Sputum is a mucus-like material that is found in the lungs, and which can usually be coughed up and spit out. While no specific color key exists to diagnose an illness based on sputum color, if it is anything other than clear or white, a viral or bacterial lung infection or lung inflammation is possible. When illness is suspected in the bronchial tubes or lungs, a doctor may request a sputum test or sample to identify what is causing the infection. This is because bacteria or viruses that cause a variety of lung infections will reside in the sputum of the infected person.
Producing a sample is easy; the patient simply coughs deeply and spits into a sterile cup. A bit of the sputum will then be smeared onto a slide to produce a culture. When the patient has a difficult time producing cough sputum on his own, the doctor may have him breath in saline via a nebulizer, which works to loosen the material and makes it easier to cough up. Lung diseases and infections, like tuberculosis, lower respiratory tract infections, whooping cough, and Legionnaire's disease, are suspected based on symptoms and confirmed with a sputum test.
The results of a sputum test can take anywhere from a few hours to a few days, depending on what is found. Culture results for bacteria can be obtained rapidly, and usually do not take longer than a day, while the presence of fungus or mold can take as long as a few weeks to obtain because they require a series of tests to identify the specific mold or yeast present in the sputum. If a virus is suspected, the testing process can take anywhere from a few days to a few weeks. When bacteria are identified, a sensitivity test can be performed on the culture to determine which antibiotic is best able to treat and kill it. A culture with no growth indicates that the patient's lungs are not infected.
Sputum streaked with blood can be the result of a number of issues. While bloody sputum can be caused by something as innocuous as dry airway passages, it can also be a symptom of something more serious, such as pneumonia or even a blood clot. For this reason, it is important to consult a doctor when blood is found in the sputum, especially if other symptoms are also present.