WNV PCR

Referral Lab

Lavender-top (EDTA) tube

1.0 mL

1.0 mL

Refrigerated

The sensitivity of the assay is very dependent upon the time of illness onset in which the specimen is collected.
Polymerase chain reaction testing has the greatest utility when used within the first few days of symptom onset.
A negative test does not exclude infection with West Nile virus. Therefore, the results obtained should be used in conjunction with clinical findings and serologic test results to make an accurate diagnosis.
This assay detects both viable and nonviable virus. Test performance depends on viral load in the specimen and may not correlate with cell culture performed on the same specimen.

Real-Time Reverse Transcription Polymerase Chain Reaction (RT-PCR)

West Nile virus (WNV) is a mosquito-borne flavivirus (single-stranded RNA virus) that primarily infects birds butoccasionally infects horses and humans.(1,2,3) Until the virus was recognized in 1999 in infected birds in New York City,
WNV had been detected only in the Eastern hemisphere with a wide distribution in Africa, Asia, the Middle East, and Europe. There are 2 distinct lineages of WNV: lineage 1 has the broadest distribution worldwide, including North America and Europe, whereas lineage 2 is found only in Africa and parts of Europe.
Most people who are infected with WNV do not experience symptoms. It is estimated that about 20% of those who become infected will develop West Nile fever with mild symptoms, including headache, myalgia, and, occasionally, a skin rash on the trunk of the body. About 1 of 150 WNV infections (<1%) results in meningitis or encephalitis. Fatality rates among patients hospitalized during recent outbreaks have ranged from 4% to 14%. Advanced age is the most important risk factor for death, and patients older than 70 years are at particularly high risk.
Laboratory diagnosis is best achieved by demonstration of specific IgG- and IgM-class antibodies in serum specimens.
However, polymerase chain reaction (PCR) testing can be used to detect WNV RNA in serum, whole blood, and urine specimens from patients with recent WNV infection (ie, 3-5 days following infection) when specific antibodies to the virus are not yet present. It may also be useful for patients who are immunocompromised when an antibody response is minimal or absent. Finally, PCR can be useful for supporting a serologic diagnosis, given the known cross-reactivity of WNV serology with other flaviviruses.