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25425 West Nile Virus Antibody, IgG & IgM (WNS)

West Nile Virus Antibody, IgG & IgM (WNS)
Test Code: WNVSO
Synonyms/Keywords
Arbovirus, Flavivirus, Mosquito borne encephalitis, Viral encephalitis, West Nile virus (WNV)
Test Components

​West Nile Virus Antibody IgG

West NIle Virus Antibody IgM

WNS Interpretation

Useful For
Laboratory diagnosis of infection with West Nile virus in serum specimens.
Specimen Requirements
Fasting Required Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
​No ​Serum ​Red Top Tube (RTT) ​Serum Separator Tube (SST) ​0.5 mL ​0.4 mL
Specimen Stability Information
Specimen Type Temperature Time
​Serum ​ ​Refrigerated (preferred) ​14 days
​Frozen ​14 days
Rejection Criteria
​Gross Hemolysis

​Gross Lipemia

​Gross Icterus
​Heat Inactivated specimens
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Mayo Clinic Laboratories​

​Monday, Wednesday, Friday

​1 day ​Enzyme-Linked Immunosorbent Assay (ELISA)
Reference Lab
Reference Range Information
Performing Location Reference Range
​Mayo Clinic Laboratories

​IgG: Negative
IgM: Negative

Reference values apply to all ages.

Interpretation

IgG: Presence of specific IgG class antibodies in a serum indicates infection with WNV at some time in the past. By 3 weeks postinfection, virtually all infected persons should have developed IgG antibodies to WNV. If acute-phase infection is suspected, serum specimens drawn within approximately 7 days postinfection should be compared with a specimen drawn approximately 14 to 21 days postinfection to demonstrate rising IgG antibody levels between the 2 serum specimens.

IgM: Presence of specific IgM class antibodies in a serum specimen is consistent with acute-phase infection with WNV. By the 8th day of illness, most infected persons will have detectable serum IgM antibody to WNV; in most cases it will be detectable for at least 1 to 2 months following disease resolution and in some cases will be detectable for 12 months or longer.

The absence of IgM antibodies to WNV is consistent with lack of acute-phase infection with this virus. Specimens collected too early in the acute phase (eg, before 8 to 10 days postinfection) may be negative for IgM-specific antibodies to WNV. If WNV is suspected, a second specimen collected approximately 14 days postinfection should be tested.

In the very early stages of acute WNV infection, IgM may be detectable in CSF before it becomes detectable in serum.

Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
​86788 ​1 ​WNV, IgM
​86789 ​1 ​WNV, IgG
Synonyms/Keywords
Arbovirus, Flavivirus, Mosquito borne encephalitis, Viral encephalitis, West Nile virus (WNV)
Test Components

​West Nile Virus Antibody IgG

West NIle Virus Antibody IgM

WNS Interpretation

Ordering Applications
Ordering Application Description
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Fasting Required Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
​No ​Serum ​Red Top Tube (RTT) ​Serum Separator Tube (SST) ​0.5 mL ​0.4 mL
Specimen Stability Information
Specimen Type Temperature Time
​Serum ​ ​Refrigerated (preferred) ​14 days
​Frozen ​14 days
Rejection Criteria
​Gross Hemolysis

​Gross Lipemia

​Gross Icterus
​Heat Inactivated specimens
Useful For
Laboratory diagnosis of infection with West Nile virus in serum specimens.
Test Components

​West Nile Virus Antibody IgG

West NIle Virus Antibody IgM

WNS Interpretation

Reference Range Information
Performing Location Reference Range
​Mayo Clinic Laboratories

​IgG: Negative
IgM: Negative

Reference values apply to all ages.

Interpretation

IgG: Presence of specific IgG class antibodies in a serum indicates infection with WNV at some time in the past. By 3 weeks postinfection, virtually all infected persons should have developed IgG antibodies to WNV. If acute-phase infection is suspected, serum specimens drawn within approximately 7 days postinfection should be compared with a specimen drawn approximately 14 to 21 days postinfection to demonstrate rising IgG antibody levels between the 2 serum specimens.

IgM: Presence of specific IgM class antibodies in a serum specimen is consistent with acute-phase infection with WNV. By the 8th day of illness, most infected persons will have detectable serum IgM antibody to WNV; in most cases it will be detectable for at least 1 to 2 months following disease resolution and in some cases will be detectable for 12 months or longer.

The absence of IgM antibodies to WNV is consistent with lack of acute-phase infection with this virus. Specimens collected too early in the acute phase (eg, before 8 to 10 days postinfection) may be negative for IgM-specific antibodies to WNV. If WNV is suspected, a second specimen collected approximately 14 days postinfection should be tested.

In the very early stages of acute WNV infection, IgM may be detectable in CSF before it becomes detectable in serum.

For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Mayo Clinic Laboratories​

​Monday, Wednesday, Friday

​1 day ​Enzyme-Linked Immunosorbent Assay (ELISA)
Reference Lab
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
​86788 ​1 ​WNV, IgM
​86789 ​1 ​WNV, IgG
For most current information refer to the Marshfield Laboratory online reference manual.