West nile virus laboratory tests
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
In 1999 in the U.S., the sensitivity of polymerase chain reaction (PCR) tests of CSF for the diagnosis of human WN encephalitis cases was only 57%; more recent statistics are currently unavailable. Thus, PCR for the diagnosis of WN viral infections of the human central nervous system (CNS) continues to be experimental and should not replace tests for the detection of WNV-specific antibody in CSF and serum, tests that are far more sensitive.
A high clinical suspicion for arboviral encephalitis should be encouraged among health care providers. When the diagnosis is in doubt, appropriate clinical specimens should be submitted to CDC or another laboratory capable of performing reliable serologic testing for antibodies to domestic arboviruses. Testing of CSF and paired acute- and convalescent-phase serum samples should be strongly encouraged to maximize the accuracy of serologic results.
Appropriate selection of diagnostic procedures and accurate interpretation of findings requires information describing the patient and the diagnostic specimen. For human specimens, the following data must accompany sera, CSF or tissue specimens for results to be properly interpreted and reported: 1) Symptom onset date (when known) 2) Date of sample collection 3) Unusual immunological status of patient (e.g., immunosuppression) 4) State and county of residence 5) Travel history (especially in flavivirus-endemic areas) 6) History of prior vaccination (e.g., yellow fever, Japanese encephalitis, or Tick-borne encephalitis viruses) 7) Brief clinical summary including clinical diagnosis (e.g., encephalitis, aseptic meningitis).
Minimally, onset and sample collection dates are required to perform and interpret initial screening tests. The remaining information is required to evaluate any specimens positive on initial screening. If possible, a convalescent serum sample taken at least 14 days following the acute sample should be obtained to enable confirmation by serological testing