| Pre-Approval | None |
| Supplemental Information Requested | Requested: Travel history, onset date, IgM test result for requested virus
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| Submittal Form | Specimens must be accompanied with a hard copy of the completed āVRDL General Purpose Specimen Submittal Formāā (PDF) or a form generated in the VRDL Lab Web Portal. |
| Methodology (Commercial Test Name or Laboratory Developed Test (LDT)) | Plaque Reduction Neutralization Test (LDT)(Surveillance Use Only)
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| Reflex Testing | None |
| Acceptable Specimen Type(s) and Collection Method | Human specimens: - Serum:
- Plain Red-Top Tubes: Serum collected in plain, red-top tubes must be separated and transferred to sterile, screw-cap tubes for storage and transport.
- Serum Separator Tubes (SST): SST may be transported after centrifugation.
- CSF: Collect CSF in sterile, screw-cap tubes
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Minimum Volume Requestedā
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| Transport Medium (if using) | Not Applicable |
| Specimen Labeling | Each specimen tube must be labeled with at least two unique patient identifiers, e.g., patient full name and date of birth. |
| Storage & Preservation of Specimen / Shipping Conditions | - Separated Serum: Refrigerate or freeze separated serum promptly after collection.
- Serum Separator Tubes: Refrigerate, do not freeze.ā
- CSF: Refrigerate or freeze CSF promptly after collection.ā
Ship refrigerated specimens to VRDL on cold packs. Ship frozen specimens to VRDL on dry ice. |
Shipping Instructions | Work with your local public health department to ensure samples are packaged according to instructions for Biological Substance ā Category B (UN 3373) shipment. Ship specimens and a hard copy of the completed submittal forms to: CDPH VRDL ATTN: Specimen Receiving 850 Marina Bay Parkway Richmond, CA 94804 Phone: 510-307-8585
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| Turnaround Time | 16 Business Days |
Limitationsā
| When available, CSF as well as serum should be submitted.
A negative result does not rule out infection.
PRNT is often performed with paired viruses that are closely related and geographically co-circulating. When neutralizing antibodies are detected for two or more closely related viruses, a four-fold or greater difference in titer is presumed to indicate the identity of the exposure; however, due to the possible persistence of neutralizing antibodies and memory B-cells from prior infection(s), such determinations cannot rule out the possibility of an anamnestic antibody response.
PRNT may be used to confirm recency of infection with a four-fold, or greater difference in titer between acute and convalescent specimens collected at least two weeks apart.
Laboratory results with clinical and environmental correlation must be used together with current case definitions to confirm or rule out cases.
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| Additional Information | West Nile and St.āāāāā Louis Encephalitis Viruses in California: Guidelines for Human Testing, Surveillance, and Reporting (PDF)
A convalescent specimen is recommended to help determine recency of infection. When submitted separately, be sure to identify the previously submitted specimen by the VRDL accession number so that the acute and convalescent specimens may be linked, tested to endpoint and interpreted as a pair.
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| VRDL Points of Contact | Medical and Epidemiology Liaisons: (510) 307-8585 or VRDL.submittal@cdph.ca.gov
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