Rerolle JP, Helal I, Morelon E: Parvovirus B19 infection after renal transplantation. Nephrologie 2003;24:309-315
4. Chisaka H, Morita E, Yaegashi N: Parvovirus B19 and the pathogenesis of anaemia. Rev Med Virol 2003;16:347-359