ARUP's Laboratory Test Directory
| 0050514: Western Equine Encephalitis Antibody, IgG by IFA, Serum |
| Test Mnemonic: WESTERN | |
|
Methodology: Indirect Fluorescent Antibody
Performed: Tue, Fri Reported: 1-5 days |
| Specimen Required: | |
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Collect: One 4 mL SST.
Transport: 1 mL serum at 2-8°C. (Min: 0.5 mL) Submit specimen in an ARUP Standard Transport Tube. Pediatric Collection/Transport: 0.15 mL serum at 2-8°C. Remarks: Separate serum from cells ASAP. Acute and convalescent specimens must be labeled as such; parallel testing is preferred and convalescent specimens must be received within 30 days from receipt of the acute specimens. Please mark specimen plainly as "acute" or "convalescent." Unacceptable Conditions: Severely lipemic, hemolyzed, or contaminated specimens. Stability: After separation from cells: Ambient: 2 days; Refrigerated: 2 weeks; Frozen: 1 year (avoid repeated freeze/thaw cycles) |
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| Reference Interval: |
| Less than 1:16 |
| Interpretive Data: | |
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A positive result for IgG may suggest current or recent infection. Eastern equine encephalitis and western equine encephalitis viruses are both related and will show cross-reactivity. Initial infection by one of these viruses will show a specific rise in titer which is higher than titers against any other viruses of the group. A subsequent infection by another virus within this group, however, will boost the titer against the initial infecting virus (anamnestic response) and make a specific diagnosis difficult.
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| Note: | |
| Serum specimens drawn within the first two weeks after onset are variably negative for IgG antibody and should not be used to exclude the diagnosis of arboviral disease. Seroconversion between acute and convalescent sera is considered strong evidence of recent infection. The best evidence for infection is a significant change (fourfold difference in titer) on two appropriately timed specimens, where both tests are done in the same laboratory at the same time. |
| CPT Code(s): | |
| 86654 |