Western Equine Encephalitis Antibody, IgG and IgM, Serum
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Aiding the diagnosis of Western equine encephalitis
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
Immunofluorescence Assay (IFA)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
West Equine Enceph Ab,IgG and IgM,S
Alphavirus (Old Arbovirus, Group A)
WEE (Western Equine Encephalitis)
WEE (Western Equine Encephalitis)
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Preferred: Red top
Acceptable: Serum gel
Specimen Volume: 0.5 mL
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Mild OK; Gross reject
Mild OK; Gross reject
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Serum||Refrigerated (preferred)||14 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The virus that causes western equine encephalitis (WEE) is widely distributed throughout the United States and Canada; disease occurs almost exclusively in the western states and Canadian provinces. The relative absence of the disease in the eastern United States probably reflects a paucity of the vector mosquito species, Culex tarsalis, and possibly a lower pathogenicity of local virus strains. The disease usually begins suddenly with malaise, fever, and headache, often with nausea and vomiting. Vertigo, photophobia, sore throat, respiratory symptoms, abdominal pain, and myalgia are also common. Over a few days, the headache intensifies; drowsiness and restlessness may merge into a coma in severe cases. In infants and children, the onset may be more abrupt than for adults. WEE should be suspected in any case of febrile central nervous system disease from an endemic area. Infants are highly susceptible to central nervous system disease and about 20% of cases are under 1 year of age. There is an excess of males with WEE clinical encephalitis, averaging about twice the number of infections detected in females. After recovery from acute disease, patients may require from several months to 2 years to overcome the fatigue, headache, and irritability. Infants and children are at higher risk of permanent brain damage after recovery than adults.
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.
In patients infected with this virus, IgG antibody is generally detectable within 1 to 3 weeks of onset, peaking within 1 to 2 months, and declining slowly thereafter.
IgM class antibody is also reliably detected within 1 to 3 weeks of onset, peaking and rapidly declining within 3 months.
Single serum specimen IgG > or =1:10 indicates exposure to the virus.
Results from a single serum specimen can differentiate early (acute) infection from past infection with immunity if IgM is positive (suggests acute infection).
A 4-fold or greater rise in IgG antibody titer in acute and convalescent sera indicate recent infection.
In the United States it is unusual for any patient to show positive reactions to more than 1 of the arboviral antigens, although Eastern equine encephalitis (WEE) and eastern equine encephalitis (EEE) antigens will show a noticeable cross-reactivity.
Infections with arboviruses can occur at any age. The age distribution depends on the degree of exposure to the particular transmitting arthropod relating to age and sex, as well as the occupational, vocational, and recreational habits of the individuals. Once humans have been infected, the severity of the host response may be influenced by age: WEE tends to produce the most severe clinical infections in young persons. Infection in males is primarily due to working conditions and sports activity taking place where the vector is present.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
All results must be correlated with the clinical history and other data available to the attending physician.
Specimens drawn within the first 2 weeks after onset are variably negative for IgG antibody and should not be used to exclude the diagnosis of arboviral disease. If arboviral infection is suspected, a second specimen should be drawn and tested 10 to 21 days later.
Since cross-reactivity with dengue fever virus does occur with St. Louis encephalitis (SLE) antigens and, therefore, cannot be differentiated further. The specific virus responsible for such a titer may be deduced by the travel history of the patient, along with available medical and epidemiological data, unless the virus can be isolated.
Eastern equine encephalitis and Western equine encephalitis viruses show some cross-reactivity; however, antibody response to the infecting virus is typically at least 8-fold higher.
Usually, when an infection with an arbovirus is suspected, it is too late to isolate the virus or draw serum specimens to detect a rise of antibody titer.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Gonzalez-Scarano F, Nathanson N: Bunyaviruses. In Fields Virology. Vol 1. 2nd edition. Edited by BN Fields, DM Knipe. New York, Raven Press, 1990, pp 1195-1228
2. Donat JF, Hable-Rhodes KH, Groover RV, Smith TF: Etiology and outcome in 42 children with acute nonbacterial meningoencephalitis. Mayo Clin Proc 1980;55:156-160
3. Tsai TF: Arboviruses. In Manual of Clinical Microbiology. 7th edition. Edited by PR Murray, EJ Baron, MA Pfaller, et al. Washington, DC, American Society for Microbiology, 1999, pp 1107-1124
4. Calisher CH: Medically important arboviruses of the United States and Canada. Clin Microbiol Rev 1994;7:89-116
Method Description Describes how the test is performed and provides a method-specific reference
Indirect immunofluorescence. Dilutions of test sera are prepared and allowed to react with substrate cells infected with Western equine encephalitis virus. If IgG antibodies to this virus are present in the serum of the patient, an antigen-antibody complex will develop that can be detected by a fluorescein-labeled antibody directed to human globulins. (Tsai TF: Arboviruses. In Manual of Clinical Microbiology. 7th edition. Edited by PR Murray, EJ Baron, MA Pfaller, et al. Washington, DC, American Society for Microbiology, 1999, pp 1107-1124; Beaty BJ, Casals J, Brown KL, et al: Indirect fluorescent-antibody technique for serological diagnosis of LaCrosse [California] virus infections. J Clin Microbiol 1982;15:429-434)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 9 a.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Same day/1 day
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
86654 x 2
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|8193||West Equine Enceph Ab, IgG, S||6957-5|
|87279||West Equine Enceph Ab, IgM, S||23587-9|