Diagnosis

How IPF is diagnosed?

Physicians will use a variety of diagnostic strategies to come to a diagnosis of idiopathic pulmonary fibrosis (IPF) depending on the individual medical history and symptoms that patients present with. These usually include one or more of the following tests:

History and Physical Exam: The physician should take a detailed history to learn if there were any environmental, occupational, familial, or other medical conditions that could have contributed or predisposed a person to the diseases’ development. When listening to the lungs with a stethoscope, the physician may hear ‘crackles’ or Velcro-like sounds with the stethoscope. These are ‘opening’ sounds made by the small airways during inspiration. About 50% of patients with IPF may have “clubbing” of the fingertips. This is a widening of the fingertips due to a lack of oxygen in the blood. This is not specific to IPF and occurs in other lung disorders, heart disease, and can also be present from birth.

Chest X-Ray: A routine chest x-ray may be used as a screening test. However, 5-15% of patients with significant scarring will have a normal chest x-ray, and IPF cannot be diagnosed from chest x-ray alone.

High Resolution Computerized Tomography (HRCT): This test provides sharper and detailed image of your lungs to help a physician more clearly identify certain clinical patterns in your lung tissue that may indicate disease; in IPF, a radiologist may identify a “honeycombing” pattern that suggests lung scarring and damage to the air sacs, or “ground-glass opacity”, which refers to the hazy appearance of lung tissue that is most associated with inflammation.

Pulmonary Function Tests: These are breathing tests that measure the lungs’ ability to exchange oxygen and carbon dioxide properly. These tests are usually done in a hospital or clinical laboratory and consist of breathing into a spirometer, and are sometimes done in a “body box” which looks like a glass telephone booth. There are two important components to a Pulmonary Function Test: (1) Spirometry, which measure inspired and expired lung volumes and the rate at which this occurs, and (2) diffusion capacity, or DLco, which measures the ability of oxygen to diffuse into the blood stream.

Pulse Oximeter: This is a screening test which indicates the amount of oxygen in the blood. A device is placed on the finger or earlobe. The oximeter transmits light at different wavelengths through small blood vessels. Normal ranges are 95-100% on room air. Pulse oximetry does not measure carbon dioxide levels so a blood gas level measurement may be necessary in some patients.

Arterial Blood Gas (ABG): A direct measurement of arterial pH, oxygen, and carbon dioxide through a direct arterial puncture. Arterial blood has recently been oxygenated by the lungs and thus indicates how much oxygen is available to the body. Venous blood has a lower oxygen concentration and indicates how much oxygen has been extracted.

Bronchoscopy: This involves an examination of the main airways of the lungs through the use of a small, flexible tube called a bronchoscope. Brochoscopy helps to evaluate lung problems or blockages and provides a means to sample tissue or fluids. Unfortunately, the lung tissue samples obtained through bronchoscopy are small and are usually inadequate for definitive diagnoses.

Bronchoalveolar lavage (BAL): BAL is done through the bronchoscope and is a way to remove a tiny sampling of cells from the lower respiratory tract. A small amount of saline is injected through the bronchoscope and when withdrawn removes a small sample of cells from the respiratory tract. Usually this is not helpful in making the diagnosis of IPF but may beneficial in other clinical situations.

Surgical Lung Biopsy: Surgical lung biopsy is the most revealing diagnostic tool in the evaluation of patients suspected of having idiopathic pulmonary fibrosis and is considered the “gold standard.” Since there are many diseases that mimic IPF, and since there can be significant differences in the treatment and prognosis, it is important to get a correct diagnosis. A lung biopsy in conjunction with the HRCT can also help determine how far the disease has progressed. Usually the biopsy can be obtained minimally invasively with video assisted thoracoscopic surgery (VATS). VATS is usually well tolerated, but it may not be recommended for all individuals.

Exercise testing: Typically performed with a six-minute walk test (6MWT), exercise testing is used to measure how well the lungs respond to exertion. The methods used for exercise testing vary from hospital to hospital, but usually include the use of a stationary bike or treadmill. Blood pressure, EKG and oxygen saturation levels (recorded by an electronic device placed on the ear or finger) are monitored during exercise.