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Test ID: VZGM    
Varicella-Zoster Antibody, IgM and IgG (Separate Determinations), Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Laboratory diagnosis of acute/recent infection with varicella-zoster virus (VZV)

 

Determination of immune status of individuals to the VZV

 

Documentation of previous infection with VZV in an individual without a previous record of immunization to VZV

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Varicella-zoster virus (VZV), a herpesvirus, causes 2 distinct exanthematous (rash-associated) diseases: chickenpox (varicella) and shingles (herpes zoster). Chickenpox is a highly contagious, though typically benign disease, usually contracted during childhood. Chickenpox is characterized by a dermal vesiculopustular rash that develops in successive crops approximately 10 to 21 days following exposure.(1) Although primary infection with VZV results in immunity and protection from subsequent infection, VZV remains latent within sensory dorsal root ganglia and upon reactivation, manifests as herpes zoster or shingles. During reactivation, the virus migrates along neural pathways to the skin, producing a unilateral rash, usually limited to a single dermatome. Shingles is an extremely painful condition typically occurring in older nonimmune adults or those with waning immunity to VZV and in patients with impaired cellular immunity.(2)

 

Individuals at risk for severe complications following primary VZV infection include pregnant women, in whom the virus may spread through the placenta to the fetus, causing congenital disease in the infant. Additionally, immunosuppressed patients are at risk for developing severe VZV-related complications, which include cutaneous disseminated disease and visceral organ involvement.(2,3)  

 

Serologic screening for IgG-class antibodies to VZV will aid in identifying nonimmune individuals. The presence of IgM-class antibodies to VZV is suggestive of acute or recent infection however results should be correlated with clinical presentation.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

IgM

Negative (reported as negative or positive)

 

IgG

Vaccinated: positive (> or =1.1 AI)

Unvaccinated: negative (< or =0.8 AI)

Interpretation Provides information to assist in interpretation of the test results

A positive IgG result coupled with a positive IgM result suggests recent infection with varicella-zoster virus (VZV). This result should not be used alone to diagnose VZV infection and should be interpreted in the context of clinical presentation.

 

A positive IgG result coupled with a negative IgM result indicates previous vaccination to or infection with VZV. These individuals are considered to have protective immunity to reinfection.

 

A negative IgG result coupled with a negative IgM result indicates the absence of prior exposure to VZV and nonimmunity. However, a negative result does not rule out a VZV infection. The specimen may have been drawn before the appearance of detectable antibodies. Negative results in suspected early VZV infections should be followed by testing a new serum specimen in 2 to 3 weeks.

 

Equivocal results should be followed up with testing of a new serum specimen within 10 to 14 days.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Results from cord blood, neonates, or immunocompromised individuals should be interpreted with caution.

 

Testing for IgM-class antibodies to varicella-zoster virus (VZV) should be limited to patients with a clinically compatible disease.

 

The performance characteristics with individuals vaccinated with the VZV OKA strain have not been established.

 

Up to one-third of individuals with primary herpes simplex virus (HSV) infections who have experienced prior VZV infection show a heterotypic antibody response to VZV antigen making a differential diagnosis between VZV and HSV difficult in the absence of clear-cut clinical findings.

 

IgG-class antibodies to VZV may be present in serum specimens from individuals who have received blood products within the past several months, but have not been immunized or experienced past infection with this virus.

 

Serum specimens drawn early during acute phase of infection or soon after vaccination may be negative for IgM- or IgG-class antibodies to this virus, respectively.

Supportive Data

IgG:

To evaluate the accuracy of the BioPlex Varicella-Zoster Virus (VZV) IgG multiplex flow immunoassay (MFI), 500 prospective serum specimens were analyzed in a blinded fashion by the Diamedix VZV IgG EIA (Diamedix, Miami, FL) and the BioPlex VZV IgG assay. Specimens with discordant results after initial testing were repeated by both assays during the same freeze/thaw cycle. Further discrepancies were evaluated by the SeraQuest VZV IgG EIA (Quest Int, Doral, FL). The results are summarized below:

 

 

Diamedix VZV IgG EIA

BioPlex VZV IgG

 

Positive        

Negative

Equivocal

Positive

436

0

0

Negative

18(a)

22

4

Equivocal

19

0

1

 

(a) All 18 specimens tested positive by the SeraQuest VZV IgG EIA.

Sensitivity: 92.2% (436/473); 95% Confidence Interval (95% CI): 89.4%-94.3%

Specificity: 100.0 (22/22); 95% CI: 82.5%-100.0%

Overall percent agreement: 91.8% (459/500); 95% CI: 89.0%-93.9%

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Yankowitz J, Grose C: Congenital infections. In Essentials of Diagnostic Virology. Edited by GA Storch. Churchill Livingstone, New York, 2000, pp 187-201

2. Gnann JW, Whitley RJ: Herpes Zoster. N Engl J Med 2002;347:340-346

3. Cvjetkovic D, Jovanovic J, Hrnjakovic-Cvjetkovic I, et al: Reactivation of herpes zoster infection by varicella-zoster virus. Med Pregl 1999;52(3):125-128