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Test ID STLP St. Louis Encephalitis Antibody, IgG and IgM, Serum

Useful For

Aiding in the diagnosis of St. Louis encephalitis

Method Name

Immunofluorescence Assay (IFA)

Reporting Name

St. Louis Enceph Ab, IgG and IgM, S

Specimen Type

Serum


Advisory Information


This assay detects only California virus. For a complete arbovirus panel, order ARBOP / Arbovirus Antibody Panel, IgG and IgM, Serum.



Specimen Required


Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.5 mL


Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
  Frozen  14 days

Clinical Information

The onset of St. Louis encephalitis is characterized by generalized malaise, fever, chilliness, headache, drowsiness, nausea, and sore throat or cough followed in 1 to 4 days by the meningeal and neurologic signs. The severity of illness increases with advancing age; persons over 60 years have the highest frequency of encephalitis. Symptoms of irritability, sleeplessness, depression, memory loss, and headaches can last up to 3 years. Areas of outbreaks since 1933 have involved the western United States, Texas, the Ohio-Mississippi Valley, and Florida. The vector of transmission is the mosquito. Peak incidence of St. Louis encephalitis is associated with summer and early autumn.

Reference Values

IgG: <1:10

IgM: <1:10

Reference values apply to all ages.

Interpretation

In patients infected with the St. Louis encephalitis 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.

 

A single serum specimen IgG of 1:10 or greater 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). While a 4-fold or greater rise in IgG antibody titer in acute and convalescent sera indicates recent infection.

 

Infections with St. Louis encephalitis 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. St. Louis encephalitis tends to produce the most severe clinical infections in older persons.

Clinical Reference

1. Gonzalez-Scarano F, Nathanson N: Bunyaviruses. In Fields Virology. Vol 1. Second 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. Seventh edition. Edited by PR Murray, EJ Baron, MA Pfaller, et al. Washington, DC, ASM Press, 1999, pp 1107-1124

4. Calisher CH: Medically important arboviruses of the United States and Canada. Clin Microbiol Rev 1994;7:89-116

Day(s) and Time(s) Performed

May through October: Monday through Friday; 9 a.m.

 

November through April: Monday, Wednesday, Friday; 9 a.m.

Analytic Time

Same day/1 day

Test Classification

This test has been cleared, approved or is exempt by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

86653 x 2

LOINC Code Information

Test ID Test Order Name Order LOINC Value
STLP St. Louis Enceph Ab, IgG and IgM, S In Process

 

Result ID Test Result Name Result LOINC Value
8182 St. Louis Enceph Ab, IgG, S 10906-6
87268 St. Louis Enceph Ab, IgM, S 10907-4

Forms

If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.

Testing Algorithm

See Mosquito-borne Disease Laboratory Testing in Special Instructions.