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HelpTest Code LAB7502 West Nile Virus Antibody, IgG and IgM, Serum
Additional Codes
WEST NILE IGG AND IGM AB, SERUM
WNS
Useful For
Laboratory diagnosis of infection with West Nile virus using serum specimens
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| WNGS | West Nile Virus Ab, IgG, S | No | Yes |
| WNMS | West Nile Virus Ab, IgM, S | No | Yes |
| WNVSI | West Nile Serum Interpretation | No | Yes |
Method Name
Enzyme-Linked Immunosorbent Assay (ELISA)
Specimen Type
SerumSpecimen Required
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Specimen Minimum Volume
0.4 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 14 days | |
| Frozen | 14 days |
On-campus collections: Tube to 99 or deliver to University Extension Hospital Room EH318
Send in plastic vial, Refrigerated.
Off-campus collections:
Centrifuge and aliquot within 2 hours.
Specimen to be stored/transported Refrigerated
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | Reject |
| Heat Inactivated specimen | Reject |
Reference Values
IgG: negative
IgM: negative
Reference values apply to all ages.
Interpretation
The presence of IgG-class antibodies to West Nile virus (WNV) in 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 collected within approximately 7 days postinfection should be compared with a specimen collected approximately 14 to 21 days postinfection to demonstrate rising IgG antibody levels between the 2 serum specimens.
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 8-10 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 WNV infection, IgM may be detectable in cerebrospinal fluid before it becomes detectable in serum.
Method Description
IgG:
Polystyrene microwells are coated with recombinant West Nile virus (WNV) antigen. Diluted serum specimens and controls are incubated in the wells to allow specific antibody present in the specimens to react with the antigen. Nonspecific reactants are removed by washing, and peroxidase-conjugated antihuman IgG is added and reacts with specific IgG. Excess conjugate is removed by washing. Enzyme substrate and chromogen are added, and the color is allowed to develop. After adding the stop reagent, the resultant color change is quantified by a spectrophotometric reading of optical density (OD). Specimen OD readings are compared with reference cutoff readings to determine results.(Package insert: West Nile Virus IgG DxSelect. Focus Diagnostics; 05/08/2018)
IgM:
Polystyrene microwells are coated with the antihuman antibody specific for IgM (mu-chain). Diluted serum specimens and controls are incubated in the wells. The IgM present in the specimen binds to the antihuman antibody (IgM specific) in the wells. Nonspecific reactants are removed by washing. WNV antigen is then added to the wells and incubated. If anti-WNV IgM is present in the specimen, the WNV antigen binds to the anti-WNV in the well. Unbound WNV antigen is then removed by washing the well. Mouse anti-flavivirus conjugated with horseradish peroxidase (HRP) is then added to the wells and incubated. If WNV antigen has been retained in the well by the anti-flavivirus in the specimen, the mouse anti-flavivirus:HRP binds to WNV antigen in the wells. Excess conjugate is removed by washing. Enzyme substrate and chromogen are added, and the color is allowed to develop. After adding the Stop reagent, the resultant color change is quantified by a spectrophotometric reading of OD that is directly proportional to the amount of antigen-specific IgM present in the specimen. Specimen OD readings are compared with reference cutoff OD readings to determine results.(Package insert: West Nile Virus IgM Capture DxSelect. Focus Diagnostics; 05/08/2018)
Day(s) Performed
Monday, Wednesday, Friday
Report Available
Same day/1 to 4 daysSpecimen Retention Time
14 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
IgG-86789
IgM-86788
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| WNS | West Nile Virus Ab, IgG and IgM, S | 94854-7 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| WNGS | West Nile Virus Ab, IgG, S | 29566-7 |
| WNMS | West Nile Virus Ab, IgM, S | 29567-5 |
| WNVSI | West Nile Serum Interpretation | 69048-7 |
Secondary ID
36769Forms
If not ordering electronically, complete, print, and send Infectious Disease Serology Test Request (T916) with the specimen.