Systemic and Ophthalmic Manifestations of West Nile Virus Infection

Yos Priestley; Marcia Thiel; Steven B. Koevary


Expert Rev Ophthalmol. 2008;3(3):279-292. 

In This Article

Diagnostic Tests

Suspected WNV infection is confirmed on the basis of the following laboratory tests: IgM and IgG ELISAs, plaque reduction neutralization test (PRNT), immunoflourescence (IFA) and a nucleic acid amplification test (NAT). When WNV is suspected, cerebrospinal fluid and serum samples can be tested for the presence of WNV IgM antibodies using the IgM antibody capture (MAC)-ELISA; this test is most accurate when performed 8-21 days postinfection. A more definitive diagnosis can be made if the patient exhibits a fourfold or greater increase in their IgM antibody titer in serum samples collected 2-3 weeks apart using the PRNT. In light of the fact that IgM levels are only elevated for a brief period after infection, IgG-based test kits are more often used to confirm a diagnosis of WNV, since IgG antibodies are known to persist after infection; in such an assay, a fourfold increase in IgG titer confirms a diagnosis of WNV. Commercially produced IFA kits are also available to confirm WNV, which are easier to use than PRNT. Since cross-reactivity of WNV with other flaviviruses is very common in the aforementioned-mentioned assays, it may be necessary in some cases to confirm a diagnosis of WNV using the more definitive NAT reverse transcriptase (RT) PCR test. MRI is generally performed to assess the presence and/or extent of WNV-induced lesions in patients with neuroinvasive disease, most notably paralysis.[19,20,21]


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