Collecting Specimens for Varicella Zoster Virus (VZV) Testing
Collecting and Shipping Specimens to CDC
Providers should contact their health department to coordinate sending specimens to CDC for testing. Depending on the state health department, they may instruct providers to send specimens first to the state public health laboratory, or directly to CDC.
Review the videoExternal, which illustrates methods for collecting specimens.
Please follow these guidelines when collecting and shipping specimens for varicella-zoster virus (VZV) testing:
- You can go to the CDC Infectious Diseases Laboratories Test Directory for a list of orderable tests. Additional information and all forms can be found here: Central Website for Submitting Specimens to CDC.
- Go to the Central Website for Submitting Specimens to CDC.
- Complete and submit the CDC specimen submission form (CDC Form 50.34) and the VZV specimen collection form. The VZV specimen collection form can be accessed via CDC Form 50.34. If VZV is selected for testing within CDC Form 50.34, the link for the VZV specimen collection form will be provided.
- Please contact the CDC National VZV Laboratory with questions.
For more information about interpreting lab tests for VZV, see Interpreting Laboratory Tests.
There are two ways to prepare specimens of peripheral blood suitable for testing at CDC using VZV-specific serologic assays.
First Method: Blood Spot Method
- Prick the subject’s finger, using a lancet.
- Collect a sufficient quantity of blood onto both of the defined areas on the filter strip so that the spot expands to the circular border. (Filter strips will be made available to state and local public health laboratories and to the varicella surveillance project office in your area on request.)
- Permit the specimen to air dry completely. Do not allow different strips to come into contact with each other while wet.
- Place the strips in a sealable plastic bag. Once the blood specimens have completely dried, it is acceptable to bundle them with a rubber band and place them in a single bag. Important: Specimens must in any case be permitted to air dry completely before placing them inside a plastic bag, whether they are or are not bundled. Otherwise, bacterial or fungal growth can occur, destroying the specimen.
Handling and Shipping
- Dried blood specimens should be stored at ambient temperature. There is no need to refrigerate or freeze specimens prepared in this fashion.
- Specimens should be mailed to the laboratory by regular postal service (unless a result is urgently required) at the earliest opportunity.
Second Method: Preparation of Serum from Whole Blood
- Collect whole venous peripheral blood in serum separator vacutainer tubes.
- Permit the specimen to fully clot by standing at room temperature for at least 30 minutes.
- After the clot has formed, tubes can be centrifuged at approximately 200 X g for 5 minutes.
- The clot will have passed to the bottom of the tube and the serum fraction will be at the top, with the separator plug as a barrier between the two fractions. The serum fraction can simply be aliquoted into sterile, 0-ring seal freezing tubes using a sterile pipet.
- Freeze serum specimens at –20°C.
Handling and Shipping
- Ship specimens by overnight mail on sufficient dry ice to keep them frozen for 3 days.
- Frozen specimens obtained for larger studies may be kept indefinitely at –20°C, accumulated, and sent in batches to CDC, depending on preference.
To make a laboratory diagnosis of VZV infection using polymerase chain reaction (PCR) method, the presence of the virus DNA should be demonstrated in tissues, vesicular fluid, maculopapular lesions, or crusts from lesions. The following methods are recommended.
Polyester Swab Method
(best suited to sampling vesicular lesions)
- A sterile needle should be used to unroof the top of the vesicle.
- A sterile swab† is then used to vigorously swab the base of the lesion— applying enough pressure to collect epithelial cells without causing bleeding—and collect vesicular fluid. It is important to collect infected epithelial cells from the base of the lesion because they usually contain a significant amount of virus.
†We recommend swabs made from synthetic fibers, such as polyester, because it is difficult to elute virus from cotton swabs, and wooden swab supports usually absorb extraction buffer and inhibit PCR.
- Swabs must be placed individually into separate, empty tubes to avoid contamination. Place swabs directly into tubes. Do not place transport medium into the tube; the specimen MUST be kept dry. Tubes must be individually labeled and must be resistant to breakage.
