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Test ID: LCWNV West Nile Virus, Molecular Detection, PCR, Spinal Fluid

Reporting Name

West Nile Virus PCR

Useful For

Rapid testing for West Nile virus (WNV) RNA

 

An adjunctive test to serology for detection of early WNV infection

 

This assay should not be used for screening asymptomatic individuals and should only be used to test patients with signs and symptoms of West Nile virus (WNV) disease.

Clinical Information

West Nile virus (WNV) is a mosquito-borne flavivirus (single-stranded RNA virus) that primarily infects birds, but occasionally infects horses and humans. Until the virus infection was recognized in 1999 in 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. 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%) result in meningitis or encephalitis. Case 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 of age are at particularly high risk.

 

Laboratory diagnosis is best achieved by demonstration of specific IgG- and IgM-class antibodies in serum specimens. PCR testing can detect WNV RNA in plasma specimens from patients with recent WNV infection (ie, 3-5 days following infection) when specific antibodies to the virus are not yet present. However, the likelihood of detection is relatively low as the sensitivity of PCR detection is approximately 55% in cerebrospinal fluid and approximately 10% in blood from patients with known WNV infection.

Interpretation

A positive result indicates the presence of West Nile virus (WNV) RNA and is consistent with early WNV infection.

Testing Algorithm

The following algorithms are available in Special Instructions:

-Meningitis/Encephalitis Panel Algorithm

-Mosquito-borne Disease Laboratory Testing

Analytic Time

Monday through Thursday: 2 days Friday, Saturday: 3 days

Day(s) and Time(s) Performed

Monday through Saturday; Continuously 7 a.m.-8 p.m. (June through November)

Monday, Wednesday, Friday; 6 a.m. (December through May)

Clinical Reference

1. Petersen LR, Brault AC, Nasci RS: West Nile Virus: Review of the Literature. JAMA 2013;310(3):308-315

2. Busch MP, Tobler LH, Saldanha J, et al: Analytical and clinical sensitivity of West Nile virus RNA screening and supplemental assays available in 2003. Transfusion 2005;5(4):492-499

3. New York City Department of Health. West Nile surveillance and control: an update for healthcare providers in New York City. City Health Information. June 2001;20(2)

Method Name

Real-Time Polymerase Chain Reaction (PCR)/RNA Probe Hybridization

Specimen Type

CSF


Specimen Required


Container/Tube: Sterile vial

Specimen Volume: 0.5 mL

Collection Instructions: Do not centrifuge.


Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
CSF Refrigerated (preferred) 7 days
  Frozen  7 days

Reference Values

Negative

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

87798

LOINC Code Information

Test ID Test Order Name Order LOINC Value
LCWNV West Nile Virus PCR 34461-4

 

Result ID Test Result Name Result LOINC Value
SS013 Specimen Source 31208-2
86197 West Nile Virus PCR 34461-4

Forms

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

Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-CNS-Infections, mml-Pediatric, mml-Spinal-Cord