Tests for Pneumonia

Sh Nilica Devi *

Häggström, Mikael. "Medical gallery of Mikael Häggström 2014". Wikiversity Journal of Medicine 1 (2). DOI:10.15347/wjm/2014.008. ISSN 20018762.

Pneumonia is an infection of the lower respiratory tract caused by bacteria, viruses, or fungi. The infection can cause symptoms ranging from moderate to life threatening. Pneumonia can occur at any time of the year, but the greatest numbers of cases are seen seasonally during influenza (flu) season, typically late autumn through early spring.

Although anyone can get pneumonia, it occurs most frequently in those who are very young or over the age of 65 or people with weakened immune systems. Pregnant women and people with certain underlying conditions or damaged lungs from smoking are also at higher risk for pneumonia. This includes people who are on mechanical ventilation or chemotherapy or have received an organ donation. People with AIDS are extremely susceptible to pneumonia.

Bacteria, viruses, and fungi are microorganisms that can cause lower respiratory tract infections. Pneumonia is most often caused by a microorganism that has slipped past the body's immune defences and taken up residence deep within the lungs in the tiny structures called alveolar sacs. Bacteria are the most common cause and viruses are the second most common cause. These microorganisms may be spread to others through microscopic droplets of respiratory secretions that an infected person coughs or sneezes.

A wide range of virus, bacteria, and less (commonly) fungi can cause pneumonia, but the majority of cases are due to just a few of these.

SYMPTOMS

Pneumonia symptoms vary, depending on the age and health status of the person affected and on what microorganism caused the infection. Common symptoms include:
o Cough
o Fever and chills
o Fatigue
o Shortness of breath
o Headache
o Muscle aches
o Chest pain
o Nausea and vomiting

TESTS

The goals with testing are to determine the microorganism causing the pneumonia, to limit its spread to other people, to determine the severity of the pneumonia and to guide treatment. In a significant number of cases, it is not possible to determine the exact cause of acute pneumonia, and treatment is based upon the person's clinical presentation and medical history, the health practitioner's experience, likely microorganisms present in the community at the time, such as influenza, and on established guidelines for the care of lower respiratory tract infections. If a person's symptoms do not resolve, then additional testing may be performed to help diagnose less common pneumonia causes.

LABORATORY TESTS

Depending on the affected person's medical history and the signs and symptoms that are present at the time of the physical examination, a number of laboratory tests may be performed to help make a diagnosis. General laboratory tests include:

o Complete Blood Count (CBC) – evaluates the type and number of white blood cells; results may indicate that an infection is present.

o Basic Metabolic Panel (BMP) – blood tests for sodium, potassium and other chemistries to help determine the severity of the illness.

o Blood Gases – measures the pH and the amount of oxygen (O2) and carbon dioxide (CO2) present in a sample of blood, usually from an artery, in order to evaluate lung function.

o Bacterial Sputum Culture and Gram Stain – primary tests done to detect and identify the causes of bacterial pneumonia.

o Susceptibility Testing – performed on pathogenic bacteria grown in culture and identified by testing; used to guide treatment.

o AFB smear and Culture – performed when tuberculosis or non-tuberculous mycobacteria infection is suspected.

o Blood Culture – used to detect septicemia when it is suspected that infection has spread from the lungs to the blood or from the blood to the lungs.

Examples of tests for suspected viral pneumonia include:

o Influenza tests – used to help diagnose an influenza (flu) and sometimes to help document the presence of influenza in the community.

o Molecular tests–these tests may be used to identify the presence of bacteria and/or viruses in a respiratory sample by detecting the genetic material (DNA, RNA) of the microorganisms. These type of tests are generally very sensitive and specific and are particularly useful in detecting microorganisms that are difficult to culture.

Other types of tests that may be done depending on the affected person's history and clinical presentation include:

o Pleural Fluid Analysis – if fluid had accumulated in the space between the lungs and chest wall, the fluid may be tested to help determine the cause of infection.

o Fungal tests – done when a fungal infection is suspected; may be a culture, antigen detection or antibody tests or a molecular detection assay.

IMAGING TESTS

The search for the cause of symptoms typically begins with a physical examination. As part of the examination, a health practitioner listens to a person's lungs for abnormal breath sounds that may indicate a lung infection. This is often followed with imaging studies. These may include:

o Chest X-ray – used to detect and help evaluate the severity of a lung infection.

o CT scan – sometimes used to detect and evaluate a lung infection and to look for other non-infectious causes of a person's symptoms.