Laboratory Test Guide

West Nile Virus by PCR (Sendout)

General Information

Lab Name

West Nile Virus by PCR

Lab Code

RWNVP

Epic Name

West Nile Virus PCR (Sendout)

External Test Id

WNVS

Description

Useful For:

Rapid testing for West Nile virus (WNV) RNA (lineage 1 and lineage 2) using serum specimens
An adjunctive test to serology for detection of early WNV infection (ie, first few days after symptom onset)

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

Testing Algorithm:

Synonyms

Arbovirus, Flavivirus, Mosquito Borne Encephalitis, Viral encephalitis, West Nile PCR, WNV, WNVS

Components

Code	Name
RWNVPR	West Nile Virus by PCR

Interpretation

Method

Real-Time Polymerase Chain Reaction (PCR)

Reference Range

See individual components

Ref. Range Notes

Reference Values: Negative

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

Interferences and Limitations

Cautions:

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.

Whole blood rather than serum has been shown to provide increased sensitivity for detecting West Nile virus (WNV) RNA.

A negative test does not exclude infection with WNV. 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.

Guidelines

Washington DOH Notifiable Conditions

Ordering & Collection

Specimen Type

Blood

Collection

Collect 3 mL blood in GOLD TOP SST or RED TOP tube

Handling Instructions

Outside Laboratories: Centrifuge sample and transfer serum to a separate sterile vial within 6 hours of collection. Refrigerate serum.

Stability: Refrigerated (preferred): 7 days; Frozen: 7 days; Ambient: Unacceptable.

Reject Due To: Gross hemolysis, heat-inactivated specimen.

Quantity

requested: 0.5 mL serum
minimum: 0.3 mL serum

Processing

Centrifuge sample and transfer serum to a separate sterile vial within 6 hours of collection. Refrigerate serum.

Sendouts:

Order Mayo Test: WNVS.
Interfaced: Yes.

Stability: Refrigerated (preferred): 14 days; Frozen: 30 days; Ambient: Unacceptable.