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Varicella-Zoster Virus (VZV) Culture (Rule out)


Definition


  • VZV causes chickenpox and shingles. Clinical diagnosis is usually straightforward for these infections. Occasionally, specific diagnosis may be needed for unusual, serious infections, including disseminated disease, or infections in pregnant, immunocompromised, and other high-risk patients.

Special Collection and Transport Instructions


  • General recommendations for viral culture apply. Specimens should be collected early in acute infection. Specimens from cutaneous or mucous membranes are most commonly submitted. Samples should be taken from fresh, wet lesions, ideally from intact vesicles after unroofing. Most specimens should be placed in a viral transport medium and transported on wet ice (4 ‚ °C).

Use


  • This test may be used to isolate VZV when specific diagnosis is required. Patient specimens are usually inoculated onto human lung fibroblast cell cultures, like WI-38. Cell morphology is monitored; cultures showing cytopathic effect typical for VZV should be confirmed using specific immunologic techniques, like staining with tagged monoclonal anti-VZV antibodies.
  • Turnaround time: Up to 4 weeks. Most positive cultures are detected within 7 days.

Interpretation


  • Expected results: Negative.
    • Positive result: Cell cultures positive for VZV indicate active infection.
    • Negative result: Negative cell cultures decrease the likelihood of VZV infection, but cannot absolutely rule out VZV infection, especially for CSF and mucosal surface samples.

Limitations


  • There may be poor sensitivity for certain specimen types.
  • Turnaround time for VZV culture may be prolonged, limiting their utility for acute management of critically ill patients.
  • Common pitfall: Collection of specimens from dried, overcrusted lesions.
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