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Dr. Green
Diagnosis of a lower respiratory tract infection usually starts with a medical history and physical exam, but because symptoms may resemble those of a cold or influenza, diagnostic tests may be necessary. Dr. Patel, can you tell us more about diagnosing a lower respiratory infection?

Dr. Patel
Of course, Dr. Green. During the physical examination, the provider listens to the lungs with a stethoscope. In patients with a lower respiratory tract infection, the lungs may make crackling, bubbling, rumbling, or wheezing sounds.

Bronchitis and bronchiolitis are often diagnosed based only on the medical history and physical exam. But if a provider suspects pneumonia, one or more diagnostic tests may be ordered.

A chest x-ray is considered the best test for diagnosing pneumonia because it can reveal inflammation in the lungs. A chest x-ray can also show lung abscesses and fluid buildup in the space between the lungs and chest, called the pleural space. A blood test, such as a complete blood count, or CBC, can show whether the immune system is fighting an infection. However, these tests cannot provide information on what bacteria, virus, or fungus is causing the infection.

Tests that can provide this information include:

  • A blood culture
  • A sputum test, and
  • In patients with pleural effusion, when fluid builds up in the pleural space, a pleural fluid culture
Other tests may be ordered to evaluate complications of pneumonia, such as:
  • Pulse oximetry, which measures oxygen in the blood
  • Computed tomography, or CT, scan, which is an imaging test that can provide information on the extent of lung abscesses and fluid buildup in the pleural space, or
  • Bronchoscopy, which allows the provider to see inside the lungs' airways and take tissue and fluid samples