Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1439 page)

   Detection of VRE carriage may require submission of several samples, and collection from several potentially colonized sites.

   
Common pitfall:
The VRE screening culture is usually not indicated for evaluation of potentially infected material. Because only selective media is used for screening, other potential pathogens would be missed if VRE screening culture only is requested. VRE grow well in wound and other cultures submitted for evaluation of infected specimens.

VARICELLA-ZOSTER VIRUS (VZV) CULTURE (RULE OUT)

   Definition

   VZV causes chickenpox and shingles. Clinical diagnosis is usually straight-forward 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.