Introduction

Understanding when to seek diagnostic testing for pulmonary sarcoidosis is an important step toward getting proper care. Many people with this condition do not experience symptoms in the early stages, which means the disease is sometimes discovered accidentally during a chest X-ray performed for another reason entirely.^[1] This can come as a surprise to patients who feel perfectly healthy.

If you do have symptoms, they might begin with general feelings of being unwell that are not specific to lung problems. These can include extreme tiredness that does not improve with rest, unexplained weight loss, slight fever, swollen lymph nodes in areas such as the chest, neck, armpits or groin, and pain or swelling in joints like the ankles.^[1] When the lungs are affected, you might notice a persistent dry cough, shortness of breath that makes everyday activities harder, mild chest pain, or wheezing.^[1][2]

It is advisable to seek medical evaluation if you experience any of these symptoms, especially if they persist or worsen over time. Because sarcoidosis can affect many parts of the body beyond the lungs, including the eyes, skin, heart, and nervous system, your doctor will want to assess whether other organs might be involved.^[3] Early diagnosis is beneficial because it allows your healthcare provider to monitor the disease and determine whether treatment is needed to prevent progression to more serious complications, such as permanent lung scarring.^[4]

Diagnostic Methods

Diagnosing pulmonary sarcoidosis is not always straightforward because the symptoms can be similar to those of many other diseases, and there is no single test that can definitively confirm sarcoidosis on its own. Instead, doctors use a combination of physical examination, medical history, imaging studies, laboratory tests, and tissue biopsies to reach a diagnosis. This process also involves ruling out other conditions that might cause similar symptoms, which is why sarcoidosis is sometimes called a diagnosis of exclusion.^[3]

Physical Examination and Medical History

Your doctor will begin by talking with you about your symptoms, how long you have had them, and whether you have any family history of sarcoidosis or exposure to substances that could trigger the disease. During the physical exam, the doctor will listen to your heart and lungs with a stethoscope, check your lymph nodes for swelling, and look for any skin changes or lesions that might indicate sarcoidosis affecting the skin.^[10] This initial assessment helps guide which tests should be ordered next.

Imaging Tests

Imaging is a cornerstone of diagnosing pulmonary sarcoidosis. A chest X-ray is often the first imaging test performed. It can reveal enlarged lymph nodes in the chest or show abnormal areas in the lungs where granulomas have formed.^[1] Based on the appearance of the chest X-ray, doctors may categorize the disease into stages that describe where the granulomas are located, though these stages do not necessarily indicate how severe the disease is or predict its course.^[2]

A computed tomography scan, or CT scan, provides much more detailed images of the lungs and chest than a standard X-ray. This test uses radiation energy to create cross-sectional pictures of internal organs and tissues, allowing doctors to see smaller granulomas and assess the extent of lung involvement more accurately.^[4][10]

In some cases, additional imaging tests may be needed. A positron emission tomography scan, known as a PET scan, or a magnetic resonance imaging scan, or MRI, might be ordered if doctors suspect that sarcoidosis is affecting the heart or the brain and nervous system. These tests help visualize inflammation and granulomas in those areas.^[3][10]

Laboratory Tests

Blood and urine tests play an important supporting role in the diagnosis. They cannot diagnose sarcoidosis by themselves, but they can provide valuable information about your overall health and how well your organs are functioning. Blood tests may check for elevated levels of certain substances that can be higher in people with sarcoidosis, and they can also assess liver and kidney function.^[10][6]

Doctors may also order blood tests to measure the amount of oxygen and carbon dioxide in your blood, which can indicate how well your lungs are working.^[4] These tests help doctors understand whether the granulomas are interfering with your lungs’ ability to deliver oxygen to your body.

Pulmonary Function Tests

Pulmonary function tests, or PFTs, measure how well your lungs move air in and out and how effectively they transfer oxygen into the bloodstream. These tests involve breathing into a machine that records the volume and flow of air. When sarcoidosis affects the lungs, it can cause the lungs to become stiff, a condition called restriction, which reduces the amount of air the lungs can hold and makes breathing harder.^[4][6] Pulmonary function tests help doctors understand the severity of lung involvement and monitor changes over time.

