Legionnaires disease is diagnosed similarly to other types of pneumonias. Legionnaires disease is typically diagnosed through a urine test that checks for the presence of legionella antigens. In addition to this, a doctor may run other urine tests or blood tests.
Chest X-rays are common tests for individuals with Legionnaires disease. While this kind of test does not test specifically for Legionnaires disease, it is an important tool used to determine the extent of the infection of a patient’s lungs.
Finally, an important test that may be done is a sample of the sputum (phlegm) or lung tissue. This test is helpful to be able to be able to identify the source of the infection. Epidemiologists can work to link the specific type of Legionella found to a setting with a confirmed source of Legionella. This means that the sample taken from the lung of the patient would be tasted to match the environmental sample that was taken. If the samples match, or if the samples match others infected in the outbreak, Epidemiologists are able to identify the source.
Source: CDC, World Health Organization (WHO), Mayo Clinic