How Pneumonia is Diagnosed

In all types of pneumonia, diagnosis begins with a medical history, a physical examination, and a chest x-ray. The responsible organism may be identified by examining a person's phlegm under a microscope, but treatment should not be delayed while waiting for the analysis.

Other routine laboratory tests for pneumonia include a blood cell count, measurement of electrolyte levels in the blood, urinalysis, liver function tests, and blood cultures. In bacterial pneumonia, the white blood cell count is typically high, though it can fall in severe cases. By contrast, in viral or mycoplasma pneumonia, the white cell count tends to be lower or normal.

Pneumonia Prevention

While most types of bacterial pneumonia cannot be prevented, there is a vaccine that is effective against 88 percent of the bacterial strains of Streptococcus pneumoniae, preventing 80 percent of pneumococcal pneumonia cases in healthy adults. Flu vaccine has been shown to reduce the risk of viral pneumonia. The CDC recommends vaccination against both pneumococcal pneumonia and flu for the following people:

  • anyone age 65 or older;
  • people with chronic cardiovascular or lung disorders (but not those with asthma who are otherwise healthy);
  • people with diabetes or chronic liver disease or kidney disease;
  • smokers;
  • and those with a suppressed immune system due to cancer chemotherapy or conditions such as leukemia, multiple myeloma or HIV.

Even people who have already had pneumococcal pneumonia should get the pneumococcal vaccine; a Streptococcus pneumoniae infection may confer immunity to one particular strain of the bacterium, but an infection with another strain is still possible. While the vaccine used to be given only once, a booster is now recommended every five years for people who were first vaccinated before age 65. The flu vaccine should be given every autumn, and it is safe to get at the same time as the pneumococcal vaccine.

Pneumonia Treatment

The treatment for pneumonia depends on the cause. Because of practical difficulties in obtaining adequate phlegm samples and the delays in getting back the results, antibiotic treatment is often started immediately, based on the physician’s suspicions of the most likely cause. Whether someone with pneumonia needs to be hospitalized depends on the severity of the pneumonia, the individual's overall health status, and whether family members and other caregivers are able to take care of the person at home.

Antibiotics are the mainstay of treatment for bacterial pneumonia (as well as for some other types, such as mycoplasma pneumonia). The sooner treatment is started, the better. The antibiotic of choice depends on the type of bacterium responsible for the pneumonia.

At one time, penicillin was highly effective against Streptococcus pneumoniae. However, penicillin-resistant strains have become more common and newer antibiotics may be needed to treat highly resistant strains. Also, because mycoplasmas and other less common microorganisms may be the cause of the pneumonia (and the resulting symptoms may overlap with those of pneumonia caused by Streptococcus pneumoniae), combinations of antibiotics are generally prescribed.

For people who have been hospitalized with bacterial pneumonia, an early switch from intravenous to oral antibiotics (as symptoms improve) has been found to be safe and effective, allowing them to go home sooner.

Antibiotics are not effective against viral pneumonia. Most individuals with viral pneumonia recover without treatment in one to three weeks. Humidified air, supplemental oxygen, and increased fluids may be advised. In most cases, symptoms improve rapidly after treatment begins, although the speed of recovery depends on the person's previous health status.

Usually people who have pneumonia notice relief of their symptoms sooner than their doctors begin to see improvements on chest x-rays. This is especially true for older people who have multilobar pneumonia, COPD, or alcoholism.

Publication Review By: Peter B. Terry, M.D., M.A.

Published: 19 Sep 2011

Last Modified: 12 Feb 2015