- See Handling and Shipping PCR Specimens for shipping instructions.
Glass Slide Method
(This method is critical for the collection of material from maculopapular lesions)
- Rake the edge of the slide over the selected lesion, abrading the lesion with sufficient vigor to ensure that skin cells are gathered onto the slide. Use a sterile polyester swab to scrub the abraded lesion and (using the same swab) collect the material collected on the edge of the slide. Note: with young children, it may be less stressful if you ask them to help with this. If more than one lesion is sampled, a separate swab should be used for each one.
- Insert the swab into a tube and close it (many swabs are provided with a tube that includes a label for marking the specimen).
- Ship in a padded envelope. The swab for each sampled lesion must be placed in a separate swab tube, but multiple tubes can be shipped in the same envelope. Dry maculopapular lesion material is stable for several weeks at ambient temperature.
- See Handling and Shipping PCR Specimens for shipping instructions.
Collecting Crusts (Scabs)
Whenever present, crusts are excellent samples for PCR detection of VZV DNA. Crusts can be lifted off the skin (a glass slide is also useful for this purpose) and transferred directly into break-resistant, snap-cap or screw-top tubes. See Handling and Shipping PCR Specimens for shipping instructions.
Collecting Other Specimen Types
For some disease presentations with a suspected VZV etiology (e.g., meningitis, multi-focal organ damage), samples of cerebral spinal fluid (CSF), blood, or biopsy tissue may also be shipped. Blood or CSF can be shipped on cold packs or frozen. Biopsy tissue is preferred shipped frozen and, if available, unfixed. See Handling and Shipping PCR Specimens for additional shipping instructions.
- Dried specimens for PCR can be stored at ambient temperature indefinitely, although we prefer to receive specimens as soon after collection as possible.
- Do not refrigerate or freeze dry specimens intended for testing by PCR. Specimens can be mailed by regular post unless a result is urgently required. Do not suspend specimens in transport medium: they should be shipped dry.
In rare cases involving severe complications or death, other types of specimens (e.g., biopsied tissue, cerebrospinal fluid, peripheral blood, etc.) may be sent to the National VZV Laboratory for PCR testing. When possible, liquid specimens should be shipped frozen.
- Freezing vials: 2.0 ml polypropylene vials are available from a number of companies, including Nalgene Labware (#5000-0020), Wheaton Science Products (#985916), Corning (#430659, 431386), and Nunc (#347627).
- Plastic re-sealable bags (for containment of blood spot pads and PCR swab tubes to reduce risk of cross-contamination): 8″ × 8″ or larger bags are available from Daigger & Company, Inc (#HX28281D) and Fisher Scientific (#01-816-1E).
- Swabs with tubes: a single-unit, polyester swab with tube and slide on cap is available from Epicentre Biotechnologies (#QEC091H). Suitable swab tubes are also available on request from the CDC National VZV Laboratory.
- Filter blot pads: these pads are made to custom specifications for the CDC National VZV Laboratory. On request, CDC will supply to local and state health departments and to the varicella surveillance project office in your area.
These items are available through distributors of scientific laboratory products, such as Fisher Scientific and WVR International.
Providers should contact their health department to coordinate sending specimens to CDC for testing.
Specimens submitted to CDC for VZV testing will require 2 forms to be completed-
- the CDC specimen submission form (CDC Form 50.34) and
- the VZV specimen collection form.
The VZV specimen collection form can be accessed through CDC Form 50.34. If VZV is selected for testing within CDC Form 50.34, the link for the VZV specimen collection form will be provided. Open the form, type text into the designated boxes, print and complete. Or download, print and complete the form. You can go to the CDC Infectious Diseases Laboratories Test Directory for a list of orderable tests. Additional information and all forms can be found here: Central Website for Submitting Specimens to CDC.
Send the 2-page form and specimen to CDC VZV Laboratory. Please follow shipping and handling guidelines, as outlined above.
Note: This information applies to testing for shingles (zoster) as well as chickenpox.