Obtaining sputum involves getting a sample of a patient's phlegm by having him or her cough it up. Sputum samples are usually ordered when a patient is exhibiting pneumonialike symptoms that could be an indicator of an inhalational form of anthrax, plague, or tularemia. The sample is then stained and viewed under a microscope to look for the presence of certain bacteria. Part of the same sample is also used for a culture.
There are also more sophisticated tests that are used to identify agents, such as:
Immunoassays, which look for specific antigens or antibodies and are useful in detecting the presence of toxins. However, antibody production for identification can take time.
Gene amplification assays, such as a polymerase chain reaction, which look at the DNA or RNA to identify an agent. However, sample preparation can take a long time.
In general, detection and identification using any of these methods is dependent on the sample quantity and quality and the exactness of the processing. A combination of tests will yield the most accurate results. In the absence of immediate results, physicians who suspect bioterrorism may begin a preliminary course of treatment until the lab results are in.
How long testing should take
Unfortunately, there is no single answer to the question of how long testing will take. The testing of biological agents is complicated by several factors, which can affect the time that passes before the presence of an agent can be confirmed or a diagnosis can be made. These factors include:
Identifying the agent.Although bioterrorism is now a household term, actual incidents of bioterrorism have been rare, leaving today's physicians with limited experience in identifying these agents in the lab or treating affected patients. This means that the first patients who become sick may be mistaken for having other illnesses, thus causing a delay in the effort to test for biological agents.
Presumptive vs. confirmatory diagnoses. Not all tests are conclusive. Some tests, such as Gram stains, can give a presumptive diagnosis that an agent is present, but follow-up tests are needed. In general, presumptive diagnosis of an agent can usually be made in about a day. Confirmatory diagnosis can take two to three days.
Viral, bacterial, or toxin load. The "load" refers to how much of the agent is present in a patient. If relatively large amounts of an agent are present in a patient, cultures designed to grow the bacteria or virus could take as little as a few hours. If smaller amounts of the agent are present in a patient, these same culture tests could take up to two or three days.
Lab capabilities. Can the needed tests be done in local labs, near a suspected attack, or do the samples need to be shipped out to more advanced labs, thus affecting the overall timeline? Shipping samples to more advanced labs can tack on an extra day or two to the wait time. CDC's Laboratory Response Network helps facilitate this process.