| Pre-Approval | None |
| Supplemental Information Requested | IgM test result for requested virus Travel history Onset date
Pregnancy status, including gestational age or estimated date of delivery Date of last unprotected sexual contact in cases of suspected sexual transmission Name and date of birth (or CalREDIE ID) of mother and infant in cases of suspected congenital transmission Symptoms and fetal ultrasound findings if available
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| Submittal Form | Specimens must be accompanied with a hard copy of the completed VRDL General Purpose Specimen Submittal Form (PDF) or a form generated in the VRDL Lab Web Portal. |
| Methodology (Commercial Test Name or Laboratory Developed Test (LDT)) | Plaque Reduction Neutralization Test or “PRNT” (LDT)
- Serum: Diagnostic
- CSF: Surveillance use only
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| Reflex Testing | None |
| Acceptable Specimen Type(s) and Collection Method | Human specimens: - Serum: Collect in serum tubes (red top) or serum separator tubes (red/gray top) and process according to the manufacturer’s recommendations to separate serum from whole blood. Aseptically transfer separated serum into sterile specimen transport tubes with secure, externally threaded closures with O-rings.
- CSF: Collect CSF in sterile specimen transport tubes with secure, externally threaded closures with O-rings (surveillance use only).
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Minimum Volume Requested
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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 and CSF (surveillance use only) specimens may be refrigerated at 2-8°C for up to 120 days or frozen at -20°C or lower for up to 1 year after collection.
Ship refrigerated specimens to VRDL on cold packs. Ship frozen specimens to VRDL on dry ice.
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Shipping Instructions | Work with your local public health department to ensure samples are packaged according to instructions for Biological Substance – 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
VRDL accepts sample deliveries 7 days/week, but for sample deliveries after business hours, or on weekends or holidays, specific consultation with VRDL is required and can be discussed on a case-by-case basis. For consultation, please contact VRDL at VRDL.submittal@cdph.ca.gov.
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| Turnaround Time | 16 Business Days |
Limitations
| 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 | Patients for whom testing is requested should be evaluated in accordance with CDPH guidance available at the CDPH Zika Information For Health Professionals webpage.
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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