Submitting Specimens for Anthrax Testing

Key points

  • Consult with your state health department and CDC to obtain authorization before you ship samples for anthrax testing.
  • Laboratory and clinical staff should follow specific instructions for collecting and processing samples that require anthrax testing.
  • Follow packaging and shipping regulations and requirements for anthrax specimens to protect people from exposure.
Writing on checklist

Special alerts

Obtain authorization‎

Do not ship any specimens or samples without first consulting with and obtaining authorization from your state health department and CDC. Contact CDC's Emergency Operations Center at 770-488-7100 to coordinate anthrax testing and for further shipping instructions.

Specimen acceptance criteria

Health Department Consultation

Before shipping specimens for anthrax testing, clinics or laboratories must first obtain authorization from both their state health department and CDC. Health department point of contacts can be found here. CDC's Emergency Operations Center can be reached at 1-770-488-7100 to coordinate anthrax testing and to provide shipping instructions.

CDC accepts specimens from state public health laboratories and other federal agencies for analysis. Specimens from private healthcare providers and institutions must first be submitted to the city, county, or state health department laboratory for appropriate processing.

Collecting anthrax specimens

Most anthrax testing is done on serum. To collect serum for anthrax testing, follow these steps:

  1. Collect 10 mL of blood aseptically from a peripheral vein using a needle and a Vacutainer™ serum separator tube (SST). This will yield approximately 5 mL of serum.
  2. Allow the collected blood to sit at room temperature for at least 30 minutes, but no longer than 60 minutes. The clot should be completely formed within 30 minutes.
  3. Centrifuge the specimen before storing or shipping to completely separate serum from the blood cells. Centrifuge serum according to manufacturers' instructions for the tube in use.
  4. After centrifuging the serum, use sterile technique to divide and transfer at least 1 mL of serum into each of two plastic freezing vials with a leak-proof screw-cap.
  • One sample should be shipped to the state or local health department or CDC for testing.
  • The other sample should be retained and frozen as a "backup sample" in case the original shipment is lost or is unsuitable for testing upon arrival at CDC.
  • 1 mL is the minimum acceptable volume needed by CDC.

5. Label the plastic vial(s) with all the following:

  • Patient name and/or identification number;
  • Specimen collection date and time; and
  • Whether the sample is an "acute" or a "convalescent" specimen.

6. Freeze the serum immediately after it has been transferred into the plastic freezing vial(s).
7. Store the specimen at -20° C or colder until it is shipped to CDC.]

Note that for field collections of blood where serum separation is not possible within 60 minutes of collection, store the specimen at 4°C using cold packs. Ideally, ship the sample to a laboratory with centrifugation capabilities as soon as possible and ideally in less than 24 hours.

Timing of specimen collection

Testing for Lethal Factor Toxin

An acute sample to test for lethal factor (LF) toxin can be collected from zero to 18 days after suspected exposure or the onset of symptoms. Earlier collection and testing is preferred due to the steady but gradual declines in toxin levels during antimicrobial therapy.

Serology testing

Serology testing should only be conducted on paired serum samples, which are submitted at the same time and include an acute (up to 7 days after symptom onset) and a convalescent phase (14–35 days after symptom onset) specimen. It is recommended that the convalescent-phase specimen be taken two weeks after the acute specimen.


Freeze the serum immediately after it has been transferred into the plastic freezing vial(s). Store the specimen at -20° C or colder until it is shipped to CDC.

Specimen packaging

Laboratory staff must handle, package, and label samples in accordance with regulations to ensure they and others are kept safe from potential exposure to anthrax. When samples need to be packaged and shipped for anthrax testing, specific procedures should be followed. Take the following steps when packaging specimens for anthrax testing.

  1. Insert absorbent material (such as absorbent sheets) into a sealable plastic bag, and then place the plastic vial(s) containing serum specimens in that bag, too (bag #1). Seal the bag.
  2. Line a leakproof secondary packaging container, such as an appropriate plastic screw-top canister (shipping canister), with absorbent material. Use enough absorbent material to absorb the entire contents of the plastic vials in case of a leak or spill.
  3. Place the sealed plastic bag into the shipping canister. Place a biohazard label on the outer surface of the shipping container.
  4. Place dry ice into a polystyrene foam-lined box (the overpack[A]). Use at least 6 pounds (about 3kg) of dry ice for each day of shipping time; at least 12 pounds (about 6 kg) is required for overnight shipment (2 days).
  5. Divide the weight of the ice in pounds by 2 to get the approximate weight in kg.
  6. Place the shipping canister into the overpack. 7.) Place an itemized list of contents and the CDC Form 50.34 inside a second plastic bag (bag #2).
  7. Seal and place the bag inside the overpack.

Important guideline‎

Do not put any paperwork in the bag containing the specimens (bag #1) or in the shipping canister.

Specimen shipping

The U.S. Department of Transportation Hazardous Materials Regulations and the International Air Transport Association (IATA) Dangerous Goods Regulations state that the following labels and markings should be placed on one side of the overpack:

  1. "UN 3373 Biological substance, Category B" marking
  2. "Miscellaneous Class 9" label (dry ice label with 9 at the bottom of the diamond) - This label should include the dry ice marking: "UN 1845 Carbon dioxide, solid (dry ice)" where you must list the weight of the dry ice (in kg) included in the box. Divide the weight of the ice in pounds by 2 to get the approximate weight in kilograms.
  3. "OVERPACK" – This indicates that secondary packaging has been placed in an outer box with dry ice.
  4. Name and telephone number of person responsible for shipment. This person must be knowledgeable about the shipment and know how to remediate in case of spill or leakage.
  5. Two sets of "Double up Arrows" – Place one set on the same side of the box as the shipping labels, and another set on the opposite side of the box.