Healthcare professionals diagnose bronchitis based on patients’ medical history and on the results of physical exams and diagnostic tests. Clinicians will ask about their history of smoking, exposure to toxic substances, and symptoms. A history of a cough lasting up to 3 weeks may indicate acute cases. A history of a cough lasting 3 months or longer may indicate a chronic condition, especially if it has occurred two years in a row.

During the physical exam, the healthcare professional will listen to the patient’s lungs for abnormal wheezing and high-pitched sounds. The doctor may then examine other parts of the body to rule out conditions that can cause respiratory symptoms, such as asthma, sinusitis (sinus infection), and influenza.

Diagnostic tests for bronchitis include:

  • Lung function tests
  • Pulse oximetry
  • Chest x-ray or CT scan
  • Blood tests
  • Sputum tests

Diagnostic Tests

Diagnosis of bronchitis usually requires a variety of diagnostic tests to help clinicians exclude other causes for the patient’s symptoms. This fact is especially true during the early stages of the disease, as it can mimic a common cold or other illnesses.

Lung Function Test

Also known as a pulmonary function test, a lung function test measures how much air the patient’s lungs can hold and how quickly the patient can exhale air out of their lungs. To undergo the test, the patient blows into a spirometer, which is a device that features a tube attached to a device that measures air.

Pulse Oximetry

Pulse oximetry measures the oxygen level of the blood. This painless test involves the placement of a clip-like device, known as a probe, on a fingertip, earlobe, or other body part. The probe uses a light to measure the amount of oxygen in the blood.

Chest X-ray or CT Scan

Healthcare providers perform chest x-rays to help rule out pneumonia and other lung problems, especially in elderly patients who may not have other signs of pneumonia. CT scans can help characterize the structure and function of the lungs. Both CT scans and chest x-rays can help providers exclude lung cancer, tuberculosis, lung infections, and other lung diseases.

Will a chest x-ray show bronchitis?

A chest x-ray will not show bronchitis, but it will show pneumonia. Bronchitis and pneumonia affect the lungs differently and these differences are apparent on a chest x-ray. Pneumonia involves fluid in the lungs, for example, and this fluid shows up on an x-ray. Bronchitis causes inflammation of the bronchial tubes, by comparison, and this inflammation cannot be seen on an x-ray. Because of these differences, a healthcare provider may order a chest x-ray when trying to determine if a patient has acute bronchitis or pneumonia.

Blood Tests

Healthcare providers sometimes order blood tests, such as complete blood count (CBC) which includes a white blood cell (WBC) count, to rule out infections. Prolactin levels may be able to help providers distinguish a bacterial infection from a non-bacterial infection, which can be helpful in guiding therapy and reducing the use of antibiotics.

Sputum Tests

A sputum test can be helpful for ruling out bacterial pneumonia or any other lower respiratory tract infection. A patient performs a sputum test by coughing up deep respiratory secretions into a sterile cup.

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