Diagnosis of Idiopathic Pulmonary Fibrosis
The journey to a correct diagnosis of idiopathic pulmonary fibrosis nearly always begins at the primary care doctor’s office. Although idiopathic pulmonary fibrosis is difficult to diagnose, there is a key sign that a primary care doctor can recognize during a physical examination: Velcro®crackles. When a person with IPF breathes in, very often a doctor can hear an unusual crackling sound through the stethoscope.1,2 This sound is similar to the sound heard when gently separating the joined strip of Velcro on the blood pressure cuff. These are usually heard near the bottom part of the chest. The Velcro crackles can be heard the whole time a person with IPF breathes in.
If Velcro crackles are heard at two examinations that are several weeks apart, this is a strong clue that the patient should be referred to a lung specialist (pulmonologist) for more tests. This is especially true if the patient is 50 years old or more and has a history of smoking.
Initial Tests to Diagnose IPF
The word “idiopathic” in medical terms means “unknown cause”. In IPF, there is no known cause of the condition. Doctors are not sure why the connective tissue around the air sacs in the lung becomes stiff and scarred (fibrotic). There are many theories, but for now, IPF is a diagnosis of exclusion. That means doctors must rule out, or exclude, other conditions in order to arrive at the diagnosis of IPF.
One condition that can look like IPF is autoimmune lung disease. This may happen in a person who has rheumatoid arthritis. Another condition that can look like IPF is hypersensitivity pneumonitis, which is caused by inhaling toxic substances. Some medications can also cause side effects that mimic IPF. These include some chemotherapy drugs and the heart medication amiodarone, among others.
Very rarely, lung disease can be caused by herbal supplements used in traditional Japanese medicine. Rare cases of lung disease caused by the supplements Sho-seiryu-to and Sho-saiko-to have been reported.3,4
When a person comes in with cough, breathlessness, fatigue, and Velcro crackles, a lung specialist (pulmonologist) will perform tests. These tests will help rule out other lung conditions. The two key tests for IPF are:
- Spirometry: A test performed in the office that involves blowing or breathing into a tube attached to machinery and a computer. This test measures how much air is inhaled and exhaled, and how quickly a person can inhale and exhale. People with IPF have a restrictive pattern on spirometry. This means that their ability to breath out is fairly normal, but their ability to breath in fully is limited.5
- High-resolution computed tomography (HRCT): An imaging study performed in a medical center or hospital that involves lying down very still inside or near large, computerized equipment. Computer software is used to construct a detailed three-dimensional image from many two-dimensional x-ray images of the lungs. Most people with IPF have very distinctive lung patterns on HRCT. These signs show the formation of scar tissue around the air sacs and supportive tissues of the lungs.6
What Happens after HRCT?
HRCT is the most important test in the journey to diagnose IPF. People with IPF usually have the typical signs of the condition, which are called signs of “usual interstitial pneumonia” (UIP).
After HRCT, doctors will categorize a patient’s lungs into one of four patterns6:
- UIP: The lungs show very clear signs of UIP.
- Probable UIP: The lungs show many clear signs of UIP. They are missing one of the common signs of UIP.
- Indeterminate for UIP: The lungs show a few signs of UIP. They are missing two of the common signs OR may have non-UIP signs that are seen in other lung conditions.
- Alternate diagnosis: The lungs do not show signs of UIP. IPF is not likely.
A patient will be given the diagnosis of IPF if he or she has the symptoms of IPF (cough, breathlessness, and fatigue), plus a restrictive pattern on spirometry, plus the UIP pattern on HRCT.
When HRCT shows a “probable UIP” pattern or an “indeterminate for UIP” pattern, other tests are usually done to make sure the person has IPF.
Further Testing for IPF
There are two main tests that are used when a person is thought to have IPF, but the HRCT testing showed a “probable UIP” pattern or an “indeterminate for UIP” pattern6:
- Bronchoalveolar lavage: During this procedure, the person is either asleep under anesthesia or very heavily sedated. A tiny camera (bronchoscope) is inserted into the lungs, along with a tiny syringe tool. A small amount of saline (salt water) solution is pushed into the lungs, then suctioned up into the syringe. The fluid is sent to the pathology laboratory to be analyzed. If signs of infection or cancer are seen, then IPF is less likely. The patient should undergo other tests or treatment for infection or cancer. If no signs of infection or cancer are seen in the fluid, then IPF is still possible.7
- Lung biopsy: During this procedure, the person is asleep under anesthesia. A tiny camera (bronchoscope) and cutting tool are pushed down into the lungs. Small samples of lung tissue are cut out and sent to pathology laboratory to be analyzed. The lung tissue may show a “UIP” pattern, a “probable UIP” pattern, an “indeterminate for UIP” pattern, or an “alternate diagnosis” pattern.
A person who has the symptoms of IPF with a “UIP” pattern or a “probable UIP” pattern on lung biopsy will get the diagnosis of IPF.6
A person who has the symptoms of IPF with an “indeterminate for UIP” pattern or an “alternate diagnosis” pattern on HRCT and on lung biopsy is hard to diagnose. In those cases, it is recommended that a team of doctors have a meeting to decide what should happen. This meeting is called a multi-disciplinary discussion.8 The discussion should include a lung specialist (pulmonologist), imaging study specialist (radiologist), and laboratory specialist (pathologist). It may be that the patient is watched for several months and the tests are repeated again. At that time, the results may be more clear.
The Best Outcomes Happen at a Tertiary Center
The best outcomes for patients happen when they are seen at a big medical center or hospital (tertiary center) that specializes in IPF. If you or a loved one have symptoms of IPF, like cough, breathlessness, and fatigue, it is important to make an appointment with a lung specialist (pulmonologist) at a tertiary center. This is especially true if a doctor has told you that there are signs of IPF like Velcro crackles and a restrictive pattern on spirometry.
References and Further Reading
- Cottin V, Cordier JF. Velcro crackles: the key for early diagnosis of idiopathic pulmonary fibrosis? Eur Respir J. 2012;40(3):519-21.
- Sellarés J, Hernández-González F, Lucena CM, et al. Auscultation of Velcro crackles is associated with usual interstitial pneumonia. Medicine (Baltimore). 2016;95(5):e2573.
- Tsuchiya K, Toyoshima M, Suda T. Pneumonitis with diffuse alveolar hemorrhage induced by Sho-seiryu-to. Intern Med. 2017;56(19):2623-2626.
- Tomioka H, Hashimoto K, Ohnishi H, et al. An autopsy case of interstitial pneumonia probably induced by Sho-saiko-to. Nihon Kokyuki Gakkai Zasshi. 1999;37(12):1013-8.
- Moore, VC. Spirometry: step by step. Breathe. 2012;8:232-240.
- Raghu G, Remy-Jardin M, Myers JL, et al. An official ATS/ERS/JRS/ALAT clinical practice guideline. Am J Respir Crit Care Med. 2018;198(5):e44-e68.
- Pesci A, Ricchiuti E, Ruggiero R, De Micheli A. Bronchoalveolar lavage in idiopathic pulmonary fibrosis: what does it tell us? Respir Med. 2010;104 Suppl 1:S70-3.
- Tomassetti S, Piciucchi S, Tantalocco P, Dubini A, Poletti V. The multidisciplinary approach in the diagnosis of idiopathic pulmonary fibrosis: a patient case-based review. Eur Respir Rev. 2015;24(135):69-77.