Heart and Eye Examinations

Because sarcoidosis can affect the heart and eyes, doctors may recommend additional tests to check these organs. An electrocardiogram, or ECG or EKG, records the electrical activity of the heart and can detect abnormalities in the heart rhythm. A cardiac ultrasound, also called an echocardiogram, uses sound waves to create moving pictures of the heart and can reveal problems with heart function.^[10][3]

An eye exam is also important because sarcoidosis can cause inflammation in the eyes, leading to symptoms such as blurred vision, eye pain, redness, or sensitivity to light. Early detection of eye involvement can prevent serious complications, including vision loss.^[3][10]

Tissue Biopsy

The most definitive way to diagnose sarcoidosis is through a biopsy, which involves taking a small sample of tissue from an affected organ and examining it under a microscope to look for granulomas. Granulomas are tiny clusters of immune cells that form when the body’s immune system overreacts to an unknown trigger.^[1][10]

In pulmonary sarcoidosis, the biopsy is most commonly taken from the lungs or the lymph nodes in the chest. However, if sarcoidosis is suspected in other parts of the body, such as the skin or the eye, a biopsy may be taken from those sites instead because they are often easier to access.^[3]

One of the most common procedures used to obtain a lung biopsy is called bronchoscopy. During this procedure, a thin, flexible tube with a camera on the end, called a bronchoscope, is passed through the nose or mouth and into the lungs. Using special ultrasound guidance, the doctor can take biopsies of the lymph nodes in the chest or collect small tissue samples from the lungs themselves.^[3] This procedure is usually done with sedation to keep the patient comfortable.

Another procedure that may be used is mediastinoscopy, which is a more invasive surgical procedure. It involves making a small incision in the chest and inserting a lighted instrument to view the space between the lungs and take biopsies of swollen lymph nodes.^[4] This is typically performed under general anesthesia as a day surgery.

In some cases, a video-assisted thoracic surgery, or VATS, may be necessary. This minimally invasive surgical approach involves inserting a tiny camera and surgical instruments through small incisions in the chest to obtain a biopsy of abnormal lung tissue. VATS allows for a definitive diagnosis while causing less pain and allowing for a quicker recovery compared to traditional open surgery.^[4]

Additional Diagnostic Procedures

Depending on your symptoms and the organs suspected to be involved, other procedures might be recommended. A bronchoalveolar lavage is a procedure where sterile saline solution is put into the lungs through a bronchoscope and then suctioned out. This sample contains cells from the smallest airways and can provide information about inflammation and help rule out infections or other lung diseases.^[4]

A six-minute walk test may be used to assess your exercise tolerance and see how well your lungs and heart are working together during physical activity. This is a simple test where you walk as far as you can in six minutes while your oxygen levels and symptoms are monitored.^[3]

Diagnostics for Clinical Trial Qualification

Clinical trials are research studies that test new treatments or ways of managing sarcoidosis. To participate in a clinical trial, patients must meet specific criteria, and diagnostic tests play a key role in determining eligibility. These tests help researchers ensure that participants have the disease and that it is safe for them to receive the experimental treatment being studied.

Standard diagnostic tests used for clinical trial qualification typically include the same imaging, laboratory, and biopsy procedures used in routine clinical diagnosis. A confirmed diagnosis of pulmonary sarcoidosis, usually supported by a biopsy showing the presence of granulomas, is often required.^[3] Chest X-rays or CT scans help researchers understand the stage and extent of lung involvement.

Pulmonary function tests are frequently used as entry criteria to assess the severity of lung disease. Researchers may require that participants have a certain level of lung function impairment to ensure that the treatment being tested is appropriate for their condition.^[4] Blood tests are also commonly performed to check organ function and ensure that participants do not have other health conditions that could interfere with the study or put them at risk.

In some clinical trials, more advanced imaging such as PET scans or cardiac MRI may be used to assess inflammation in the heart or other organs. These tests help identify patients with specific types of sarcoidosis involvement who might benefit from targeted treatments.^[3]

Before enrolling in a clinical trial, participants undergo a thorough screening process to confirm their diagnosis and assess their overall health. This process ensures that the trial is safe for them and that the data collected will be reliable and useful for advancing medical knowledge about sarcoidosis.